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    • 专利摘要:
    The invention relates to a system (10) for generating skyrmions comprising: - a gun (12) having a wall region (14) made of a first material, the region (14) defining an outer space (16) made in a second material distinct from the first material and an interior space (18) made of a third material distinct from the first material, the second material and the third material being magnetic materials, and - a reversing device (26) of the own magnetic magnetization reversing the magnetic magnetization at the interface between the region (14) and the interior space (18).
    公开号:FR3025655A1
    申请号:FR1402021
    申请日:2014-09-09
    公开日:2016-03-11
    发明作者:Vincent Cros；Horne Noah Van；Joao Sampaio；Albert Fert；Nicolas Reyren
    申请人:Centre National de la Recherche Scientifique CNRS；Thales SA；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a system for generating magnetic skyrmions.
    [0002] Magnetic skyrmions are used in the field of spintronics. As a reminder, the spintronic domain, also called spin-electron domain, is a field of electronics using the spin of the electron and not only the charge, for the processing of information. Such magnetic memory systems are, for example, mass storage systems, shift registers, logic systems and analog memories, for example for neuro-inspired type circuits. All of these spintronic element (s) memory systems, which have the advantage of being nonvolatile, compatible with CMOS (or Complementary Metal Oxide Semiconductor) technology, are an electronic component manufacturing technology and, by extension , all the components manufactured according to this technology) and resistant to electromagnetic radiation, are based on a spintronic element called Magnetic Tunnel Junction (MTJ) which is a stack consisting mainly of two thin magnetic layers (a few nanometers) separated by an insulating layer (of the order of a nanometer) or by a spin valve (in English denoted SV) in which all layers are metallic. For a spintronic element of binary memory type, the bit of the memory corresponds to a MTJ (or SV, respectively) of a few tens to a few hundred nanometers, whose state, alternatively 0 and 1, is obtained by two possible configurations of the relative direction of the magnetizations in the two magnetic layers (Parallel or Antiparallel). The memory state is read by measuring the voltage at the terminals of the MTJ thanks to the tunneling effect of magnetoresistance, also called TMR. The writing of the state is performed, in the last generation of element (called STT-MRAM), by spin transfer effect (Spin Transfer Torque in English, noted STT) which allows to act on the direction of a (or) magnetization (s) and thus to change their configuration by injection of a spin polarized current, passing from Parallel to Antiparallel or vice versa, without the need to apply a magnetic field. In more complex systems such as shift register systems or spintronic memristors, state changes are based on the controlled displacement of magnetic domain walls. In the same way as for the binary memory spintronic elements, the reading is performed by magnetoresistive effect and the writing is done by spin transfer effect, which in these spintronic binary memory elements makes it possible to move the domain walls. . Several technical problems remain to be solved in the existing technologies of spintronic element memory systems. First, it is necessary to reduce the energy consumption associated with the writing of information. Indeed, the energy cost has increased with the decrease of the dimensions of the components. This increase is related to the need to preserve or even increase the efficiency of the spin transfer effects that are used to write information (by reversing the direction of magnetization) and the increased influence. natural or nanofabrication-related defects that require the injection of increasing current densities to achieve non-stochastic write regimes. It is also desirable, while reducing the power consumption (used for the various functions of the memory), to preserve a measured signal strength sufficient for good memory state detection. Secondly, it is necessary to increase the density of information that can be stored in non-volatile spintronic memories, which could be done either by increasing the level of integration (ie decreasing the size of the individual bit) or by going beyond beyond standard memory architectures that are binary.
    [0003] One solution is to have multi-state memories, also called multi-level memories. However, in the existing magnetic memories, the switching between two different directions of the uniform magnetizations allows to code only one bit per memory element. The existence of multi-state memories would greatly increase the storage density and reduce the cost.
    [0004] For this, it is desirable to use magnetic skyrmions. Magnetic skyrmions are chiral spin structures (that is, asymmetric with respect to a mirror-like inversion) with a non-trivial topology and whose size can be extremely small (up to a few atomic meshes) and the direction of rotation between the spins is imposed. The configuration of these spin structures can be of the "hedgehog" type (see FIG. 1 where the arrows indicate the orientation of the organized spins in concentric circles r1, r2, r3, r4 and r5)) or "vortex" (cf. Figure 2 where the arrows indicate the orientation of organized spins in concentric circles R1, R2, R3, R4 and R5). Such chiral magnetic structures have been predicted and observed in crystals such as MnSi, FeCoSi or FeGe having a crystalline structure with inversion symmetry breaking which allows the manifestation of a magnetic interaction called Dzyaloshinskii-Moriya ( DM) and characterized by a parameter named D, giving rise to the stabilization of magnetic configurations of skyrmion type. In magnetic thin film systems, inversion symmetry breaking enabling the stabilization of a chiral magnetic structure is induced by the presence of an interface between a magnetic thin film and a thin spin-coupled high-orbit film (further called SOC or spin-orbit interaction), which generates a strong DM interaction, giving rise to stabilization of skyrmion-type magnetic configurations. We recall that the SOC describes the interactions between the spin of a particle 10 (the electron in our case) and its motion, and is of particular importance in magnetism, and particularly in spintronics, to explain a certain number of fundamental properties of materials such as, for example, magnetic anisotropies, magnetoresistive effects or magnetization relaxation processes.
    [0005] It will be appreciated that the skyrmions are topologically protected and thus relatively stable to changes in external parameters; they can not be transformed (once stabilized) to transit to another magnetic order (quasi-uniform or vortex for example). As indicated previously, the magnetic skyrmions were observed only in 2009 in systems of single crystal type (MnSi, FeCoSi, FeGe ...) having a lack of inversion symmetry related to the crystalline structure. These so-called massive systems can not be strongly reduced in thickness (of the order of a few tens of nanometers), are not compatible with CMOS technologies and especially do not present the phase comprising ultra-dense networks of skyrmions at low temperature and under magnetic field.
    [0006] In addition to the orbital spin interaction, other types of magnetic interaction, for example dipolar interactions, may make it possible to stabilize skyrmion-type magnetic configurations in nanostructures, which are then called magnetic bubbles which may have In the present document, particularly in the following description and claims, we group together under the general name of magnetic skyrmion, the structures of magnetic thin film systems, a hedgehog spin structure, as shown in FIG. schematized in FIGS. 1 and 2. Thus, it is desirable to be able to generate skyrmions in a controlled and efficient manner.
    [0007] However, this is not sufficient since, for the proper functioning of skyrmion-based systems, it is necessary to be able to control the topological number and the chirality of skyrmions because these parameters directly determine a set of skyrmion properties, for example their direction of displacement under current but also their response to external radio frequency excitation. There is therefore a need for a skyrmion generation system for generating skyrmions with a given topology and chirality. For this, there is provided a skyrmion generation system comprising a gun having a wall region made of a first material, the region delimiting an outer space made of a second material distinct from the first material and an interior space made in a third material. material distinct from the first material, the second material and the third material being magnetic materials, the region having a bottom wall and a side wall in connection with the bottom wall at a junction area. The barrel also has a half-bubble creation zone capable of generating half-bubbles, the creation zone being in the interior space. The creation zone comprises at least one of two elements: one or more defects of the wall and a part of the junction zone. The barrel also includes a half-bubble treatment zone comprising an outlet in communication with the outer space, the exit being suitable for transforming half-bubbles into skyrmions, and a half-bubble propagation passage, the connecting passage. the creative area at the exit. The treatment zone is able to limit the contact between the creation zone and the output being also suitable for transforming the half-bubbles into skyrmions. The system also includes a magnetization reversal device capable of reversing the magnetic magnetization at the interface between the region and the interior space. The reversing device is selected from the group consisting of a first current injection unit in a first transverse direction, the first unit being adapted to inject into the half-bubble generation zone a spin-polarized current with a direction spin polarization having a non-zero component along a second transverse direction, the first transverse direction and the second transverse direction being perpendicular to a longitudinal direction along which the barrel extends, a first unit injecting current in a first transverse direction, the first unit being adapted to inject into the half-bubble generation zone a spin polarized current with a spin polarization direction having a non-zero component along a longitudinal direction along which the barrel extends, the first transverse direction being perpendicular to the longitudinal direction of a unit for applying a magnetic field outside the half-bubble creation zone, a heating unit of the half-bubble creation zone and an application unit of an electric field outside the half-bubble creation zone.
    [0008] According to particular embodiments, the generating system comprises one or more of the following features, taken singly or in any technically possible combination: the part of the junction zone is a part in which the angle between the bottom wall and the side wall is less than or equal to 180 °. At least one of the second magnetic material and the third magnetic material is selected from the group consisting of a ferromagnetic layer interfaced with a non-magnetic layer, the ferromagnetic layer comprising at least one of Fe, Co or Ni, a ferromagnetic perovskite single or double base based Ti, Cr, Mn, Fe, Co, Mo or Ru, a Heusler alloy based on Fe, Co, Ni or Mn, a magnetic semiconductor or a magnetic alloy containing an element Rare Earths (Sm, Gd, Tb or Er for example), a non-magnetic layer comprising at least one of the elements Pt, W, Ir, Re, Ta, Pb, Bi, Rh, Pd, Mo, Cu, Sm, Gd, Tb or Er, said non-magnetic layer being interfaced with a ferromagnetic layer or a stack of ferromagnetic (s) and / or non-magnetic layers, and a magnetic material having an absence of symmetry of inversion. the device for reversing the magnetic magnetization is the first current injection unit, the system further comprising a second current injection unit in the first transverse direction, the second current injection unit being capable of injecting into the propagation passage a spin-polarized current with a direction of spin polarization different from the direction of spin polarization of the current which the first unit is adapted to inject. the propagation passage comprises two portions connected by an elbow. the system is capable of generating skyrmions having an extension, the output having a geometrical shape of which at least one dimension is greater than the extension of a skyrmion that the system is capable of generating. the system is capable of generating skyrmions with an extension, the propagation passage having a width greater than or equal to half the extension of a skyrmion that the system is capable of generating. The system is capable of generating skyrmions having an extension, the propagation passage having a length greater than or equal to the extension of a skyrmion that the system is capable of generating. the third material has a third exchange length, the width of the side wall being greater or equal if the first material is a magnetic material having a first exchange length, at the first exchange length, if the first material is a magnetic conductive material, at the spin diffusion length, and whether the first material is insulating or vacuum, at the characteristic tunneling length. The third material has a third exchange length, the creation zone being writable in a circle having a radius less than or equal to the third exchange length. Other features and advantages of the invention will appear on reading the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are: FIG. a type of skyrmion structure, FIG. 2, a view of another type of skyrmion structure, FIG. 3, a schematic representation of a top view of an exemplary skyrmion generation system, FIG. 4, a schematic representation of a top view of an example of a system for generating skyrmions in operation, FIG. 5, a schematic representation of a top view of an example of a system for generating skyrmions in operation, FIG. 6, a diagrammatic representation of a top view of an example of a skyrmion generation system showing the characteristic dimensions, FIG. 7, a diagrammatic representation of a side view of an exemplary system of g FIG. 8 is a diagrammatic representation of a side view of another example of a skyrmion generation system, FIG. 9, a diagrammatic representation of a side view of another example of a generation system. FIG. 10 is a diagrammatic representation of a top view of another example of a skyrmion generation system. FIG. 11 is a diagrammatic representation of a top view of another example of a generation system. Skyrmions, - Figure 12, a schematic representation of a top view of another example skyrmions generation system, 5 - Figure 13, a schematic representation of a top view of another example of a generation system FIG. 14 is a diagrammatic representation of a top view of another example of a skyrmion generation system, and FIG. 15 is a diagrammatic representation of a top view of another example of a skyrmion generation system. FIG. Skyrmion generation system With reference to FIG. 3, a skyrmion generation system 10 is proposed. The generation system 10 is a system capable of generating skyrmions. Skyrmions that the generation system 10 is able to generate have an extension noted R in the following. More specifically, in the context of the description, the extension R of a skyrmion is the size of a relaxed skyrmion such that this extension is defined by equation 18 in the article S. Rohart et al. Phys. Rev. B 88, 184422 (2013) depending on the parameter D, among others.
    [0009] The R extension is measurable by magnetic or magneto-optical imaging techniques. The parameter D entering in the definition of the extension R can be obtained from the measurement of the wall displacement speeds under field or under current for example. The extension of the individual skyrmions, that is to say in finite number, in non-dense networks, is determined by the competition between the different energy terms of the nanostructure (related to the exchange interaction and DM interactions) and can reach ultimate dimensions for a magnetic object of a few atomic meshes (see Heinze, S. et al., Nature Phys., 7, 713-718 (2011)). The generation system 10 comprises a gun 12.
    [0010] The barrel 12 is an elongated member extending mainly along a longitudinal direction. Two transverse directions perpendicular to the longitudinal direction are also defined, the first transverse direction being also perpendicular to the second transverse direction. The longitudinal direction and the two transverse directions are respectively symbolized by an X axis and two Z and Y axes 35 in FIG.
    [0011] The barrel 12 has a wall region 14 made of a first material M1, the region 14 delimiting an outer space 16 made of a second material M2 and an interior space 18 made of a third material M3. The barrel 12 also has a half-bubble creation zone 20, a treatment zone 21 having an outlet 22 and a propagation passage 24 connecting the creation zone 20 to the outlet 22. A half-bubble is a magnetic domain whose direction of magnetization is reversed with respect to the direction of magnetization in the remainder of the interior space 18 and which is in contact with the region 14.
    [0012] The first material M1 is distinct from the second material M2. The first material M1 is also distinct from the third M3. For example, according to one embodiment, the first material M1 is a non-magnetic material. According to another embodiment, the first material M1 is the ambient medium, the region 14 being in particular obtained by a cutout made in a layer forming the outer space 16. According to another embodiment, the three materials M1, M2 and M3 are magnetic materials. The first material M1 has properties very different from the second material M2 and the third material M3.
    [0013] In such a case, this means that the magnetic parameters of the first material M1 are different from the magnetic parameters of the second material M2, which themselves may or may not be different from the magnetic parameters of the third material M3. Magnetic anisotropy, the thickness of the material or the presence of inversion symmetry breaking are examples of easily modifiable parameters.
    [0014] According to one embodiment, the wall 14 is manufactured by etching on a magnetic material. According to another embodiment, the wall 14 is obtained by rendering a non-magnetic magnetic material. According to the embodiment illustrated in FIG. 6, the wall 14 has a bottom wall 30 and a side wall 28 in connection with the bottom wall 30 at a junction zone 32. The second material M2 in which the outer space 16 is made is a magnetic material. In particular, the second magnetic material M2 forms, according to one embodiment, a quasi-two-dimensional hybrid system (because the second material M2 3025655 9 has film thicknesses of some atomic planes which are much smaller than the other dimensions of the system) comprising a nanostructure composed of at least one stack of an ultra-thin layer of ferromagnetic material and a layer of a metal, non-magnetic, high SOC. Typically, the thickness of the high SOC layer is between 0.2 nanometers (nm) and 10 nm. In one embodiment, the ultrathin magnetic film is replaced by a stack of layers comprising ferro-magnetic (s) layers (and possibly non-ferromagnetic layers), for example Co / Ni / Co / Ni, where Co denotes Cobalt. and Ni, but symmetry breaking at one or more of the interfaces with a high SOC material is preserved For example, according to one embodiment, the second material M2 is a ferromagnetic layer interfaced with a non-magnetic layer, the ferromagnetic layer comprising at least one of iron (Fe), cobalt (Co) or nickel (Ni), a multilayer with perpendicular magnetization, a single or double ferromagnetic perovskite based on Ti, Cr, Mn, Fe , Co, Mo or Ru, a Heusler type alloy based on Fe, Co, Ni or Mn, a magnetic semiconductor, for example GaMnAs, magnetic organic layers or a magnetic alloy containing a rare earth element (Sm, Gd, For example, a Heusler type alloy is a ferromagnetic metal alloy based on a Heusler phase, an intermetallic phase of particular composition, having a face-centered cubic crystallographic structure. Typically, the thickness of the ferromagnetic layer (s) is of a few atomic planes, and is between 0.2 nm and 3 nm. According to another embodiment, the second material M2 is a non-magnetic layer comprising at least one of the elements Pt, W, Ir, Re, Ta, Pb, Bi, Rh, Pd, Mo, Cu, Sm, Gd. , Tb or Er, said non-magnetic layer being interfaced with a ferromagnetic layer or a stack of ferromagnetic (s) and / or non-magnetic layers. Platinum (Pt), tungsten (W), iridium (Ir), rhenium (Re), tantalum (Ta), lead (Pb), bismuth (Bi) are elements of column 5d of the periodic classification of the elements; rhodium (Rh) and palladium (Pd) belong to column 4d; Molybdenum (Mo) and copper (Cu) are elements of column 3d and samarium (Sm), gadolinium (Gd), terbium (Tb) or erbium (Er) are rare earth elements. It should be noted that alloys of the above elements are also possible, as well as stacks such as Bi / Ag (Ag represents silver) or Au / Ag where Au represents gold.
    [0015] According to another embodiment, the second material M2 is a magnetic material having a lack of inversion symmetry. MnSi, CoFeGe or FeGe are examples of magnetic materials having a lack of inversion symmetry.
    [0016] In all embodiments, the second material M2 of the outer space 16 has a second exchange length A2. The second exchange length A2 is, for example, measured by a magnetic resonance technique. The second material M2 also has a second magnetic anisotropy K2. The second magnetic anisotropy K2, by way of example, is measured by a magnetometric measurement. The third material M3 in which the interior space is made is a magnetic material. The same remarks as for the second magnetic M2 also apply for the third magnetic M3. These remarks are therefore not repeated in what follows. In all the embodiments, the third material M3 of the interior space 18 has a third exchange length A3 if the third material M3 is different from the second material M2. The third exchange length A3 is, for example, measured by a magnetic resonance technique.
    [0017] The third material M3 also has a third magnetic anisotropy K3. The third magnetic anisotropy K3, by way of example, is measured by a magnetometric measurement. According to the example of FIG. 6, the width m of the side wall 28, that is to say the dimension of the side wall 28 along the second transverse direction Y, depends on the nature of the first material M1 . When the first material M1 is a magnetic material having a first exchange length, the width m of the side wall 28 is greater than or equal to the first exchange length. When the first material M1 is a magnetic conducting material, the width m of the side wall 28 is greater than or equal to the spin diffusion length. When the first material M1 is insulating or vacuum, the width m of the side wall 28 is greater than or equal to the tunneling characteristic length (typically 1 nm). According to one embodiment, the second magnetic material M2 and the third magnetic material M3 are identical. The creation zone 20, also called the nucleation zone, is able to generate half-bubbles.
    [0018] 3025655 11 The half-bubbles are also called by some authors of half-skyrmions. The creation zone 20 is in the interior space 18. According to the example of the embodiment illustrated in FIG. 6, the creation zone 20 is a part of the junction zone 20 in which the angle between the bottom 30 5 and the side wall 28 is equal to 90 °. Advantageously, the creation zone 20 is writable in a circle whose radius F is less than or equal to the third exchange length A3 of the third material M3. According to the embodiment illustrated in FIG. 6, the creation zone 20 also includes a defect 34 of the wall 14. A defect is a protuberance or notch of size greater than or equal to the third exchange length A3 of the third M3 material. The shape of the defects 34 greater than or equal to the exchange length A3 is related in particular to the roughness of the edges of the wall 14 during manufacturing processes. The shape can be obtained by near field microscopy imaging or by transmission electron microscopy. The processing zone 21 is suitable for carrying out the transfer of the half-bubbles that the creation zone 20 is able to generate towards the outlet 22, or even for storing half-bubbles that the creation zone 20 is capable of generating.
    [0019] In the particular example of FIG. 3, it is the outlet 22 which is able to limit the contact between the region 14 and the half-bubbles that the creation zone 20 is able to generate. The outlet 22 is in communication with the outer space 16. The outlet 22 is also suitable for transforming the half-bubbles into skyrmions.
    [0020] According to the embodiment of FIG. 4, the output 22 has a geometric shape of which at least one dimension is greater than the extension R of a skyrmion that the generation system 10 is capable of generating. The propagation passage 24 connects the creation zone 20 to the output 22. The propagation passage 24 is able to propagate the half-bubbles 30 generated by the creation zone 20 towards the output 22. The displacement of a determined number of half-bubbles is operated by spin transfer effect, for example spin-polarized current injection geometry, perpendicular to the layers or in the plane of the high SOC layer, or by application of a local electric field .
    [0021] The spin polarization acting on the half-bubble (s) by virtue of the spin-transfer effect can be obtained by the spin-spin coupling couples linked to the spin Hall effect, by the Rashba effect (terms transfer torque are directly related to spin-orbit effects (SOC) in the non-magnetic metal) or more conventionally using a magnetic tunnel junction. The peculiarity of these spin transfer terms is that they make it possible to apply these pairs to advance the one or more half-bubbles in the propagation passage 24. Given the energy advantages expected for skyrmion propagation systems by geometry perpendicular spin injection (J. Sampaio et al., Nature Nanotechnology 8, 839, 2013), the system 10 is intrinsically suitable for integration into such systems. For a propagation passage 24 of a few tens of nm in width, half-bubble speeds of a few tens of m / s can be obtained by spin transfer effect, corresponding to current densities of a few MA / cm 2.
    [0022] It is thus possible to move half-bubble trains without noticeably changing their sizes, nor the distance between two neighboring half-bubbles. It should be noted that in addition, the shape of the half-bubbles and the displacement of spin-induced half-bubbles in the propagation passage 24 is always possible with a curvature of the propagation passage 24.
    [0023] The propagation passage 24 has a dimension d along the longitudinal direction X called length and a dimension along the second transverse direction Y called width I. The length d of the propagation passage 24 is greater than or equal to the extension R of a skyrmion that the system 10 is clean to generate.
    [0024] The width I of the propagation passage 24 is greater than or equal to half the extension R of a skyrmion that the system 10 is capable of generating. The generation system 10 also comprises a reversing device 26 of the magnetic magnetization capable of reversing the magnetic magnetization at the interface between the region 14 and the interior space 18.
    [0025] As schematically shown in FIG. 7, according to one embodiment, the overturning device 26 is a first current injection unit in the first transverse direction Z. The first injection unit 26 is suitable for injecting at the creation zone 20 a spin polarized current with a spin polarization direction having a non-zero component along a second transverse direction Y.
    [0026] Such a first injection unit 26 is, for example, an assembly of three layers as shown in FIG. 7. FIG. 7 represents an assembly of four layers 40, 42, 44, 46 aligned along the first transverse direction Z, a layer 44 corresponding to the system 10 and the other layers 40, 42, 46 corresponding to the first injection unit 26. From top to bottom, the first layer 40 is an upper electrode, the second layer 42 is a spin polarizing layer, the third layer 44 corresponds to the system 10 and the fourth layer 46 is a lower electrode. Preferably, the other layers 40, 42, 46 corresponding to the first injection unit 26 have the same geometry as the layer 44 corresponding to the system 10. Another embodiment is shown in FIG. 8, the first layer 40 is a higher electrical contact and the fourth layer 46 is a lower electrical contact.
    [0027] According to another embodiment illustrated in FIG. 9, instead of an assembly of three layers, the first injection unit 26 is an assembly of two layers 48, 50 surrounding the layer 44 corresponding to the system 10. such configuration, from top to bottom, the first layer 48 is a spin polarizing layer and the second layer 50 is a spin drain. The first layer 48 is thus a spin polarizing layer 20, which is not necessarily magnetic but has a strong spin-orbit coupling which makes it possible to generate a strong spin-polarized spin spin effect current. The operation of the generation system 10 is now described with reference to FIGS. 4 and 5 which are diagrammatic representations of a top view of an exemplary skyrmion generation system in operation.
    [0028] The injection works on the basis of a destabilization of the magnetization in the zone of creation 20. The degree of such a destabilization of the magnetization in the creation zone 20 is in fact related to the value of the magnetization. angle between the bottom wall and the side wall. Plus, the angle between the bottom wall and the side wall is closed, plus the magnetization in the creation zone 20 is destabilized and promotes overturning.
    [0029] In addition, a spin polarized current is injected in perpendicular geometry. The non-zero component along the second transverse direction Y of the spin polarization direction of the spin polarized current injected by the reversing device 26 generates the spin transfer torque component enabling the reversal of the magnetization in the area. of creation 20.
    [0030] The nonzero component along the second transverse direction Y of the spin polarization direction of the spin polarized current injected by the reversing device 26 allows the half bubble to be displaced once created in the propagation passage 24. to exit 22.
    [0031] The polarized current injection can be done in different ways. According to a first embodiment, the current is injected with temporal variations. For example, three different current densities are used. The injection of a current at the first current density induces the reversal of the magnetization in the zone of creation 20. The injection of a current at the second density lower than the first density allows the propagation of the current. half-bubble formed. The injection of a current at the third density stronger than the second density facilitates the transformation of the half-bubble into skyrmion. According to a second embodiment, the current is injected with spatial variations. For example, two different current densities are used, a first density for the creation zone 20 and a second density for the propagation passage 24. According to a third embodiment, the current is injected with variations in the direction of propagation. spin polarization. The third embodiment is combinable with the first embodiment and / or the second previous embodiment (s). The output 22 finally allows the controlled separation of the half-bubbles and the formation of magnetic skyrmions of non-trivial topology. Since the orientation of the magnetic moments in the walls of the half-bubbles (their chirality) is fixed by the spin polarization of the injected current and the magnetization of the system, all the bubbles formed are skyrmions having a topological number well. determined: either S = 1, or S = -1 (but never a mixture of both). This ensures that all skyrmions created by the system 10 behave identically. The description of the operation of the system 10 shows that the system 10 has multiple analogies with microfluidics phenomena. As examples, in the following, three interesting analogies are highlighted. The first analogy concerns the surface energy of magnetic bubbles. As with fluidic bubbles, the free energy of magnetic bubbles is minimized for a maximum ratio of volume on surface (or area on circumference). This is responsible for the soft and predictable closure of the magnetic bubble as it exits the treatment zone 21, since the relaxation to a circular configuration induces the separation of the back portion of the bubble from the fluidic outlet. The second analogy relates to the phenomenon of "anchorage". At the exit of a microfluidic channel, the affinity between the transported fluid and the injector can prevent the separation of liquid bubbles. Such a phenomenon is found in the form of a meniscus on the walls of a glass of water. The simulations indicate a similar phenomenon in the affinity of the half-bubbles for the edges. Indeed, it is for this reason that the fluidic outlet has a shape that favors a detachment with a minimum of "magnetic wetting".
    [0032] The third analogy concerns the variant with the time variation of the injected current. As for a micro-fluidic injector, an excessive current density in the treatment zone 21 results in the formation of long "feathers" of the reversed phase at the outlet 22 of the treatment zone 21. Depending on the ratio of the In the interior of the treatment zone 21 and the external current existing outside the barrel 12, these "feathers" may either swell locally at the outlet or become long feathers carried away by the external current. The barrel 12 can thus be described as a "magneto-fluidic" gun with magnetic skyrmions. The system 10 makes it possible to obtain the stabilization of a controlled number of skyrmions 20 in a nanostructure. Indeed, the system 10 is reproducible, allows the control of the position and the moment at which the skyrmion is created as well as the control of the chirality of the skyrmion. Indeed, the system 10 allows the formation of magnetic skyrmions of non-trivial topology, that is to say of topological number S = 1 or S = -1. All formed bubbles are skyrmions having a well-defined topological number: either S = 1, or S = -1 but never a mixture of the two. Reformulated in terms of the write operation, the system 10 ensures reproducibility, magnetic purity (no undesired configuration is produced), spatial accuracy, time accuracy and deterministic character (once triggered , 30 the writing is done at a definite moment). The system 10 thus makes it possible to generate skyrmions in a controlled manner. Such a controlled generation paves the way for the use of skyrmions in controlled numbers, in particular for nonvolatile electronic memories and multilevel memories for the storage of information and reprogrammable magnetic logic.
    [0033] 3025655 16 However, the use of skyrmions in controlled numbers offers multiple advantages. In particular, the dimensions of the skyrmions (being defined by competitions between different energy terms of the systems considered and therefore controllable) can reach ultimate limits of the order of a few atomic meshes (less than 5 nanometers), which allows to answer the problem of increasing the density of stored information. In addition, the internal structure of skyrmions renders them a priori much less sensitive to structural and / or magnetic defects due for example to nano-fabrication, and thus facilitates their displacement, by spin transfer effect, thus reducing the energy cost of operation of a memory device using skyrmions. The controlled generation of skyrmions also concerns the field of bioinspired circuits due to memristive properties. In addition, magnetic skyrmions, like other magnetic solitons, are described as particles or pseudo-particles and thus can be used as oscillators or resonators for highly integrated radiofrequency (RF) systems. For example, among the lower energy excited modes for a skyrmion, the gyrotropic mode or the beat mode that have frequencies in the GHz range are examples. The system 10 also has the advantage of being compact because the dimensions of the barrel 12 are of the order of the size of the skyrmions generated, that is to say from a few nanometers to a few tens of nanometers. In addition, the system 10 is achievable using standard techniques of electronic lithography and ion etching. In general, a creation zone 20 is a zone which, by virtue of its specific geometry, favors the destabilization, and hence the local reversal, of magnetic spins. Indeed, the geometry of the creation zone 20 makes it possible to control the magnetic interactions that play a role in the nucleation of skyrmions, such as the exchange interaction, the asymmetric exchange interaction linked to spin-orbit coupling, called Dzyaloshinskii interaction. - Moriya (DM), or the dipolar interaction.
    [0034] In the following, to better understand the influence of the geometry of the creation zone 20, the origin and the role of each of the aforementioned interactions are recalled. The exchange interaction tends to strongly align the neighboring spins (parallel in a ferromagnetic or antiparallel in an antiferromagnetic). To locally reverse a magnetization, it is generally necessary to reverse that of a part of its neighboring atoms. Therefore, reversing the magnetization of an atom having few neighbors requires a lower energy than that of an atom having more magnetic neighbors. The shape of the creation zone 20 shown in FIGS. 12 and 13 minimizes the number of atoms around certain regions, especially the corners of the creation zone 20.
    [0035] The dipolar interaction tends to align the 'north' pole of a set of atoms with the 'south' pole of a set of neighboring atoms. Such interaction causes the magnetic atoms on either side of the barrel 12 to radiate a dipolar field acting on the atoms inside the barrel 12, tending to reverse their magnetization. The atoms inside the barrel 12 thus undergo a destabilization dependent on the strength of the dipolar field, especially since their stabilization by the exchange interaction is greatly diminished. In the case where the magnetic material is of low structural symmetry or a very thin film in contact with a material film with strong spin-orbit coupling, a third interaction is to be considered: the so-called Dzyaloshinskii-Moriya (DM) interaction. This third interaction, equivalent to an asymmetric exchange interaction, tends to open the angle between neighboring spins. One consequence of the presence of the DM interaction is that the spins on the edge of magnetic layers have an angular offset with respect to the angle imposed by the direct exchange interaction. The creation zone 20, whether this zone comprises a wedge or a defect, functions by minimizing the local exchange interaction, maximizing the local demagnetizing (dipolar) field, and making use of spin-spin interactions. orbit type DM to exalt and guide the local magnetization reversal. As a result, alternatively, the angle between the bottom wall and the side wall is different from 90 °.
    [0036] In particular the angle between the bottom wall and the side wall is less than or equal to 180 °. The Applicant has verified in particular by numerical simulations that the optimization of the destabilization of the magnetization in the creation zone 20 by reducing the angle between the bottom wall and the side wall can be made by reducing the angle between the bottom wall and the side wall provided that the confining effects due to the approach of the edges do not become predominant (that is, to the point of hindering the creation of half-bubbles in the interior space 18 ). Figure 12 illustrates a shape of the triangular bottom wall in section promoting the formation of half-bubbles.
    [0037] According to another embodiment, the third magnetic material M3 has a shape of the chiral interaction DM which is suitable for stabilizing the skyrmions of the type shown schematically in FIG. 2. In such an embodiment, the first injection unit 26 is capable of injecting into the creation zone 20 a spin polarized current 5 with a spin polarization direction having a non-zero component along the X direction. Alternatively, the reversing device 26 is an application unit of A magnetic field outside the zone of creation 20. Typically the magnetic field that the application unit is suitable to apply is a few tens of milliTesla (mT) 10 to a few hundred mT. According to another variant, the overturning device 26 is a heating unit of the creation zone 20. For example, the overturning device 26 is a laser source making it possible to locally destabilize the magnetization only at the level of the creation zone 20 .
    [0038] According to another variant, the overturning device 26 comprises a unit capable of applying an electric field in the creation zone 20. Other embodiments for the treatment zone 21 of the half-bubbles exist provided that the treatment zone 21 is able to limit the contact between the region 14 and the half-bubbles that the creation zone 20 is clean to generate.
    [0039] Indeed, the formation of skyrmions having a particular chirality is strongly influenced by the phenomenon of "magnetic wetting". The treatment zone 21 makes it possible to limit the magnetic wetting and thus ensures the formation of skyrmions at the outlet 22 of the system 10. According to the case illustrated in FIG. 10, the reversing device 26 of the magnetic magnetization is the first unit In addition, the generation system 10 includes a second current injection unit 50 in the first transverse direction Z. The second current injection unit 50 is adapted to injecting into the transformation passage 24 a spin polarized current with a direction of spin polarization different from the direction of spin polarization of the current than the first unit 26 is capable of injecting. This means that, according to the example of FIG. 10, there are two different portions 52, 54 in the propagation passage 24, the first portion 52 comprising the creation zone 20 and the second portion 54 comprising the exit 22. first portion 52, the direction of polarization of the spin allows the creation of a half-bubble while in the second portion 54, the direction of the spin polarization is chosen so that the half-bubble comes off the barrel 12 in the second portion 54 (reduction of wetting). In such a case, preferably, the outlet 22 has a simpler shape than in the other embodiments since the outlet 22 is no longer constrained to ensure the limitation of the contact between the region 14 and the half-bubbles that the Creative Zone 20 is clean to generate. According to the example of Figure 11, the propagation passage 24 comprises two portions 56, 58 connected by a bend 60. In the example of Figure 11, the first portion 56 and the second portion 58 10 are rectilinear. In addition, the first portion 56 is oriented in the longitudinal direction X while the direction in which the second portion 58 extends is at an angle to the longitudinal direction X. In this case, the angle between the direction in which s extends the second portion 58 and the direction in which the first portion 56 extends is obtuse. Such a geometry of the propagation passage 24 makes it possible at the same time to maintain the optimal conditions for the injection into the creation zone 20 and to allow the ejection of the half-bubble not on one of the arms at the exit of the barrel 12 but in the center of the barrel 12.
    [0040] For this, the elbow has a suitable angle. The angle of the bend is chosen according to the polarization direction of the spin of the current injected by the first unit 26. In such a case, the output 22 has a simpler shape than in the other embodiments since the output 22 n is more constrained to ensure the contact limitation between the region 14 and the half-bubbles that the creation zone 20 is able to generate. In addition, as the "magnetic wetting" observed in the applicant's simulations is partly a function of the angle between the concerned edges and the propagation trajectory of skyrmions, various geometric shapes are possible for the output 22. In particular, triangular shapes, square shapes or rounded shapes. More specifically, the outlet 22 is formed by two cylinders whose base has a shape varying according to the embodiments. In the case of Figures 4, 6, 11 and 12, each cylinder has a triangular base, the outlet 22 being symmetrical.
    [0041] According to the example of FIGS. 5 and 10, one of the two cylinders has a triangular base, the other has a rectangular base. In the case of Figure 13, each cylinder has a rectangular base, one of the two bases having a section greater than or equal to twice the section of the other base. In the case of FIG. 14, each cylinder has the same rectangular base, the cylinders being symmetrical with respect to the axis of symmetry of the barrel 12. In the case of FIG. 15, each cylinder has the same ovoid base, the cylinders being symmetrical with respect to the axis of symmetry of the barrel 12.
    [0042] In all cases, the maximum dimensions of the bases are a few times the dimension R of a skyrmion. Typically, each dimension is less than or equal to three times the dimension R of a skyrmion. The modes of operation and embodiments described above are capable of being combined with each other, totally or partially, to give rise to other embodiments of the invention.
    权利要求:
    Claims (10)
    [0001]
    A system (10) for generating skyrmions comprising: a gun (12) comprising: - a wall region (14) made of a first material, the region (14) defining an outer space (16) formed in a second material distinct from the first material and an interior space (18) made of a third material distinct from the first material, the second material and the third material being magnetic materials, the region (14) having a bottom wall (30) and a wall lateral section (28) in connection with the bottom wall (30) at a junction zone (32), - a zone of creation (20) of half-bubbles suitable for generating half-bubbles, the zone of creation (20) being in the interior space (18), the creation zone (20) comprising at least one of the following two elements: - one or more defects (34) of the wall (14), and - a part of the junction zone (32) and a treatment zone (21) of the half-bubbles s comprising: - an output (22) in communication with the outer space (16), the outlet (22) being adapted to transform the half-bubbles into skyrmions, and - a propagation passage (24) of the half-bubbles, the passage (24) connecting the creation zone (20) to the outlet (22), the treatment zone (21) being able to limit the contact between the creation zone (20) and the outlet (22) being also clean transforming the half-bubbles into skyrmions, and a reversing device (26) for the magnetic magnetization capable of reversing the magnetic magnetization at the interface between the region (14) and the interior space (18), the device reversing member (26) being selected from the group consisting of: - a first current injection unit in a first transverse direction, the first unit being adapted to inject into the zone of creation of half-bubbles a spin-polarized current with a spin polarization direction with a non-zero component g a second transverse direction, the first transverse direction and the second transverse direction being perpendicular to a longitudinal direction along which extends the barrel (12), - a first current injection unit in a first transverse direction the first unit being adapted to inject into the half-bubble generation zone a spin polarized current with a spin polarization direction having a non-zero component along a longitudinal direction along which extends the barrel (12), the first transverse direction being perpendicular to the longitudinal direction, - a unit for applying a magnetic field outside the half-bubble creation zone, - a heating unit for the creation zone of half-bubbles, and - a unit for applying an electric field outside the half-bubble creation zone. 10
    [0002]
    The system of claim 1, wherein the portion of the junction zone (32) is a portion in which the angle between the bottom wall (30) and the side wall (28) is less than or equal to 180 °. 15
    [0003]
    3.- System according to claim 1 or 2, wherein at least one of the second magnetic material and the third magnetic material is selected from the group consisting of: - a ferromagnetic layer interfaced with a non-magnetic layer, the ferromagnetic layer comprising at least one of Fe, Co or Ni, a single or double base ferric perovskite based on Ti, Cr, Mn, Fe, Co, Mo or Ru, a Heusler alloy based on Fe, Co, Ni or Mn, a magnetic semiconductor, a magnetic organic layer or a magnetic layer containing rare earth elements. a non-magnetic layer comprising at least one of the elements Pt, W, Ir, Re, Ta, Pb, Bi, Rh, Pd, Mo, Cu, Sm, Gd, Tb or Er, said non-magnetic layer being interfaced; with a ferromagnetic layer or a stack of ferromagnetic (s) and / or non-magnetic layers, and - a magnetic material having a lack of inversion symmetry. 30
    [0004]
    4. The system of claim 3, wherein the reversing device (26) of the magnetic magnetization is the first current injection unit, the system (10) further comprising a second injection unit of current in the first transverse direction, the second current injection unit being adapted to inject into the propagation passage (24) a spin polarized current with a spin polarization direction different from the spin polarization direction of the current that the first unit is clean to inject.
    [0005]
    The system of any one of claims 1 to 4, wherein the propagation passage (24) comprises two portions connected by a bend.
    [0006]
    6. System according to any one of claims 1 to 5, wherein the system (10) is adapted to generate skyrmions having an extension, the output having a geometric shape of which at least one dimension is greater than the extension a skyrmion that the system (10) is clean to generate.
    [0007]
    7. A system according to any one of claims 1 to 6, wherein the system (10) is adapted to generate skyrmions having an extension, the propagation passage (24) having a width greater than or equal to half of 15 the extension of a skyrmion that the system (10) is able to generate.
    [0008]
    8. System according to any one of claims 1 to 7, wherein the system (10) is adapted to generate skyrmions having an extension, the propagation passage (24) having a length greater than or equal to the extension of a skyrmion that the system (10) is capable of generating.
    [0009]
    9. A system according to any one of claims 1 to 8, wherein the third material has a third exchange length, the width (m) of the side wall (28) being greater than or equal to 25 - if the first material is a magnetic material having a first exchange length, at the first exchange length, - if the first material is a magnetic conductive material, at the spin diffusion length, and - if the first material is insulating or the empty, at the tunnel effect characteristic length.
    [0010]
    10. System according to any one of claims 1 to 9, wherein the third material has a third exchange length, the creation zone (20) being writable in a circle having a radius less than or equal to the third length. 35 exchange.
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    同族专利:
    公开号 | 公开日
    EP3192106B1|2018-10-24|
    EP3192106A1|2017-07-19|
    FR3025655B1|2016-10-14|
    WO2016038113A1|2016-03-17|
    US20170256351A1|2017-09-07|
    US10102956B2|2018-10-16|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JP2014086470A|2012-10-19|2014-05-12|Institute Of Physical & Chemical Research|Skyrmion drive method and micro element|
    FR3009420B1|2013-08-01|2016-12-23|Thales Sa|MEMORY DEVICE COMPRISING AT LEAST ONE SPINTRONIC ELEMENT AND ASSOCIATED METHOD|
    US9773540B2|2015-07-17|2017-09-26|The Johns Hopkins University|Skyrmion based universal memory operated by electric current|WO2016159017A1|2015-03-31|2016-10-06|国立大学法人東北大学|Magnetic resistance effect element, magnetic memory device, manufacturing method, operation method, and integrated circuit|
    KR101746698B1|2016-03-07|2017-06-14|울산과학기술원|Skyrmion diode and method of manufacturing the same|
    JP6712804B2|2016-11-18|2020-06-24|国立研究開発法人理化学研究所|Magnetic element, skyrmion memory, central arithmetic processing LSI equipped with skyrmion memory, data recording device, data processing device and data communication device|
    CN106877858A|2016-12-27|2017-06-20|南京大学|A kind of logic gates based on magnetic Skyrmion|
    KR101875931B1|2017-07-07|2018-07-06|울산과학기술원|Meteal structure for forming skyrmion and method for forming skyrmion in metal structure|
    CN108538328B|2018-03-07|2021-11-02|北京航空航天大学|Data writing method of magnetic memory|
    US10777247B1|2019-03-25|2020-09-15|International Business Machines Corporation|Spin-based storage element|
    KR102166769B1|2019-09-30|2020-10-16|서울대학교산학협력단|Spin-Hall-effect-modulation Skyrmion Oscillating Device|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1402021A|FR3025655B1|2014-09-09|2014-09-09|SKYRMION GENERATION SYSTEM|FR1402021A| FR3025655B1|2014-09-09|2014-09-09|SKYRMION GENERATION SYSTEM|
    EP15762594.8A| EP3192106B1|2014-09-09|2015-09-09|Skyrmion generation system|
    PCT/EP2015/070657| WO2016038113A1|2014-09-09|2015-09-09|Skyrmion generation system|
    US15/508,982| US10102956B2|2014-09-09|2015-09-09|Skyrmion generation system|
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