intermetallic compounds

Abstract

To provide a new intermetallic compound exhibiting unique magnetic properties.SOLUTION: An intermetallic compound of a certain aspect comprises chromium (Cr) and germanium (Ge), and a molar ratio γ(Ge / Cr) of germanium with respect to chromium satisfies 1.727<γ<1.746 and 1.755≤γ<1.78.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to intermetallic compounds.

Background Art

[0002] Among intermetallic compounds M m X x (1.25 < x / m < 2) composed of group 4-9 transition metal M and group 13-15 semimetal element X, there are many substances having similar crystal structures. This structure has an atomic arrangement in which a ladder made of X atoms ascends in a spiral staircase shape inside a square prism chimney formed by M atoms, and is called a chimney-ladder (CL) structure. Among compounds having the CL structure (hereinafter also referred to as CL compounds), there are substances showing peculiar properties in terms of magnetic and thermoelectric properties. For example, Cr 11 Ge 19 (CrGe 1.727 ) shows ferromagnetism at a Curie temperature (Tc) = 72K (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a result of intensive studies on Cr-Ge-based CL compounds, the present inventors have found a new intermetallic compound showing unique magnetic properties.

[0005] An object of the present disclosure is to provide a new intermetallic compound showing unique magnetic properties.

Means for Solving the Problems

[0006] One embodiment of the present disclosure is an intermetallic compound that includes chromium (Cr) and germanium (Ge), and the molar ratio of germanium to chromium, γ (Ge / Cr), satisfies 1.727<γ<1.746 and 1.755≦γ<1.78. [Effects of the Invention]

[0007] According to the present disclosure, a new intermetallic compound exhibiting unique magnetic properties can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams for explaining the crystal structure of an intermetallic compound according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an XRD pattern of a sample of Comparative Example 1. [Figure 3] FIG. 1 is a diagram showing an XRD pattern of a sample of Example 1. [Figure 4] FIG. 1 shows an XRD pattern of the sample of Example 2. [Figure 5] FIG. 1 shows an XRD pattern of the sample of Example 3. [Figure 6] FIG. 1 shows an XRD pattern of the sample of Example 4. [Figure 7] FIG. 10 is a diagram showing the temperature dependence of magnetization of the sample of Comparative Example 1 in a magnetic field H=100 Oe. [Figure 8] FIG. 1 is a diagram showing the temperature dependence of magnetization of the sample of Example 1 in a magnetic field H=100 Oe. [Figure 9] FIG. 10 is a diagram showing the temperature dependence of magnetization of the sample of Example 2 in a magnetic field H=100 Oe. [Figure 10] FIG. 10 is a diagram showing the temperature dependence of magnetization of the sample of Example 3 in a magnetic field H=100 Oe. [Figure 11] FIG. 10 is a diagram showing the temperature dependence of magnetization of the sample of Example 4 in a magnetic field H=100 Oe. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments for carrying out the present disclosure will be described in detail with reference to the drawings, etc. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0010] The intermetallic compound according to the embodiment contains chromium (Cr) and germanium (Ge), and the molar ratio γ of germanium to chromium (Ge / Cr) satisfies 1.727<γ<1.746 and 1.755≦γ<1.78. This intermetallic compound is a soft magnetic material and exhibits ferromagnetism. Therefore, this intermetallic compound can be suitably used as a magnetic material for magnetic devices and the like.

[0011] The intermetallic compound according to the embodiment may have a chimney ladder type crystal structure. This crystal structure will be explained with reference to Fig. 1. In general, an intermetallic compound formed by a metal M from Groups 4 to 9 and an element X from Groups 13 to 15 is m X x (MX γ As shown in Figure 1, M m X x It has a structure that looks like a ladder made of X atoms climbing up a spiral staircase in a chimney made of metal M atoms, and is an "incommensurate composite crystal" consisting of two sublattices with different c-axis lengths. The c-axis lengths of these two sublattices are respectively c M , c X Then, the CL type crystal structure is a, b, c M , c X The CL crystal structure can be expressed by the (3+1)-dimensional superspace group I41 / amd(00γ)00ss, which takes into account the four crystal axes. In the CL crystal structure, the ratio γ of the c-axis lengths also corresponds to the composition ratio X / M. In an embodiment, the metal M is chromium, the element M is germanium, and γ satisfies 1.727<γ<1.746 and 1.755≦γ<1.78.

[0012] The intermetallic compound according to the embodiment may be one in which part of germanium is substituted with another element, or one in which an element other than chromium or germanium is inserted between atoms.

[0013] The intermetallic compound according to the embodiment exhibits ferromagnetism over a wide temperature range, and can exhibit ferromagnetism even at temperatures above room temperature. The intermetallic compound according to the embodiment preferably has a Curie temperature of 293 K or higher. Here, the Curie temperature in the embodiment means a value obtained by measuring the temperature dependence of magnetization.

[0014] The intermetallic compound according to the embodiment can be produced, for example, as described in the Examples below. Specifically, a raw material powder can be prepared by weighing and mixing germanium powder and chromium powder so that the molar ratio γ (Ge / Cr) is 1.727<γ<1.746 or 1.755≦γ<1.78. This raw material powder, or a raw material prepared by melting the raw material powder and solid-state synthesis, can be pressurized and heated, for example, at 2 GPa or higher and a temperature of 600 to 1000°C using a high-pressure generator, to produce the intermetallic compound according to the embodiment.

[0015] The intermetallic compounds according to the embodiments can exhibit ferromagnetism at temperatures around room temperature or higher, and therefore can be suitably used as magnetic materials for magnetic devices such as magnetoresistance effect elements and magnetic memories. [Example]

[0016] Hereinafter, the embodiments will be described in more detail with reference to examples, but these examples do not limit the present disclosure in any way.

[0017] In the following examples and comparative examples, Ge chunks and Cr powders were used as raw materials. After crushing the Ge chunks, the Ge powder and Cr powder were weighed out in a predetermined molar ratio, and the mixed raw materials were melted and subjected to solid-phase synthesis to prepare a sample or mixed powder. This was used as the starting sample.

[0018] The X-ray diffraction measurement of the samples of the examples and comparative examples was performed by powder X-ray diffraction, and the magnetization measurement was performed by the electromagnetic induction method using a high-sensitivity magnetometer.

[0019] (Comparative Example 1) A starting sample with a molar ratio of Gr:Ce = 4:7 was filled into a sample capsule to prepare a high-pressure experimental cell. A multi-anvil high-pressure generator was used as the pressure generator. After pressurizing to 5 GPa, the sample was heated to 1000°C and held there for 60 minutes. After heating, the sample was rapidly cooled, depressurized, and recovered at room temperature and pressure. The recovered sample was evaluated by X-ray diffraction and magnetization measurements.

[0020] Example 1 A starting sample with a molar ratio of Gr:Ce = 1:1.77 was filled into a sample capsule to prepare a high-pressure experimental cell. A multi-anvil high-pressure generator was used as the pressure generator. After pressurizing to 2 GPa, the sample was heated to 700°C and held there for 60 minutes. After heating, the sample was rapidly cooled, depressurized, and recovered at room temperature and pressure. The recovered sample was evaluated by X-ray diffraction and magnetization measurements.

[0021] Example 2 Except for the molar ratio being 1.77 and the synthesis pressure being 7 GPa, the sample of Example 2 was obtained in the same manner as in Example 1. The obtained sample was evaluated by X-ray diffraction measurement and magnetization measurement.

[0022] Example 3 A sample of Example 3 was obtained in the same manner as in Example 1, except that the molar ratio was 1.77 and the synthesis pressure was 10 GPa. The obtained sample was evaluated by X-ray diffraction measurement and magnetization measurement.

[0023] Example 4 A sample of Example 4 was obtained in the same manner as in Example 1, except that the molar ratio was 1.77 and the synthesis pressure was 14 GPa. The obtained sample was evaluated by X-ray diffraction measurement and magnetization measurement.

[0024] Figure 2 shows the XRD pattern of the sample of Comparative Example 1. In Comparative Example 1, peaks appeared at angles very close to those of Cr4Ge7. These peaks were determined to be the CL compound Crm Ge x When LeBail analysis was performed using the superspace group, the composition ratio x / m was found to be 1.747, which is close to the composition ratio x / m = 1.75 of Cr4Ge7.

[0025] 3 shows the XRD pattern of the sample of Example 1. When the diffraction peak of Example 1 was subjected to LeBail analysis using the CL compound as in Comparative Example 1, x / m of Example 1 was found to be 1.737.

[0026] 4 shows the XRD pattern of the sample of Example 2. When the diffraction peak of Example 2 was subjected to LeBail analysis using the CL compound as in Comparative Example 1, x / m of Example 2 was found to be 1.755.

[0027] 5 shows the XRD pattern of the sample of Example 3. When the diffraction peak of Example 3 was subjected to LeBail analysis using the CL compound as in Comparative Example 1, x / m of Example 3 was found to be 1.763.

[0028] 6 shows the XRD pattern of the sample of Example 4. When the diffraction peak of Example 4 was subjected to LeBail analysis using the CL compound as in Comparative Example 1, x / m of Example 4 was found to be 1.774.

[0029] Magnetization measurements were performed on the samples of Comparative Example 1 and Examples 1 to 4. The temperature dependence of magnetization for these samples at a magnetic field H of 100 Oe is shown in Figures 7 to 11, respectively. All samples exhibited ferromagnetic behavior. The Curie temperature of the sample of Comparative Example 1 (x / m = 1.747) was Tc = 177 K. The Curie temperature of the sample of Example 1 (x / m = 1.737) was Tc = 143 K. The Curie temperature of the sample of Example 2 (x / m = 1.755) was Tc = 250 K. The Curie temperature of the sample of Example 3 (x / m = 1.763) was Tc = 298 K. The Curie temperature of the sample of Example 4 (x / m = 1.774) was Tc = 339 K. These results reveal that, among Cr-Ge-based CL compounds, compounds with a more germanium-rich composition exhibit higher Curie temperatures.

[0030] The present disclosure has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and the respective treatment processes, and that such modifications are also within the scope of the present disclosure. [Industrial Applicability]

[0031] The intermetallic compounds of the present disclosure can be used as magnetic materials for magnetic devices and the like.

Claims

1. It is composed of chromium (Cr) and germanium (Ge), and the molar ratio of germanium to chromium γ (Ge / Cr) is 1.737≦γ<1.746 or 1.755≦γ≦1.763 or γ=1.774 is an intermetallic compound.

2. The intermetallic compound according to claim 1, wherein the intermetallic compound has a chimney-ladder type crystal structure.

3. 3. The intermetallic compound according to claim 1, wherein the intermetallic compound exhibits ferromagnetic properties.

4. 4. The intermetallic compound according to claim 1, wherein the Curie temperature is 293K to 339K.

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