A single crystal of EuSb2, an antiferromagnetic topological half-metal material, and its preparation method.

Abstract

The application relates to an antiferromagnetic topological semimetal material EuSb2 single crystal and a preparation method thereof, and belongs to the technical field of single crystal materials. The cell parameters of the single crystal are as follows: a=4.7680 A, b=4.2990 A, c=8.97 A, alpha=gamma=90 DEG, beta=103.01 DEG. A flux method is adopted, and Tl-Sn is selected as a flux, and the addition of Tl and Sn elements helps the faster and more uniform fusion of Eu and Sb elements in the single crystal, so that better nucleation crystallization is achieved. The material is an antiferromagnetic material, and the Niel temperature of magnetic transition is 22.3K.

Description

Technical Field

[0001] This invention relates to a single crystal of EuSb2, an antiferromagnetic topological half-metal material, and its preparation method, belonging to the field of single crystal material technology. Background Technology

[0002] In topological nodal half-metals, Dirac or Weyl half-metals, these gapless points in momentum space give rise to many novel quantum transport phenomena. Theoretical predictions indicate that the topological properties of topological nodal half-metals manifest in the quantum oscillations of bulk and surface states. Therefore, the fabrication of high-mobility thin films or single crystals is particularly important. On the other hand, when spin-orbit coupling is considered, many ordinary nodal materials transform into topological insulators or nodal half-metals. Therefore, non-point-symmetric crystal structures are necessary. CaSb2 is a novel topological nodal half-metal material, and EuSb2, with the same structure, is expected to have a large magnetic moment based on this unique crystal structure. Although polycrystalline antiferromagnetic order was reported for this material in the 1980s, and its transport properties have been studied in single-crystal thin films in recent years, the test results may be affected by defects in polycrystalline and thin films, and the fact that thin films are grown on substrates. Therefore, to comprehensively explore the intrinsic physical properties of the material, it is essential to grow single-crystal bulk materials. Only by obtaining single-crystal bulk material samples can subsequent quantum devices and future applications based on magnetic topological materials be promoted. There are currently no reports on EuSb2 single crystals and their preparation methods. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an antiferromagnetic topological half-metal material EuSb2 single crystal and its preparation method.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows.

[0005] A single crystal of EuSb2, an antiferromagnetic topological half-metal material, has the following cell parameters: a=4.7680 Å, b=4.2990 Å, c=8.97 Å, α=γ=90°, β=103.01°.

[0006] A method for preparing EuSb2 single crystal, an antiferromagnetic material according to the present invention, employs a fluxing method using a Tl-Sn binary compound as a fluxing agent. The method includes the following steps: (1) According to the stoichiometric ratio of EuSb2 to Tl-Sn of 1:10~1:40, weigh the raw materials Eu blocks, Tl particles, Sb particles and Sn particles respectively in an environment where the water and oxygen content are both less than 0.1 ppm, put them into a crucible, put the crucible into a quartz tube, and vacuum seal the quartz tube. The purity of the raw material is greater than or equal to 99.999%; The vacuum degree of the vacuum seal is 1×10⁻⁶. -4 Pa or above; (2) Place the quartz tube after vacuum sealing in step (1) into a muffle furnace for firing. The furnace program is set as follows: first, heat the quartz tube from room temperature to 900~1100℃, keep it at a constant temperature for more than 24 hours, then cool it down to 400~600℃, then open the furnace door, invert the quartz tube and put it into a centrifuge to remove excess products except for single crystals. (3) Open the quartz tube and pick out the single crystal. Some single crystals are stuck together due to the flux. You need to use a blade to cut them along the crystal direction of the single crystal growth to obtain independent single crystals and obtain a single crystal of an antiferromagnetic topological half-metal material EuSb2.

[0007] Preferably, in step (1), the raw materials Eu blocks, Tl particles, Sb particles and Sn particles are respectively loaded into a quartz tube, and then purged with argon in a vacuum sealing system. Finally, hydrogen gas at a pressure of more than 0.8 atmospheres is introduced into the quartz tube to seal the hydrogen gas inside the quartz tube. The above raw materials are annealed at a temperature 50°C lower than their respective melting points to remove the oxide layer on the surface.

[0008] Preferably, in step (1), the vacuum degree of the vacuum seal is 3×10⁻⁶. -4 Pa~5×10 -4 Pa.

[0009] Preferably, in step (1), the weighing error of the raw materials is less than or equal to 0.01%.

[0010] Preferably, in step (2), the quartz tube after vacuum sealing in step (1) is placed in a muffle furnace for firing. The program is set as follows: first, the temperature is raised from room temperature to 900-1100℃ in 9-11 hours, and then kept at a constant temperature for more than 24 hours. Then, the temperature is lowered to 400-600℃ at a rate of 1-4℃ / h. The furnace door is then opened, and the quartz tube is placed upside down in a centrifuge to remove excess products other than single crystals. During the centrifugation process, the quartz tube needs to be taken out of the furnace quickly, otherwise the single crystals will solidify in the flux.

[0011] Beneficial effects This invention provides a single crystal of EuSb2, an antiferromagnetic topological half-metal material. Magnetoresistance results indicate that the single crystal is a topological half-metal. This single crystal is beneficial for subsequent quantum devices and future applications based on magnetic topological materials.

[0012] This invention provides a method for preparing single crystals of the antiferromagnetic topological half-metal material EuSb2, employing a flux method. Tl-Sn is selected as the flux. Tl and Sn elements have low melting points; when these two elements form a binary compound in a certain proportion, the melting point is even lower, which helps the two elements in the single crystal fuse together more quickly and uniformly, thus promoting better nucleation and crystallization. The ratio of the parent phase EuSb2 to the flux in this invention was determined after trying many other ratios. The selection of the centrifugation temperature involved in this invention is crucial. When the temperature exceeds 600℃, the single crystal will be centrifuged away along with the flux, while below 400℃, the flux and the single crystal bond together, resulting in a small number of single crystals with low quality. Attached Figure Description

[0013] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the single crystal described in Example 1.

[0014] Figure 2 The images shown are scanning electron microscope (SEM) images (a) and corresponding energy dispersive spectroscopy (EDS) spectra (b) of the single crystal described in Example 1.

[0015] Figure 3 The image shows the magnetic properties of the single crystal described in Example 1. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments.

[0017] Example 1 (1) According to the stoichiometric ratio of parent phase EuSb2: flux Tl-Sn=1:20, weigh the raw materials respectively in an environment where the water and oxygen content are both less than 0.1ppm. The raw materials are 0.5334g of Eu block, 0.2870g of Tl particles, 0.5128g of Sb particles and 1.6668g of Sn particles. Put them into a crucible with a diameter of 1cm. After weighing, put the crucible into a quartz tube and vacuum seal the quartz tube. The raw materials are Sn, Eu, and Sb, and the purity of the raw materials is not less than 99.999%. Since raw materials Tl and Sb are easily oxidized in air, in order to improve the electrical performance of the prepared single crystal, it is preferable to encapsulate each raw material in a quartz tube filled with hydrogen at 0.8 atmospheres and anneal them at a temperature 50°C below their melting point to remove the oxide layer on the surface. Preferably, the vacuum degree of the vacuum seal is 4×10⁻⁶. -4 Pa; Preferably, the weighing error of the raw materials is 0.01%; (2) Place the quartz tube after vacuum sealing in step (1) into a muffle furnace for firing. The furnace program is set as follows: heat up to 1000℃ from room temperature in 10 hours, keep the temperature constant for 24 hours, and then cool down to 400℃ at a rate of 3.5℃ / h. Then open the furnace door, invert the quartz tube and place it in a centrifuge to remove excess products except for single crystals. (3) Open the quartz tube and pick out the single crystal.

[0018] The single crystals prepared in this invention are strip-shaped, plate-shaped, and have a metallic luster. First, the single crystal samples were characterized by XRD, and the results are as follows... Figure 1 As shown, compared with the standard card (ICSD number: 98-001-0081), the single-crystal diffraction peaks shown are all close to the (00) of the standard spectrum. l The crystal planes were identified, confirming that the prepared single crystal sample was indeed EuSb2, and that the flaky structure exhibited the ab plane. EDS spectroscopy was used to analyze the elemental content of the prepared single crystal, and the results are as follows: Figure 2 As shown, characteristic peaks for Eu and Sb are observed, with an elemental ratio of 1:2. Combined with the characterization results from XRD and EDS, the invented single-crystal material is confirmed to be EuSb₂.

[0019] The magnetic properties of the prepared single-crystal samples were tested in the temperature range of 300-1.8K. Figure 3 The curve shown is the dependence of magnetization on temperature, which proves that the material is an antiferromagnetic material and the Nell temperature of the magnetic transition is 22.3K.

[0020] Example 2 In this embodiment, the stoichiometric ratio of EuSb2:Tl-Sn is 1:10, and the rest is the same as in Example 1.

[0021] The EuSb2 single crystal structure and properties prepared in this embodiment are similar to those in Example 1.

[0022] Example 3 In this embodiment, the stoichiometric ratio of EuSb2:Tl-Sn is 1:40, and the rest is the same as in Example 1.

[0023] The EuSb2 single crystal structure and properties prepared in this embodiment are similar to those in Example 1.

[0024] Example 4 In this embodiment, the temperature is reduced to 600°C in step (2), and the rest is the same as in embodiment 1.

[0025] The EuSb2 single crystal structure and properties prepared in this embodiment are similar to those in Example 1.

[0026] Comparative Example 1 By changing the type of flux and using Sn as the flux, the parent phases EuSb2 and Sn were weighed at stoichiometric ratios of 1:10 and 1:5 respectively. Following the above growth steps, the muffle furnace program was set to grow at 1000℃ for 10 hours, stabilized for more than one day, slowly cooled to 600℃, and then centrifuged. The final single crystals obtained were Eu2Sb3 and EuSb single crystals, respectively.

[0027] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A method for preparing a single crystal of EuSb2, an antiferromagnetic topological half-metal material, characterized in that: The method steps include: (1) According to the stoichiometric ratio of EuSb2 to Tl-Sn of 1:10~1:40, the raw materials Eu blocks, Tl particles, Sb particles and Sn particles are weighed separately under an environment where the water and oxygen content is less than 0.1 ppm. The raw materials Eu blocks, Tl particles, Sb particles and Sn particles are respectively loaded into quartz tubes, and then the tubes are treated with argon gas in a vacuum sealing system. Finally, hydrogen gas with a pressure of more than 0.8 atmospheres is introduced into the quartz tubes and the hydrogen gas is sealed in the quartz tubes. The above raw materials are annealed at a temperature 50°C lower than their respective melting points to remove the oxide layer on the surface. The purity of the raw material is greater than or equal to 99.999%; The vacuum degree of the vacuum seal is 1×10⁻⁶. -4 Pa or above; (2) Place the quartz tube after vacuum sealing in step (1) into a muffle furnace for firing. The program is set as follows: first, raise the temperature from room temperature to 900~1100℃ in 9h~11h, keep the temperature constant for more than 24h, then lower the temperature to 400~600℃ at a rate of 1~4℃ / h, then open the furnace door, invert the quartz tube and put it into a centrifuge to remove excess products except for single crystals. (3) Open the quartz tube and pick out the single crystal. Some single crystals are stuck together due to the flux. You need to use a blade to cut them along the crystal direction of the single crystal growth to get independent single crystals and obtain a single crystal of an antiferromagnetic topological half-metal material EuSb2. The unit cell parameters of the single crystal are: a=4.7680 Å, b=4.2990 Å, c=8.97 Å, α=γ=90°, β=103.01°.

2. The method for preparing an antiferromagnetic material EuSb2 single crystal as described in claim 1, characterized in that: In step (1), the weighing error of the raw materials is less than or equal to 0.01%.

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