Magnetic Weel semimetal crystal with huge abnormal Hall angle and implementation strategy thereof

Abstract

The invention discloses a magnetic Weel semimetal crystal with a huge abnormal Hall angle and an implementation strategy of the magnetic Weel semimetal crystal, and the chemical formula of the crystal is Co3Sn2 (S1-xSex) 2, 0lt, xlt; and 0.1. The strategy for realizing the huge abnormal Hall angle is a magnetic microstructure project: spin-orbit coupling is increased, Dzyaloshiski-Moriya interaction is enhanced, and a magnetic structure similar to the skyrmion is induced in Co3Sn2 (S1-xSex) 2, so that the abnormal Hall effect is remarkably enhanced; and meanwhile, the abnormal Hall effect in the magnetic Weel semimetal crystal can be regulated and controlled by controlling chemical components, the grown magnetic Weel semimetal crystal has an abnormal Hall angle up to 42%, and the magnetic Weel semimetal crystal has huge potential application value in the aspect of spintronics devices. In addition, in the implementation strategy, crystal growth adopts a chemical vapor transport method, growth equipment is simple, the cost is low, and the method can be used for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of Weyl semimetal materials and crystal growth, and in particular to a magnetic Weyl semimetal crystal with a huge anomalous Hall angle and a realization strategy thereof. Background Art

[0002] The phenomenon that carriers of metal conductors and semiconductors that are energized in a magnetic field generate a transverse potential difference due to the Lorentz force is called the Hall effect. In ferromagnetic materials, a transverse potential difference can still be generated even without a magnetic field. This phenomenon is called the anomalous Hall effect. The anomalous Hall effect generally includes two microscopic mechanisms. One is the extrinsic mechanism related to the asymmetric scattering of carriers by impurities; the other is related to the Bailey curvature of the material, which is called the intrinsic mechanism. Usually, the magnitude of the anomalous Hall effect is jointly regulated by the intrinsic / extrinsic mechanisms. As an important parameter to measure the magnitude of the anomalous Hall effect, the anomalous Hall angle, that is, the ratio of the transverse Hall conductance to the longitudinal conductance, reflects the efficiency of the longitudinal drive current that can be converted into the transverse Hall current. The huge anomalous Hall angle is of guiding significance for understanding quantum physics phenomena and designing new electronic devices. It can provide a stable operating platform for quantum bits and help develop more reliable quantum computing technology.

[0003] As a pseudomagnetic field in momentum space, the Berry curvature originates from the inter-band interaction of Bloch electrons. The intrinsic anomalous Hall conductivity generated is more resistant to the destruction of defects and thermal disturbances, has higher stability, and is more conducive to device applications. In recent years, some magnetic topological materials have shown huge anomalous Hall effects and large anomalous Hall angles due to the topologically enhanced Berry curvature, such as Co2MnGa / A1 (abnormal Hall angle of about 12%), Co3Sn2S2 (abnormal Hall angle of about 20%), etc., which are much larger than many traditional magnetic materials. Among them, Co3Sn2S2 is a member of the Shandite compound family. In the prior art, its linearly dispersed band structure and the topological surface state Fermi arc connecting the Weyl nodes were directly observed by angle-resolved photoelectron spectroscopy technology, and it was experimentally proved that Co3Sn2S2 is the first magnetic Weyl semimetal discovered. Since there are three pairs of Weyl points with opposite chirality and open nodal line loops near its Fermi surface, it exhibits a strong Bailey curvature distribution near the Fermi level, which makes this material exhibit a significant anomalous Hall effect. At present, many scholars have achieved the regulation of the anomalous Hall effect by doping Co3Sn2S2 with elements such as Fe and Ni, thereby introducing the contribution of extrinsic impurity scattering on the basis of the intrinsic anomalous Hall effect, and improving its anomalous Hall angle.

[0004] Practical applications and device designs based on the anomalous Hall effect often need to meet different requirements, which requires the anomalous Hall effect material to have a larger Hall angle and continuously adjustable physical properties. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a magnetic Weyl semimetal crystal with a large anomalous Hall angle that can achieve tunable magnetic microstructures. Another object of the present invention is to provide an implementation strategy for the above crystal based on the chemical vapor transport method under the action of a temperature field, and to prepare high-quality magnetic Weyl semimetal crystals by regulating the temperature gradient and the dosage of the transport agent.

[0006] Technical Solution: In the magnetic Weyl semimetal crystal with a large anomalous Hall angle of the present invention, Se element with stronger spin-orbit coupling is doped in the magnetic Weyl semimetal Co3Sn2S2, thereby breaking the center inversion symmetry, introducing the Dzyaloshinskii-Moriya interaction, and generating spin texture.

[0007] Further, the chemical formula of the crystal is Co3Sn2(S 1-x Se x )2, where 0 < x < 0.1, preferably 0.01 < x < 0.06, and more preferably 0.025 < x < 0.045.

[0008] Further, the shape of the crystal is hexagonal, the size is millimeter-level, and the crystal has a metallic luster.

[0009] Further, the crystal has a magnetic structure similar to a "elliptical" skyrmion, and these magnetic structures can significantly enhance the anomalous Hall effect in the material.

[0010] Further, the anomalous Hall angle of the crystal is 32% - 42% at 130K.

[0011] Preferably, the anomalous Hall angle of the crystal Co3Sn2Se 1.91 S 0.09 is 42% at 130K, and nearly half of the longitudinal current can be converted into a transverse current.

[0012] The implementation strategy of the above magnetic Weyl semimetal crystal with a large anomalous Hall angle uses the chemical vapor transport method under the action of a temperature field, and includes the following steps:

[0013] (1) Using Co, Sn, S, and Se powders as starting materials, weighing them according to the molar ratio of Co:Sn:S:Se = 3:2:2 - y:y, 2x < y, 0 < x < 0.1, and performing a solid-phase sintering reaction in a closed vacuum environment to synthesize polycrystalline Co3Sn2S 2-y Se y powder;

[0014] (2) Placing the above polycrystalline Co3Sn2S 2-y Sey The powder and the transport agent are ground and mixed uniformly, and the resulting mixture is placed in a vacuum sealed container;

[0015] (3) Place the above container in a heating device, set the growth temperature program, and obtain Co3Sn2(S 1- x Se x )2Single crystal.

[0016] Furthermore, in step (1), the conditions of the solid phase sintering reaction are: reaction temperature is 850-950° C., and reaction time is 5-7 days.

[0017] Furthermore, in step (2), the polycrystalline Co3Sn2S 2-y Se y The mass ratio of powder to transport agent is 1-1.5:100-150, and the transport agent is I2 with a concentration of about 5-10 mg / cm 3 .

[0018] Furthermore, in step (2), the vacuum sealed container is a quartz tube with a length of 10-20 cm and a diameter of 1-2 cm.

[0019] Furthermore, in step (3), the heating device is a tubular furnace with horizontal dual temperature zones, and the growth temperature program is set as: 820-900°C in the upper temperature zone and 900-1000°C in the lower temperature zone, i.e., the raw material end.

[0020] Furthermore, in step (3), the growth time is 7-15 days.

[0021] The magnetic Weyl semimetal crystal material can be applied to spin electronics devices. Specifically, it can be used as a magnetic sensor, magnetic random access memory, spin transfer torque and other devices. At the same time, the proposed preparation method can also be used to provide important reference for the design and development of the large anomalous Hall effect of other magnetic topological materials.

[0022] The present invention adopts a suitable transport agent and grows a high-quality new magnetic Weyl semimetal Co3Sn2(S 1-x Se x )2 crystals provide an ideal experimental platform for further studying the rich physical properties and corresponding mechanisms of the Shandite series of materials. The chemical vapor transport method for growing crystals has the advantages of high purity, high quality, low cost, and strong operability, which can be used as a reference for growing crystals of other topological Weyl semimetal materials. More importantly, Co3Sn2(S 1-x Se x)2 crystal, as a new type of magnetic Weyl semimetal material, has ideal application prospects in fields such as spin electronics.

[0023] Principle of the invention: The present invention introduces Se elements with stronger spin-orbit coupling into Co3Sn2S2 to replace S to enhance the Dzyaloshinskii-Moriya interaction. 1-x Se x )2 crystals produce an "elliptical" spin magnetic structure similar to that of skyrmions. These inhomogeneous magnetic structures can significantly enhance the 1-x Se x )2 crystals. Therefore, the present invention provides a new strategy, namely magnetic microstructure engineering, which can significantly improve the anomalous Hall effect of compounds, making the magnetic Weyl semimetal Co3Sn2(S)2 crystals have a higher temperature and a higher anomalous Hall effect. 1- x Se x )2 has an anomalous Hall angle of up to 42% and is adjustable under component induction. The new magnetic Weyl semimetal crystal Co3Sn2(S 1-x Se x )2 It will help to develop new spin electronic devices with low power consumption, high speed, small size and low information loss, and promote the potential application of emerging magnetic topological materials in topological spin electronics, magnetic sensing, electrothermal energy conversion, etc.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) Co3Sn2(S 1-x Se x )2 crystal material, successfully in Co3Sn2(S 1-x Se x )2 crystals produce an "elliptical" spin magnetic structure similar to skyrmions, obtain a larger anomalous Hall angle (up to 42%), and achieve a huge anomalous Hall effect; (2) the present invention proposes a new strategy - magnetic microstructure engineering, to significantly enhance the physical properties of quantum materials; (3) the preparation method provides a temperature field-based chemical vapor transport growth Co3Sn2 (S 1-x Se x )2 crystal method has the advantages of simple device, easy operation, low cost, and can effectively realize the simultaneous doping of multiple elements; (4) The Co3Sn2 (S 1-x Se x)2 crystal is a new type of magnetic Weyl semimetal material, which can be used as an ideal system to realize the regulation of the anomalous Hall effect of the material. This is of great significance for studying how to effectively improve the anomalous Hall effect of Co3Sn2S2-based doped materials in order to develop related devices. It can also provide important reference for the design and development of large anomalous Hall effect of other magnetic topological materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Co3Sn2S prepared in Example 1 1.91 Se 0.09 XRD pattern of the crystal, the inset in the upper right corner of the figure is an optical photograph;

[0026] Figure 2 Co3Sn2S prepared in Example 1 1.91 Se 0.09 EDS spectrum of the crystal;

[0027] Figure 3 Co3Sn2S prepared in Example 1 1.91 Se 0.09 Magnetic force microscopy image of the crystal;

[0028] Figure 4 Co3Sn2S prepared in Example 1 1.91 Se 0.09 Temperature dependence of the crystal's anomalous Hall angle diagram;

[0029] Figure 5 This is the XRD pattern of the Co3Sn2S2 crystal prepared in Comparative Example 1, and the inset in the upper right corner of the figure is an optical photograph;

[0030] Figure 6 This is a magnetic force microscope image of the Co3Sn2S2 crystal prepared in Comparative Example 1;

[0031] Figure 7 is a temperature-dependent anomalous Hall angle diagram of the Co3Sn2S2 crystal prepared in Comparative Example 1;

[0032] Figure 8 Co3Sn2S prepared in Example 2 1.95 Se 0.05 XRD pattern of the crystal, the inset in the upper right corner of the figure is an optical photograph;

[0033] Fig. 9 Co3Sn2S prepared in Example 2 1.95 Se 0.05 Magnetic force microscopy image of the crystal;

[0034] Fig.10 Co3Sn2S prepared in Example 2 1.95 Se0.05 Temperature dependence of the anomalous Hall angle of the crystal. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments and drawings.

[0036] In the experiments of the embodiments of the present invention, high-purity powders such as (Co, Sn, S and Se) are used as raw materials, the transport agent I2 used is also a high-purity reagent, and the quartz tube for growing the crystal is made of high-purity quartz.

[0037] Example 1: The chemical formula of the magnetic Weyl semimetal crystal provided in this example is: Co3Sn2S 1.91 Se 0.09 , the preparation method is as follows:

[0038] 0.09 mol of Co powder (5.304 g), 0.06 mol of Sn powder (7.123 g), 0.057 mol of S powder (1.823 g) and 0.003 mol of Se powder (0.237 g) were weighed, mixed evenly and loaded into a pre-prepared quartz tube, which was sealed under vacuum with a mechanical pump and a molecular pump, and subjected to high-temperature solid-phase sintering reaction at 900 °C for 5 days to prepare Co3Sn2S 1.9 Se 0.1 Then weigh about 1.0g of Co3Sn2S 1.9 Se 0.1 Powder with about 110mg of transport agent I2, concentration of 5mg / cm 3 , grind and mix the two evenly and put them into a pre-prepared quartz tube (length 10cm, diameter 2cm). After the quartz tube is sealed, it is placed in a two-temperature zone tube furnace, and the growth temperature program is set to 825℃ (low temperature end) ~ 925℃ (raw material end). After a growth cycle of about 10 days, the temperature is naturally lowered to obtain millimeter-level high-quality Co3Sn2S 1.91 Se 0.09 Large single crystals, up to about 4 mm in size, such as Figure 1 As shown in the illustration in the upper right corner of the figure.

[0039] XRD pattern Figure 1 As shown, X-ray diffraction (XRD) analysis shows that all diffraction peaks of the crystal prepared above are (001) peaks, indicating that the sample grows along the ab plane. Figure 2 As shown, EDS test shows that the actual composition of the above crystal is Co3Sn2S 1.91 Se 0.09 , and the composition is evenly distributed. Magnetic tests show that Co3Sn2S 1.91 Se 0.09The crystal exhibits an "elliptical" magnetic structure ( Figure 3 ) is completely different from the ferromagnetic domains exhibited by Co3Sn2S2. Figure 4 Co3Sn2S 1.91 Se 0.09 The temperature-dependent anomalous Hall angle of the crystal shows that the anomalous Hall angle of the crystal prepared by the above method is significantly improved, especially in the high temperature region, up to 42% at 130K.

[0040] Comparative Example 1: The chemical formula of the magnetic Weyl semimetal crystal provided in this comparative example is: Co3Sn2S2, and the preparation method is as follows:

[0041] Weigh 0.09 mol of Co powder (5.304 g), 0.06 mol of Sn powder (7.123 g), and 0.06 mol of S powder (1.9239 g), mix them evenly, and put them into a pre-prepared quartz tube. Seal it under vacuum with a mechanical pump and a molecular pump, and perform high-temperature solid-phase sintering reaction at 900 ° C for 5 days to prepare Co3Sn2S2 powder as the growth raw material. Then weigh about 1.0 g of Co3Sn2S2 powder and about 120 mg of transport agent I2, with a concentration of 5 mg / cm 3 , grind and mix the two evenly and put them into a pre-prepared quartz tube (length 10cm, diameter 2cm). After the quartz tube is sealed, it is placed in a two-temperature zone tube furnace, and the growth temperature program is set to 825℃ (low temperature end / crystal growth section) ~ 925℃ (raw material end). After a growth cycle of about 10 days, the temperature is naturally lowered to obtain a millimeter-level high-quality Co3Sn2S2 large single crystal with a size of about 3mm. Figure 5 As shown in the illustration in the upper right corner of the figure.

[0042] like Figure 5 As shown, X-ray diffraction test (XRD) analysis shows that all diffraction peaks of the Co3Sn2S2 crystal prepared above are (00l) peaks, indicating that the sample grows along the ab plane. Figure 6 The magnetic structure of the Co3Sn2S2 crystal can be seen in the comparative example that the magnetic structure of the undoped crystal is a ferromagnetic domain, such as Figure 7 is the temperature-dependent anomalous Hall angle in Co3Sn2S2 crystal. The anomalous Hall angle is lower than that of Co3Sn2S 1.91 Se 0.09 Crystals have been demonstrated to be able to control the magnetic domain structure of magnetic Weyl semimetals and achieve the control of the anomalous Hall angle.

[0043] Example 2: The chemical formula of the magnetic Weyl semimetal crystal provided in this example is: Co3Sn2S 1.95 Se 0.05 , the preparation method is as follows:

[0044] 0.09 mol of Co powder (5.304 g), 0.06 mol of Sn powder (7.123 g), 0.0582 mol of S powder (1.866 g) and 0.0018 mol of Se powder (0.142 g) were weighed, mixed evenly and loaded into a pre-prepared quartz tube, which was sealed under vacuum with a mechanical pump and a molecular pump, and subjected to high-temperature solid-phase sintering reaction at 900 °C for 5 days to prepare Co3Sn2S 1.94 Se 0.06 Then weigh about 1.0g of Co3Sn2S 1.94 Se 0.06 Powder with about 120mg of transport agent I2, concentration of 5mg / cm 3 , grind and mix the two evenly and put them into a pre-prepared quartz tube (length 10cm, diameter 2cm). After the quartz tube is sealed, it is placed in a two-temperature zone tube furnace, and the growth temperature program is set to 825℃ (low temperature end / crystal growth section) ~ 925℃ (raw material end). After a growth cycle of about 10 days, the temperature is naturally lowered to obtain millimeter-level high-quality Co3Sn2S 1.95 Se 0.05 Large single crystals, up to about 3 mm in size, such as Figure 7 As shown in the illustration in the upper right corner of the figure.

[0045] like Figure 8 As shown, X-ray diffraction (XRD) analysis shows that the Co3Sn2S 1.95 Se 0.05 All diffraction peaks of the crystal are (00l) peaks, indicating that the sample grows along the ab plane. Fig. 9 Co3Sn2S 1.95 Se 0.05 The magnetic structure of the crystal, it can be seen that the magnetic structure of the crystal in this embodiment is an "elliptical" magnetic structure, but the magnetic domain density is different from that in embodiment 1, such as Fig.10 Co3Sn2S 1.95 Se 0.05 The temperature-dependent anomalous Hall angle in the crystal shows that the anomalous Hall angle of the crystal in this embodiment is 32%, which proves that the inventive technology can achieve the regulation of the anomalous Hall angle.

Claims

1. A magnetic Weyl semimetal crystal with a huge anomalous Hall angle, characterized in that: By doping Se elements with stronger spin-orbit coupling into the magnetic Weyl semimetal Co3Sn2S2, the central inversion symmetry is broken, the Dzyaloshinskii-Moriya interaction is introduced, and spin texture is generated.

2. The magnetic Weyl semimetal crystal according to claim 1, characterized in that: The chemical formula of the crystal is Co3Sn2(S 1-x Se x )2, where 0 <x<0.1。 3. The magnetic Weyl semimetal crystal according to claim 2, characterized in that: The crystal is hexagonal in shape, millimeter-sized, and has a metallic luster.

4. The magnetic Weyl semimetal crystal according to claim 2, characterized in that: The crystal has an "elliptical" magnetic structure similar to that of skyrmions.

5. The magnetic Weyl semimetal crystal according to claim 2, characterized in that: The anomalous Hall angle of the crystal at 130K is 32%-42%.

6. A strategy for realizing the magnetic Weyl semimetal crystal with a giant anomalous Hall angle as claimed in any one of claims 1 to 5, characterized in that: The chemical vapor transport method using the temperature field effect includes the following steps: (1) Using Co, Sn, S, and Se powders as the starting materials,配料 according to the molar ratio of Co:Sn:S:Se = 3:2:2 - y:y, 2x < y, 0 < x < 0.1, and performing solid-phase sintering reaction in a sealed vacuum environment to synthesize polycrystalline Co3Sn2S 2-y Se y powder; (2) The above polycrystalline Co3Sn2S 2-y Se y The powder and the transport agent are ground and mixed uniformly, and the resulting mixture is placed in a vacuum sealed container; (3) Place the above container in a heating device, set the growth temperature program, and obtain Co3Sn2(S 1-x Se x )2Single crystal.

7. The implementation strategy according to claim 6, characterized in that: In step (1), the conditions of the solid phase sintering reaction are: reaction temperature is 850-950° C., and reaction time is 5-7 days.

8. The implementation strategy according to claim 6, characterized in that: In step (2), the polycrystalline Co3Sn2S 2-y Se y The mass ratio of powder to transport agent is 1-1.5:100-150, and the transport agent is I2 with a concentration of about 5-10 mg / cm 3 .

9. The implementation strategy according to claim 6, characterized in that: In step (3), the heating device is a tubular furnace with horizontal dual temperature zones, and the growth temperature program is set as follows: 820-900°C in the upper temperature zone (growth end) and 900-1000°C in the lower temperature zone, i.e., the raw material end.

10. The implementation strategy according to claim 6, characterized in that: In step (3), the growth time is 7-15 days.

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