A quasi-cage lattice Fe₂Ge single crystal exhibiting room-temperature anomalous Hall effect and topological Hall effect, and its growth method.

Abstract

This invention discloses a quasi-cage-like lattice Fe₂Ge single crystal exhibiting room-temperature anomalous Hall effect and topological Hall effect, and its growth method. The Fe₂Ge single crystal has a quasi-cage-like crystal structure, wherein magnetic Fe atoms are... ab The projections of the surfaces form a quasi-cage pattern. A chemical vapor deposition method is employed, using halogens or halogen compounds as transport agents, to grow the crystal within a temperature range of 750 °C to 950 °C. The grown Fe₂Ge single crystals are bulky, possess a metallic luster, and have millimeter-scale dimensions. These single crystals exhibit high-temperature ferromagnetism, with an anomalous Hall conductivity of no less than 488.50 Ω at room temperature. ‑1 · cm ‑1 The topological Hall resistivity at room temperature is not less than 0.35 μΩ·cm, which has great potential application value in spintronic devices such as room temperature anomalous Hall sensors and magnetic sensors. Furthermore, the crystal growth method disclosed in this invention has advantages such as simple growth equipment, low cost, and suitable growth temperature, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to quasi-cage-like lattice materials and crystal growth technology, specifically to a quasi-cage-like lattice Fe2Ge single crystal with room temperature anomalous Hall effect and topological Hall effect and its growth method. Background Technology

[0002] The Hall effect is a transverse electromagnetic response phenomenon arising from the Lorentz force under conditions where the magnetic field and current are perpendicular. Shortly after the discovery of the conventional (or ordinary) Hall effect, it was found that for ferromagnetic or spontaneously magnetized materials, even without an applied external magnetic field, the conductive electrons in the material still undergo transverse deflection, forming an additional Hall voltage. This transport phenomenon, independent of the conventional Lorentz force, is called the anomalous Hall effect. Furthermore, for magnetic materials with non-coplanar spin structures and non-zero scalar spin chirality, another special transverse electromagnetic response exists: the topological Hall effect. Both of these unconventional Hall effects are closely related to the material's inherent magnetism and topological states. Therefore, these unconventional Hall effects play an important role in both basic scientific research and the development of novel electronic and spintronic devices. Kagome lattice materials are a new type of quantum material. Due to their special crystal geometry, consisting of triangles sharing vertices, they are often accompanied by natural geometric frustration effects and special electronic structures such as Dirac cones, flat bands, and van Hoff singularities. Especially for quasi-clathrate magnetic materials, under the influence of magnetic order and spin-orbit coupling, they are expected to exhibit a significant intrinsic anomalous Hall effect through momentum-space Berry curvature, and a topological Hall effect due to special non-collinear or non-coplanar spin arrangements. Therefore, they are considered important candidate material systems for realizing both the anomalous and topological Hall effects. The intermetallic compound Fe₂Ge possesses a quasi-clathrate lattice, in which magnetic Fe atoms are arranged in a quasi-clathrate lattice. ab The projection of the crystal planes forms a quasi-kagome arrangement with kagome geometry characteristics, and the material has high-temperature magnetic order and potential topological electronic states, thus it is expected to exhibit many novel anomalous transport properties.

[0003] However, the preparation of Fe2Ge single crystals is challenging due to its narrow growth temperature range and the susceptibility to compositional deviations and competing phase precipitation during growth, making it difficult to obtain high-quality single-crystal samples. Therefore, current research on Fe2Ge is largely limited to basic characterization of thin film samples and polycrystalline bulk materials, while systematic transport studies have not been reported. Thus, developing a method for the stable preparation of Fe2Ge single crystals with near-stoichiometric ratios, and subsequently studying its anomalous Hall and topological Hall effects, is crucial not only for deepening our understanding of topological quantum states and novel physical effects in kabuki magnetic materials, but also for promoting their application in high-performance room-temperature spintronic devices, possessing significant scientific value and application prospects. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is, on the one hand, to provide a quasi-cage-like lattice Fe2Ge single crystal with room temperature large anomalous Hall and topological Hall effects, and on the other hand, to provide a growth method for quasi-cage-like lattice Fe2Ge single crystal based on chemical vapor transport.

[0005] Technical solution: The quasi-cage-like lattice Fe2Ge single crystal with room temperature anomalous Hall effect and topological Hall effect described in this invention is crystallized in the hexagonal crystal system, with space group [space group number missing]. P 63 / mmc In its crystal structure, magnetic Fe atoms are in ab The projection of the surface forms a quasi-cage arrangement.

[0006] Furthermore, the Fe2Ge single crystal exhibits a large room-temperature anomalous Hall effect and topological Hall effect, with an anomalous Hall conductivity of no less than 488.50 Ω at room temperature (300 K). -1 · cm -1 The topological Hall resistivity at room temperature is not less than 0.35 μΩ·cm.

[0007] Furthermore, the lattice constant of the Fe2Ge single crystal is: a=b= 4.0481(15) Å, c=5.0206(14) Å, α=β=90°, γ=120°.

[0008] Furthermore, the Fe2Ge single crystal is blocky, has a metallic luster, and is millimeter-sized, with the largest exposed surface being (00). l )noodle.

[0009] Furthermore, the Fe2Ge single crystal exhibits high-temperature ferromagnetism.

[0010] The method for growing quasi-cage lattice Fe2Ge single crystals described in this invention utilizes chemical vapor transport and includes the following steps: (1) Fe and Ge powders were used as initial raw materials and were ground and mixed evenly with the transport agent. The resulting mixture was placed in a vacuum-sealed container. (2) Place the container in a heating device, set the growth temperature program, and obtain Fe2Ge single crystals through growth.

[0011] Further, in step (1), the molar ratio of Fe to Ge is Fe:Ge = 2.0~2.2:1; the mass ratio of the initial raw material formed after mixing Fe powder and Ge powder to the transport agent is 5~15:1; the transport agent is a halogen or a halogen compound with a concentration of 3-10 mg / cm³. 3 .

[0012] Furthermore, the transport agent includes, but is not limited to, I2, Br2, or TeI4.

[0013] Further, in step (2), the heating device is a tube furnace with a horizontal dual temperature zone, and the growth temperature program is set as follows: the low temperature zone, i.e. the growth end, is 750-850 ℃, and the high temperature zone, i.e. the raw material end, is 850-950 ℃.

[0014] Furthermore, in step (2), the growth time is 10-15 days.

[0015] The quasi-cage-like lattice material described in this invention can be applied to spintronic devices. Specifically, it can be used as a high-performance room-temperature spintronic device, a magnetic sensor, and other devices. Furthermore, the proposed fabrication method can provide important insights for the design and development of the large anomalous Hall effect in other cage-like lattice materials.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) This invention grows high-quality quasi-cage-like Fe2Ge single crystals by precisely controlling the element molar ratio, using a suitable temperature gradient and the amount of transport agent through chemical vapor transport method. This solves the problems of the difficulty in preparing Fe2Ge single crystals and the difficulty in obtaining high-quality crystal samples, and provides an ideal experimental platform for further research on the rich physical properties and corresponding mechanisms of clad magnetic materials.

[0017] (2) The chemical vapor transport method for growing crystals has the advantages of high purity, good uniformity, low cost, and strong operability. It can be used as a reference for growing other quasi-cage-like quantum materials. Fe2Ge single crystal, as a new type of quasi-cage-like magnetic material, has ideal application prospects in the fields of spintronics. Attached Figure Description

[0018] Figure 1 The material characterization results of the Fe2Ge single crystal of the present invention are as follows: (a) is the crystal structure diagram of the Fe2Ge single crystal grown in Example 1; (b) is an optical photograph of the Fe2Ge single crystal grown in Example 1; (c) is the EDS pattern of the Fe2Ge single crystal grown in Example 1; and (d) is the XRD pattern of the easily dissociable surface of the Fe2Ge single crystal grown in Example 1, with all diffraction peaks being (0, 0). l The diffraction peaks on the surface.

[0019] Figure 2The electromagnetic transport results of the Fe2Ge single crystal of the present invention are shown in the figures: (a) is the magnetization curve of the Fe2Ge single crystal grown in Example 1; (b) is the Hall resistivity curve of the Fe2Ge single crystal grown in Example 1 as a function of temperature, with an inset showing a schematic diagram of the testing device; (c) is the anomalous Hall resistivity curve of the Fe2Ge single crystal grown in Example 1 as a function of temperature, with an inset showing the anomalous Hall conductivity curve of the Fe2Ge single crystal as a function of temperature; and (d) is the topological Hall resistivity curve of the Fe2Ge single crystal grown in Example 1 as a function of temperature.

[0020] Figure 3 The electromagnetic transport results of the Fe2Ge single crystal grown in Example 1 of this invention are shown in another direction. (a) is the magnetization curve of the Fe2Ge single crystal; (b) is the Hall resistivity curve of the Fe2Ge single crystal as a function of temperature, and the inset is a schematic diagram of the test device; (c) is the anomalous Hall resistivity curve of the Fe2Ge single crystal as a function of temperature; and (d) is the topological Hall resistivity curve of the Fe2Ge single crystal as a function of temperature.

[0021] Figure 4 For the structural characterization of Example 2, (a) is the energy dispersive X-ray spectrum (EDS); (b) is the XRD pattern.

[0022] Figure 5 The electromagnetic transport results of the Fe2Ge single crystal grown in Example 2 of the present invention are shown in (a) and (b) respectively. (c) shows the magnetization curve of the Fe2Ge single crystal; (d) shows the Hall resistivity curve of the Fe2Ge single crystal as a function of temperature. The inset is a schematic diagram of the test device. (c) shows the anomalous Hall resistivity curve of the Fe2Ge single crystal as a function of temperature; (d) shows the topological Hall resistivity curve of the Fe2Ge single crystal as a function of temperature. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by known methods.

[0024] In the experiments of this invention embodiment, high-purity Fe and Ge powders were used as raw materials, and the transport agent I2 used was also a high-purity reagent. The quartz tube for growing crystals was made of high-purity quartz.

[0025] Example 1: The quasi-cage lattice Fe2Ge single crystal provided in this example is prepared by the following method: First, using an electronic balance, weigh out 1g of Fe powder and Ge powder according to the Fe:Ge molar ratio of 2.2:1, and add approximately 100mg of transport agent I2 at a concentration of 3 mg / cm³. 3After grinding and mixing the two materials evenly, the mixture is placed into a pre-prepared quartz tube (10 cm in length and 2 cm in diameter). The quartz tube is then sealed and placed in a two-zone tube furnace. The growth temperature program is set from 750 ℃ ​​(low-temperature end) to 850 ℃ (raw material end). After a growth cycle of approximately 10 days, natural cooling yields millimeter-sized, high-quality Fe2Ge single crystals, with a maximum size of approximately 2 mm. Figure 1 As shown in (b).

[0026] like Figure 1 As shown in (a), this Fe2Ge single crystal... ab The crystal faces exhibit a quasi-kagamine arrangement with kagamine geometry. Its energy-dispersive X-ray spectrum (EDS) is as follows: Figure 1 As shown in (c), the results indicate that the single crystal is composed of Fe and Ge elements, with no impurities. Quantitative calculations show that the ratio of the two elements is close to the stoichiometry. The XRD pattern is shown below. Figure 1 As shown in (d), X-ray diffraction (XRD) analysis indicates that all diffraction peaks of the prepared single crystal are (00...). l The peak indicates that the sample is along the [path]. ab Surface growth.

[0027] Simultaneously, the physical properties of the grown Fe2Ge single crystals were characterized, and the results are as follows: Figure 2 As shown, the magnetization intensity curve is as follows Figure 2 As shown in (a); the change of Hall resistivity with temperature is as follows Figure 2 As shown in (b); the curves of anomalous Hall resistivity and anomalous Hall conductivity as a function of temperature are as follows. Figure 2 As shown in (c); it exhibits a significant anomalous Hall effect: the anomalous Hall conductivity at room temperature is approximately 488.50 Ω. -1 · cm -1 The curves showing the change in topological Hall resistivity with temperature are as follows: Figure 2 As shown in (d), it exhibits a significant topological Hall effect with a topological Hall resistivity of 0.35 μΩ·cm at room temperature.

[0028] Next, the anisotropic physical properties of the Fe2Ge single crystal from Example 1 were characterized, and the results are as follows: Figure 3 As shown, the magnetization intensity curve is as follows Figure 3 As shown in (a); the change of Hall resistivity with temperature is as follows Figure 3 As shown in (b); the curves of anomalous Hall resistivity and topological Hall resistivity as a function of temperature are as follows. Figure 3 As shown in (c) and 3(d), they also exhibit significant anomalous Hall effect and topological Hall effect.

[0029] Example 2: First, using Fe and Ge powder as initial raw materials, according to the molar ratio of Fe:Ge = 2.0:1, a total of 1.5 g of Fe powder and Ge powder were weighed using an electronic balance, along with approximately 200 mg of transport agent I2 at a concentration of 10 mg / cm³. 3 After grinding and mixing the two materials evenly, the mixture is placed into a pre-prepared quartz tube. The quartz tube is then sealed and placed in a two-zone tube furnace (10cm long, 2cm in diameter). The growth temperature program is set from 850℃ (low-temperature end) to 950℃ (raw material end). After a growth cycle of approximately 15 days, natural cooling yields millimeter-sized, high-quality Fe2Ge single crystals, with a maximum size of approximately 1.5 mm. Figure 4 As shown in the illustration in (a).

[0030] The relevant characterization results are as follows Figure 4 As shown, energy-dispersive X-ray spectroscopy (EDS) is as follows: Figure 4 As shown in (a), the results indicate that the single crystal is composed of Fe and Ge elements, with no impurities. Quantitative calculations show that the ratio of the two elements is close to the stoichiometry. The XRD pattern is shown below. Figure 4 As shown in (b), X-ray diffraction (XRD) analysis indicates that all diffraction peaks of the prepared single crystal are (00...). l The peak indicates that the sample is along the [path]. ab Surface growth.

[0031] Meanwhile, the Fe2Ge single crystals grown in Example 2 were characterized for their physical properties, and the results are as follows: Figure 5 As shown, the magnetization intensity curve is as follows Figure 5 As shown in (a); the change of Hall resistivity with temperature is as follows Figure 5 As shown in (b); the curves of anomalous Hall resistivity and topological Hall resistivity as a function of temperature are as follows. Figure 5 As shown in (c) and 5(d), they also exhibit significant anomalous Hall effect and topological Hall effect.

Claims

1. A quasi-cage-like lattice Fe₂Ge single crystal exhibiting room-temperature anomalous Hall effect and topological Hall effect, characterized in that, The Fe₂Ge crystallizes in a hexagonal crystal system with space group [space group missing]. P 63 / mmc In its crystal structure, magnetic Fe atoms are in ab The projection of the surface forms a quasi-cage arrangement.

2. The Fe₂Ge single crystal according to claim 1, characterized in that, The Fe2Ge single crystal exhibits a large room-temperature anomalous Hall effect and topological Hall effect, with an anomalous Hall conductivity of no less than 488.50 Ω at room temperature. -1 · cm -1 The topological Hall resistivity at room temperature is not less than 0.35 μΩ·cm.

3. The Fe₂Ge single crystal according to claim 1, characterized in that, The lattice constant of the Fe2Ge single crystal is: a=b= 4.0481(15) Å, c=5.0206(14) Å, α = β =90°, γ =120°.

4. The Fe₂Ge single crystal according to claim 1, characterized in that, The Fe2Ge single crystal is in bulk form, has a metallic luster, and is millimeter-sized; the Fe2Ge single crystal exhibits high-temperature ferromagnetism.

5. A method for growing a quasi-cage-like lattice Fe₂Ge single crystal with room-temperature anomalous Hall effect and topological Hall effect as described in any one of claims 1-4, characterized in that, The method is a chemical vapor transport method, which includes the following steps: (1) Fe powder and Ge powder are used as initial raw materials, and are ground and mixed evenly with the transport agent. The resulting mixture is placed in a vacuum-sealed quartz tube container. (2) Place the container in a heating device, set the growth temperature program, and obtain Fe2Ge single crystals through growth.

6. The growth method according to claim 5, characterized in that, In step (1), the molar ratio of Fe powder to Ge powder is Fe:Ge = 2.0-2.2:1; the mass ratio of the initial raw material formed after mixing Fe powder and Ge powder to the transporter is 5-15:1; the transporter is a halogen or halogen compound, with a concentration of 3-10 mg / cm³ based on the effective volume of the quartz tube. 3 .

7. The growth method according to claim 6, characterized in that, The transport agent includes I2, Br2 or TeI4.

8. The growth method according to claim 5, characterized in that, In step (2), the heating device is a tube furnace with a horizontal dual temperature zone, and the growth temperature program is set as follows: the low temperature zone, i.e. the growth end, is 750-850 ℃, and the high temperature zone, i.e. the raw material end, is 850-950 ℃.

9. The growth method according to claim 5, characterized in that, In step (2), the growth time is 10-15 days.

10. The application of the quasi-cage-like lattice Fe2Ge single crystal with room-temperature anomalous Hall effect and topological Hall effect as described in claim 1 in high-performance room-temperature spintronic devices.

Images