Weak domain wall pinning ferrimagnetic material and applications thereof

Abstract

The application relates to the technical field of ferrimagnetic materials, in particular to a weak domain wall pinning ferrimagnetic material and application thereof. The application provides a weak domain wall pinning ferrimagnetic material, which comprises 0-100% of transition elements, 0-100% of rare earth elements and 0-100% of doping elements according to the atomic percentage, the total of the transition elements, the rare earth elements and the doping elements is 100%, the atomic percentage of the transition elements in the weak domain wall pinning ferrimagnetic material is greater than that of the rare earth elements and the doping elements, the atomic percentage of the rare earth elements and the doping elements in the weak domain wall pinning ferrimagnetic material is not 0, and the doping elements comprise boron and / or nitrogen. The weak domain wall pinning ferrimagnetic material has greatly reduced magnetic domain wall pinning site density and strength, and can reduce the current density and the magnetic field strength required for driving the magnetic domain wall to move.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ferrimagnetic materials, and particularly relates to a weak domain wall pinning ferrimagnetic material and application thereof. BACKGROUND

[0002] The development of traditional silicon-based semiconductor logic chips is gradually approaching its physical limit, and the continuation of Moore's Law is facing severe challenges. Spin logic devices have intrinsic non-volatile storage characteristics, can realize storage and computing integration, and thus break through the technical bottleneck of speed and power consumption of the Von Neumann architecture, becoming an important field of focus in the current academic and industrial circles. Among numerous new spintronic devices, spin logic devices based on domain wall motion can realize rich logic operation functions, and are one of the important technical paths for developing spin logic chips. Traditional ferromagnetic materials have large stray fields, and the magnetic moment is sensitive to external magnetic fields, resulting in reduced integration and reliability of spintronic devices based on ferromagnetic materials. At the same time, the spin dynamics of ferromagnetic materials is generally in the nanosecond scale, limiting the further improvement of the response speed of the devices. In contrast, ferrimagnetic materials (FiM) have a small net magnetization due to the existence of two anti-parallel magnetic sublattices inside, and at the magnetic compensation temperature, the magnetic moments of the two sets of magnetic lattices cancel each other out, and the macroscopic net magnetic moment is zero, greatly reducing the stray field; at the angular momentum compensation temperature, the angular momenta of the two sets of magnetic lattices cancel each other out, and the macroscopic net angular momentum is zero, at which time the ferrimagnetic material exhibits excellent spin dynamics characteristics, such as higher SOT efficiency, longer spin coherence length, and ultrafast magnetic dynamics, which can reduce the energy consumption and response speed of spintronic devices. Experimentally, the angular momentum and magnetic compensation temperature of ferrimagnetic materials can be directionally regulated by various methods, and thus they have unique advantages in the application field of new spin devices based on domain wall motion.

[0003] In the application of racetrack magnetic memory, domain wall pinning can seriously affect the movement of the domain wall, increase the magnetic field strength and current density required to drive the domain wall movement, and reduce the reliability and durability of the memory device. Therefore, people have begun to focus on methods to reduce domain wall pinning. However, existing racetrack memories use ferrimagnetic or doped magnetic metals, which have a large density and strength of domain wall pinning sites. SUMMARY

[0004] The purpose of the present application is to provide a weak domain wall pinning ferrimagnetic material and application thereof, which greatly reduces the density and strength of the magnetic domain wall pinning sites, and can significantly reduce the magnetic field strength and current density required to drive the domain wall movement.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The application provides a weak domain wall pinning ferrimagnetic material, which comprises 0-100% of transition elements, 0-100% of rare earth elements and 0-100% of doping elements in terms of atomic percentage, the total of the transition elements, the rare earth elements and the doping elements is 100%, and the atomic percentage of the transition elements in the weak domain wall pinning ferrimagnetic material is greater than that of the rare earth elements and the doping elements, and the atomic percentage of the rare earth elements and the doping elements in the weak domain wall pinning ferrimagnetic material is not 0.

[0007] The doping elements comprise boron and / or nitrogen.

[0008] Preferably, the ferrimagnetic material is in an amorphous structure.

[0009] Preferably, the transition elements comprise one or more of Fe, Co and Ni.

[0010] Preferably, the rare earth elements comprise one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y.

[0011] Preferably, the transition elements are Co, the rare earth elements are Gd, and the doping elements are B.

[0012] Preferably, the atomic percentage of Co in the weak domain wall pinning ferrimagnetic material is 10.0%-80.0%, the atomic percentage of Gd in the weak domain wall pinning ferrimagnetic material is 10.0%-80.0%, and the atomic percentage of B in the weak domain wall pinning ferrimagnetic material is 10.0%-80.0%.

[0013] Preferably, the atomic ratio of Co to B is 9:1-3:1.

[0014] The application further provides an application of the weak domain wall pinning ferrimagnetic material in a magnetic storage spintronic device, a magnetic logic spintronic device, a magnetic field sensor or a novel soft magnetic material.

[0015] The application provides a weak domain wall pinning ferrimagnetic material, which comprises 0-100% of transition elements, 0-100% of rare earth elements and 0-100% of doping elements in terms of atomic percentage, the total of the transition elements, the rare earth elements and the doping elements is 100%, the atomic percentage of the transition elements in the weak domain wall pinning ferrimagnetic material is greater than that of the rare earth elements and the doping elements, and the atomic percentage of the rare earth elements and the doping elements in the weak domain wall pinning ferrimagnetic material is not 0; and the doping elements comprise boron and / or nitrogen. The ferrimagnetic material (Fi M) has a small net magnetization due to the existence of two anti-parallel magnetic sublattices in the ferrimagnetic material. At the angular momentum compensation temperature, the angular momenta of the two sets of magnetic lattices offset each other, and the macroscopic net angular momentum is zero. At this time, the ferrimagnetic material exhibits excellent spin dynamics. The doping elements reduce the number and strength of pinning sites in the ferrimagnetic material. After the doping elements enter the alloy, the distance between the magnetic atoms is changed, the bond length and coordination number are changed, the strength of the exchange interaction is changed, the grain refinement is realized, the amorphization effect is improved, the grain boundary and pinning are reduced, and thus the magnetic field strength and current density required for driving the domain wall motion are greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A high-resolution cross-sectional TEM image of the weak domain wall pinning ferrimagnetic material described in Example 1 (30.2%);

[0017] Figure 2 XAFS images of the weak domain wall pinning ferrimagnetic material described in Example 1 (30.2%), Co, Co described in Comparative Example 1 80 B 20 and Co described in Comparative Example 2 76 Gd 24 ;

[0018] Figure 3 A relationship curve diagram of the domain wall moving speed and the magnetic field, the current density of the weak domain wall pinning ferrimagnetic material described in Example 3 (19.1%), Example 4 (21.6%), Example 5 (25.1%), Example 6 (28.2%), Example 7 (29.2%) and Example 1 (30.2%) in a racetrack device;

[0019] Figure 4 A relationship curve diagram (a) of the domain wall moving speed and the magnetic field intensity and a relationship curve diagram (b) of the domain wall moving speed and the current density of the weak domain wall pinning ferrimagnetic material described in Example 1 (30.2%) in a racetrack device at different temperatures;

[0020] Figure 5Comparison of effective unpinning field and pinning density characterization of the weak domain wall pinned ferrimagnetic material described in Example 1 (30.2%) and other materials (Co, CoB, CoFeB, FeTb, GdMnAs, Co, CoFeB and CoGdB) in Hall rod devices;

[0021] Figure 6 The pinning site density (a) and pinning site strength (b) of the weak domain wall pinned ferrimagnetic materials described in Examples 3 (19.1%), 4 (21.6%), 5 (28.2%), 6 (29.2%), and 1 (30.2%) were characterized.

[0022] Figure 7 Domain walls of different configurations of the weakly domain-wall-pinned ferrimagnetic material described in Example 1 (30.2%) and At ultra-low current density (150 A / cm) 2 A schematic diagram of domain wall motion;

[0023] Figure 8 Domain walls of different configurations of the weakly domain-wall-pinned ferrimagnetic material described in Example 1 (30.2%) and At low current density (1.8 kA / cm) 2 A schematic diagram of domain wall motion. Detailed Implementation

[0024] This invention provides a weakly domain-wall-pinned ferrimagnetic material, comprising, by atomic percentage, 0-100% transition elements, 0-100% rare earth elements, and 0-100% dopant elements, wherein the sum of the transition elements, rare earth elements, and dopant elements is 100%, and the atomic percentage of the transition elements in the weakly domain-wall-pinned ferrimagnetic material is greater than the atomic percentage of the rare earth elements and dopant elements, and the atomic percentage of the rare earth elements and dopant elements in the weakly domain-wall-pinned ferrimagnetic material is not 0.

[0025] The doping elements include boron and / or nitrogen.

[0026] The weakly domain-wall-pinned ferrimagnetic material of the present invention, based on atomic percentage, comprises 0-100% transition elements, preferably 50%-60%, and more preferably 55.2%-57.6%. In the present invention, the transition elements preferably include one or more of Fe, Co, and Ni, more preferably Co. When the transition elements are two or more of the specific selections mentioned above, the present invention does not impose any special limitation on the proportions of the specific substances; they can be mixed in any proportion.

[0027] The weakly domain-wall-pinned ferrimagnetic material of the present invention, based on atomic percentage, comprises 0-100% rare earth elements, preferably 20%-40%, and more preferably 28%-31%. In the present invention, the rare earth elements preferably include one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y, and more preferably Gd. When the rare earth elements are two or more of the above-mentioned specific selections, the present invention does not impose any special limitation on the proportion of the above-mentioned specific substances; they can be mixed in any proportion.

[0028] The weakly domain-wall-pinned ferrimagnetic material of the present invention comprises 0% to 100% doping elements, preferably 10% to 20%, and more preferably 13.8% to 14.4% by atomic percentage. In the present invention, the doping elements include boron and / or nitrogen, preferably boron. When the doping elements are boron and nitrogen, the present invention does not impose any special limitation on the ratio of boron and nitrogen, and they can be mixed in any ratio.

[0029] In this invention, the transition element in the weakly domain-wall-pinned ferrimagnetic material is preferably Co, the rare earth element is preferably Gd, and the doping element is preferably B; the atomic percentage of Co in the weakly domain-wall-pinned ferrimagnetic material is preferably 10.0% to 80.0%, more preferably 50% to 70%; the atomic percentage of Gd in the weakly domain-wall-pinned ferrimagnetic material is preferably 10.0% to 80.0%, more preferably 15% to 35%; and the atomic percentage of B in the weakly domain-wall-pinned ferrimagnetic material is preferably 10.0% to 80.0%, more preferably 12% to 20%.

[0030] In this invention, the preparation method of the weak domain wall pinned subferromagnetic material is preferably physical vapor deposition, molecular beam epitaxy, chemical vapor deposition, laser pulse deposition, or laser direct writing; the physical vapor deposition is preferably evaporation coating or magnetron sputtering coating; more preferably, magnetron sputtering.

[0031] In this invention, the magnetron sputtering method preferably uses Co8B. 20 The target material and the Gd target material are co-sputtered; the background vacuum of the magnetron sputtering method is preferably 5×10⁻⁶. -8 Torr, sputtering pressure preferably 3 mTorr, sputtering temperature preferably 300 K, Co8B 20 The sputtering power is preferably 75W, and the sputtering rate is preferably 0.028nm / s; the sputtering power of Gd is variable, and when the sputtering power of Gd is 10W, the sputtering rate is 0.018nm / s (the sputtering rate increases linearly with the increase of sputtering power), and the sample rotation speed is preferably 20r / s.

[0032] The present invention does not impose any special limitations on the process of evaporation coating, molecular beam epitaxy, chemical vapor deposition, laser pulse deposition or laser direct writing, and any process known to those skilled in the art can be used.

[0033] This invention also provides the application of the weakly domain-wall-pinned subferromagnetic material described in the above-described technical solution in magnetic storage spintronic devices, magnetic logic spintronic devices, magnetic field sensors, or novel soft magnetic materials. This invention does not impose any special limitations on the methods used in these applications; methods well-known to those skilled in the art can be employed.

[0034] The following detailed description, in conjunction with embodiments, illustrates the weak domain wall pinned ferrimagnetic material and its applications provided by the present invention, but these should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] Co8B 20 target material (Co8B) 20 Co and B (with a molar ratio of 8:20) were co-sputtered with a Gd target; the background vacuum of the magnetron sputtering method was 5 × 10⁻⁶. -8 Torr, sputtering pressure 3 mTorr, sputtering temperature 300 K, Co8B 20 The sputtering power was 75 W, and the sputtering rate was 0.028 nm / s; the sputtering power of Gd was variable, and the sputtering rate of Gd was 0.018 nm / s when the sputtering power was 10 W (the sputtering rate increases linearly with the increase of sputtering power). The sample rotation speed was 20 r / s, and the resulting sample had a chemical composition of Co. 55.8 Gd 30.2 B 14.0 Weakly domain-wall-pinned ferrimagnetic materials (which can be denoted as Co) 56 Gd 30 B 14 ).

[0037] Examples 2-11 and Comparative Examples 1-2

[0038] The preparation processes of Examples 2-11 and Comparative Example 1 are the same as those in Example 1, except that the preparation conditions and parameters differ from those in Example 1, and the chemical composition of the weakly domain-wall-pinned ferrimagnetic material obtained is shown in Table 1.

[0039] Comparative Example 2 was prepared by co-sputtering with Co and Gd targets; the background vacuum of the magnetron sputtering method was 5 × 10⁻⁶. -8The sputtering pressure was 3 mTorr, the sputtering temperature was 300 K, the sputtering power of Co was 75 W, and the sputtering rate was 0.041 nm / s; the sputtering power of Gd was 23 W, and the sputtering rate was 0.041 nm / s; the sample rotation speed was 20 r / s, and the resulting sample had the chemical composition Co. 76 Gd 24 ferrimagnetic materials.

[0040] Table 1. Preparation conditions and chemical composition of Examples 2-12 and Comparative Examples 1-2

[0041]

[0042] The weakly domain-wall-pinned subferromagnetic material described in Example 1 was subjected to TEM testing, and the test results are as follows: Figure 1 As shown, where Figure 1 In the image, a is a cross-sectional high-resolution transmission electron microscope image with the multilayer structure marked; b is a Pt elemental resolution image marked in red; c is a Co elemental resolution image marked in blue; and d is a Gd elemental resolution image marked in blue.

[0043] The weak domain wall pinned ferrimagnetic material described in Example 1, amorphous Co, and Co described in Comparative Example 1 were combined. 80 B 20 And the Co described in Comparative Example 2 76 Gd 24 XAFS testing was performed, and the test results are as follows: Figure 2 As shown, where Figure 2 ad is Co 76 Gd 24 and Co 56 Gd 30 B 14 XAS values ​​of different regions in the film at the Co-K edge (a, b) and Gd-L3 edge (c, d). e and f are XAS values ​​at the Co-K edge (a, b) and Gd-L3 edge (c, d). 56 Gd 30 B 14 Co, Co 80 B 20 and Co 76 Gd 24 The radial distribution function |χ(R)| of the experimental XAFS spectrum measured at the CoK edge of the thin film. The red dashed line represents the distribution function based on CoK. 56 Gd 30 B 14 The radial distribution function obtained from the three-dimensional atomic structure, with the blue dashed line representing the distribution function based on Co. 76 Gd 24 The radial distribution function obtained from the three-dimensional atomic structure of Co. XAS of Co atoms and Co, Co 80 B 20 Co76 Gd 24 and Co 56 Gd 30 B 14 XAS comparison of amorphous thin films (b), and XAS of Gd atoms compared with those of Gd and Co. 76 Gd 24 and Co 56 Gd 30 B 14 XAS comparison of amorphous thin films (d).

[0044] Depend on Figures 1-2 It is known that the increased uniformity of the distribution of transition atoms and rare earth atoms in Co-Gd-B amorphous materials and the increased degree of amorphization reduce domain wall pinning. Furthermore, the increased number of Co-Gd atom pairs increases the antiferromagnetic coupling chain to achieve fast spin dynamics, thereby accelerating the DW motion in Co-Gd-B.

[0045] The ferrimagnetic materials described in Examples 3 (19.1%), 4 (21.6%), 5 (25.1%), 6 (28.2%), 7 (29.2%), and 1 (30.2%) were applied to a racing device. The relationship between domain wall movement velocity and magnetic field, as well as the relationship between domain wall movement velocity and current density, were measured in the racing device at 298K. The test method involved applying a long current pulse to the racing device using a Keithley 2400 source meter, or applying a long current pulse to a Helmholtz coil to generate a pulsed magnetic field. The positions of the domain walls before and after the application of the pulsed current were measured, and the movement velocity of the domain walls was calculated accordingly. The test results are as follows: Figure 3 As shown, a is a graph showing the relationship between the magnetic field-driven domain wall migration velocity and the magnetic field strength under different Gd contents; b is a graph showing the relationship between the current-driven domain wall migration velocity and the current density under different Gd contents; from Figure 3 It can be seen that in a magnetic field of 0.03 Oe or 1.8 kA / cm 2 At a current density of 10 μm / s, the domain walls can move at a speed of 10 μm / s, indicating that the material has ultra-low domain wall pinning.

[0046] The subferromagnetic material described in Example 1 was applied to a racing track device. The relationship between domain wall migration velocity and magnetic field, as well as the relationship between domain wall migration velocity and current density, were measured in the racing track device at different temperatures using the same method. The test results are as follows: Figure 4 As shown, a is a graph showing the relationship between the velocity of the magnetic domain wall driven by the magnetic field and the magnitude of the magnetic field strength at different temperatures; b is a graph showing the relationship between the velocity of the magnetic domain wall driven by the current and the magnitude of the current density at different temperatures; from Figure 4 It can be seen that as the temperature increases, the pinning strength of the domain walls decreases, and the magnetic field and current density required to drive the domain walls to move decrease.

[0047] The subferromagnetic materials described in Examples 3 (19.1%), 4 (21.6%), 6 (28.2%), 7 (29.2%), and 1 (30.2%) were applied to Hall rod devices, and the effective depilation field and density in Co-Gd-B were characterized in the Hall rod devices. Figure 5 The effective unpinning field and pinning density of the weakly domain-wall-pinned ferrimagnetic material described in Example 1 are characterized in a Hall rod device, where a represents Co, CoB, and CoFeB (Co and CoB are represented by Co and Co targets, respectively). 68 B 32 For sputtering growth of the target material at room temperature, please refer to Appl. Phys. Lett. 96, 022501 (2010); Co 60 Fe 20 B 20 Co 60 Fe 20 B 20 The target material was sputter-grown at room temperature and annealed in situ at 300°C for 2 hours (see Appl. Phys. Lett. 103, 182401 (2013) for details). The comparison of pinning site densities in the ferrimagnetic material described in Example 1 (30.2%) is shown. b represents FeTb, GdMnAs, Co, and CoFeB (the preparation of FeTb and GdMnAs is referenced in Phys. Rev. Lett. 117, 057201 (2016); the preparation of Co is referenced in Phys. Rev. Lett. 99, 217208 (2007); the preparation of CoFeB is referenced in Appl. Phys. Lett. 103, 182401 (2013)). The comparison of the effective pinning field size in CoGdB is also shown. Figure 5 It can be known that the chemical composition is Co. 56 Gd 30 B 14 The weakly domain-wall-pinned subferromagnetic material exhibits an ultra-weak effective unpinning field and an ultra-low pinning density. Figure 6 The pinning site density (a) and pinning site strength (b) of the subferromagnetic materials described in Examples 3 (19.1%), 4 (21.6%), 7 (29.2%), and 1 (30.2%) were characterized by [data missing]. Figure 6 It can be seen that the density and strength of domain wall pinning sites decrease with increasing Gd content.

[0048] Figure 7 Domain walls of different configurations of the weakly domain-wall-pinned ferrimagnetic material described in Example 1 (30.2%) and A schematic diagram of domain wall motion at ultra-low current density (current applied for 30 seconds; initial position of domain walls is indicated by green lines; scale bar: 50 μm). When the current density is as low as 150 A / cm²... 2 At that time, Co 56 Gd 30 B 14 The domain walls initially propagate along the current direction at a speed of 0.5 μm / s. Domain wall motion was measured using four configurations of domain walls in two different configurations and two different current directions to eliminate the influence of the ambient magnetic field.

[0049] Figure 8 Domain walls of different configurations of the weakly domain-wall-pinned ferrimagnetic material described in Example 1 (30.2%) and A schematic diagram of domain wall motion under low current density (the pulse current duration is 2 seconds, the initial position of the domain wall is indicated by a green line, and the scale bar is 50 μm). Figure 8 It can be seen that in Co 56 Gd 30 B 14 The current density required to excite domain wall motion (1.8 kA / cm²) 2 The current density required to excite a skyrmion with a similar velocity (approximately 15 μm / s) is more than an order of magnitude lower than that required to excite a skyrmion with a similar velocity (e.g., 35 kA / cm² in Co-Fe-B). 2 The speed is approximately 15 μm / s. See Jiang, W. et al. Science 349, 283-286 (2015).

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A weakly domain-wall-pinned subferromagnetic material, characterized in that, The weak domain wall pinned ferrimagnetic material is Co. 55.8 Gd 30.2 B 14.0 Co 66.9 Gd 16.4 B 16.7 Co 64.7 Gd 19.1 B 16.2、 Co 62.7 Gd 21.6 B 15.7 Co 59.9 Gd 25.1 B 15.0 Co 57.4 Gd 28.2 B 14.4 Co 56.6 Gd 29.2 B 14.2 Co 55.1 Gd 31.1 B 13.8 Co 54.4 Gd 32.0 B 13.6 Co 53.7 Gd 32.9 B 13.4 Co 52.8 Gd 34.0 B 13.2 or Co 52.0 Gd 35.0 B 13.0 ; The ferrimagnetic material has an amorphous structure; The weakly domain-wall-pinned subferromagnetic material is used in racing track devices.

2. The application of the weakly domain-wall-pinned subferromagnetic material of claim 1 in racing track devices.

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