Heavy Fermi material as well as preparation method and application thereof

Abstract

The invention relates to a heavy Fermi material as well as a preparation method and application thereof, belongs to the technical field of heavy Fermi materials, and is used for solving at least one of the problems of many impure phases, poor crystallinity, poor magnetic performance and the like of the heavy Fermi material prepared by the existing method. The invention relates to a heavy Fermi material, the chemical formula of the heavy Fermi material is Ce3PnAs5, and Pn is V, Mn or Cr. The heavy Fermi material prepared by the method has no impure phase and better crystallization property, shows ferromagnetic-like characteristics, has potential application prospects in the aspects of electromagnetic device preparation and the like, and provides a good material basis for regulation and control of quantum critical points, exploration of unconventional superconductors and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy fermion materials, and particularly relates to a heavy fermion material, a preparation method thereof, and an application thereof. Background Art

[0002] Heavy fermions refer to conduction electrons in certain rare-earth element-containing metals or alloys that have an effective mass 2 - 3 orders of magnitude larger than that of free electrons, and are usually present in lanthanide or actinide intermetallic compounds containing local f-electrons. Generally, it is considered that there are two competing forces in heavy fermion compounds, namely the Kondo interaction and the RKKY interaction: Through the Kondo effect, the local magnetic moments in the heavy fermion system are screened by conduction electrons, making the system tend to a non-magnetic ground state, and at the same time significantly increasing the effective mass of electrons, from which heavy fermions get their name; on the other hand, long-range RKKY magnetic exchange interactions will be generated between spatially more local f-electrons or d-electrons through the mediation of itinerant electrons, thus forming long-range magnetic order. The ground state of the heavy fermion system depends on the competition between the Kondo effect and the RKKY interaction, showing rich ground state properties. In such materials, the interaction between degrees of freedom such as spin, charge, orbit, and lattice may lead to quantum states such as magnetic order, unconventional superconductivity, mixed valence states, non-Fermi liquids, and topological order, and may be accompanied by quantum critical fluctuations such as spin, charge, and orbit, showing unique quantum critical behavior.

[0003] In condensed matter physics, low-dimensional spin systems have attracted much attention due to their unique physical phenomena. Compared with high-dimensional systems, one-dimensional spin systems exhibit many novel physical properties, such as superconducting phenomena, significant magnetic anisotropy, and quantum phase transitions. Such systems not only have important theoretical research value, but also provide an ideal research platform for exploring high-dimensional magnetic systems. It should be noted that in real material systems, a strictly one-dimensional structure is difficult to achieve. When one-dimensional spin chains are arranged in space, interactions will inevitably occur between the chains, thus forming spin chain materials with quasi-one-dimensional characteristics. Such quasi-one-dimensional materials, relying on their special crystal structures and physical properties such as magnetic anisotropy, can break through the limitations of traditional isotropic ferromagnetic materials in electromagnetic properties, providing new ideas and directions for the research and development of new electromagnetic functional materials.

[0004] Quasi-one-dimensional heavy fermion magnetic materials exhibit extremely complex and unique physical behaviors, and are closely related to material systems such as multiferroic materials and high-temperature superconductors. In-depth study of the physical properties of these materials can not only improve the understanding of the mechanisms behind related strange phenomena, but also have important guiding significance for the discovery and development of new functional materials. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a heavy fermion material, a preparation method and an application thereof, so as to solve at least one of the problems such as many impurity phases, poor crystallinity, and poor magnetic properties of the heavy fermion material prepared by the existing methods.

[0006] In a first aspect, the present invention provides a heavy fermion material, and the chemical formula of the heavy fermion material is Ce 3 PnAs 5 , where Pn is V, Mn or Cr.

[0007] In a second aspect, the present invention provides a preparation method of the heavy fermion material, comprising the following steps:

[0008] (1) Grinding Ce powder and As powder, vacuum-sealing, and calcining to obtain CeAs powder;

[0009] (2) Mixing and grinding the CeAs powder, metal Pn powder and As powder to obtain a mixture;

[0010] (3) Pressing the mixture into a cylinder and sintering to obtain the heavy fermion material.

[0011] Further, in step (1), the molar ratio of Ce powder to As powder is 1:1.

[0012] Further, in step (1), the calcining temperature is 600-800 °C, and the calcining holding time is 8-10 h.

[0013] Further, in step (1), the vacuum degree of the vacuum-sealing is <10 -3 Pa.

[0014] Further, in step (1), grinding is carried out in an Ar environment.

[0015] Further, in step (2), the molar ratio of the CeAs powder, metal Pn powder and As powder is 3:1:2.

[0016] Further, in step (3), the ratio of the height to the diameter of the cylinder is 1:12 to 1:2.

[0017] Further, in step (3), the sintering pressure is 5-7 GPa, the temperature is 1401-1500 °C, and the sintering time is 0.5-2 h.

[0018] In a third aspect, the present invention provides an electromagnetic device, comprising the above heavy fermion material.

[0019] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0020] (1) The present invention has prepared a novel quasi-one-dimensional spin-chain heavy fermion material Ce 3 PnAs 5 , where Pn is V, Cr or Mn, belonging to the hexagonal crystal system, with the space group P6 3 / mcm and the corresponding space group number 193. In the crystal structure of the heavy fermion material, along the c-axis direction, Ce atoms located at the 6g sites form a zigzag chain, and the PnAs 6 (Pn = V, Cr, Mn) octahedrons connected by face-sharing form a one-dimensional chain. The chains are arranged parallel to each other, and the distance between the chains is the lattice constant a, having obvious one-dimensional characteristics;

[0021] (2) The heavy fermion material prepared by the method of the present invention is single-phase, with better crystallization performance, showing ferromagnetic-like characteristics, and having potential application prospects in the preparation of electromagnetic devices (such as field effect transistors or optoelectronic devices), providing a good material basis for regulating quantum critical points and exploring unconventional superconductors, etc.

[0022] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be made obvious from the description, or understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained from the content specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are only for the purpose of showing specific embodiments and are not considered as limiting the present invention. Throughout the drawings, the same reference signs represent the same components.

[0024] Figure 1 It is the magnetic test diagram of the heavy fermion material prepared in Example 1 of the present invention;

[0025] Figure 2 It is the magnetic test diagram of the heavy fermion material prepared in Example 2 of the present invention;

[0026] Figure 3 It is the magnetic test diagram of the heavy fermion material prepared in Example 3 of the present invention;

[0027] Figure 4 It is the resistivity diagram of the heavy fermion material prepared in Example 1 of the present invention;

[0028] Figure 5 It is the resistivity diagram of the heavy fermion material prepared in Example 2 of the present invention;

[0029] Figure 6 It is the resistivity diagram of the heavy fermion material prepared in Example 3 of the present invention;

[0030] Figure 7 Specific heat capacity diagram of the heavy fermion material prepared in Example 1 of the present invention;

[0031] Figure 8 Specific heat capacity diagram of the heavy fermion material prepared in Example 2 of the present invention;

[0032] Figure 9 Specific heat capacity diagram of the heavy fermion material prepared in Example 3 of the present invention;

[0033] Figure 10 Resistivity comparison diagram of the heavy fermion materials prepared in Examples 1 - 3 of the present invention and the material prepared in Comparative Example 5;

[0034] Figure 11 XRD refinement diagram of the material prepared in Example 1 of the present invention;

[0035] Figure 12 XRD refinement diagram of the material prepared in Example 2 of the present invention;

[0036] Figure 13 XRD refinement diagram of the material prepared in Example 3 of the present invention;

[0037] Figure 14 XRD diagram of the materials prepared in Comparative Examples 1 - 4 of the present invention. Detailed implementation manners

[0038] The following will specifically describe the preferred embodiments of the present invention with reference to the accompanying drawings. Among them, the drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principle of the present invention, rather than to limit the scope of the present invention.

[0039] A specific embodiment of the present invention discloses a heavy fermion material, and the chemical formula of the heavy fermion material is Ce 3 PnAs 5 , where Pn is V, Mn or Cr.

[0040] Another specific embodiment of the present invention discloses a preparation method of a heavy fermion material, which includes the following steps:

[0041] (1) Grind Ce powder and As powder, vacuum seal and calcine to obtain CeAs powder;

[0042] (2) Mix and grind the CeAs powder, metal Pn powder and As powder to obtain a mixture;

[0043] (3) Press the mixture into a cylinder and sinter to obtain the heavy fermion material.

[0044] Specifically, in step (1), the molar ratio of Ce powder to As powder is 1:1. Preferably, it is ground in an Ar environment.

[0045] Specifically, in step (1), the vacuum degree of the vacuum seal is < 10 -3 Pa. Preferably, the ground material is loaded into a quartz tube for vacuum sealing.

[0046] It should be noted that in a vacuum environment, the reactants are prevented from being oxidized.

[0047] Specifically, in step (1), the calcination temperature is 600 - 800 °C, for example, 620 °C, 640 °C, 660 °C, 680 °C, 700 °C, 720 °C, 740 °C, 760 °C, 780 °C, and the calcination holding time is 8 - 10 h, for example, 8.2 h, 8.4 h, 8.6 h, 8.8 h, 9.0 h, 9.2 h, 9.4 h, 9.6 h, 9.8 h.

[0048] It should be noted that under the above calcination temperature and holding time, the reaction can be ensured to be complete while reducing energy consumption and avoiding the melting of the quartz tube.

[0049] Specifically, in step (2), the molar ratio of the CeAs powder, metal Pn powder, and As powder is 3:1:2.

[0050] Preferably, Pn is V, Mn, or Cr.

[0051] Specifically, in step (3), the ratio of the height to the diameter of the cylinder is 1:12 to 1:2.

[0052] Preferably, the diameter of the cylinder is 12 mm and the height is 1 - 6 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm.

[0053] It should be noted that the height of the cylinder can ensure that the sample is within a reasonable range of pressure gradient and temperature gradient, and the reaction is fully completed.

[0054] Specifically, in step (3), the sintering pressure is 5 - 7 GPa, for example, 5.2 GPa, 5.4 GPa, 5.6 GPa, 5.8 GPa, 6.0 GPa, 6.2 GPa, 6.4 GPa, 6.6 GPa, 6.8 GPa, the temperature is 1401 - 1500 °C, for example, 1410 °C, 1420 °C, 1430 °C, 1440 °C, 1450 °C, 1460 °C, 1470 °C, 1480 °C, 1490 °C, and the sintering time is 0.5 - 2 h, for example, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h.

[0055] It should be noted that the above sintering conditions can ensure complete reaction, achieve the required crystallinity and reduce energy consumption.

[0056] The heavy fermion material prepared by the method of the present invention is single-phase, has better crystallization performance, and exhibits ferromagnetic characteristics. It has potential application prospects in the preparation of electromagnetic devices, etc., and provides a good material basis for regulating quantum critical points and exploring unconventional superconductors.

[0057] Another specific embodiment of the present invention discloses an electromagnetic device, comprising the above-mentioned heavy fermion material.

[0058] Preferably, the electromagnetic device includes a field effect transistor or an optoelectronic device.

[0059] The technical solution of the present invention is further explained below in conjunction with specific embodiments, wherein the purity of Ce powder is ≥99.9%, the purity of As powder is ≥99.9%, and the purity of metal Pn powder is ≥99.9%.

[0060] Example 1

[0061] A heavy fermion material of this embodiment, the chemical formula of the heavy fermion material is Ce 3 VAs 5 The preparation method of the heavy fermion material of this embodiment is as follows:

[0062] (1) Use high-purity Ce powder and As powder as raw materials, weigh them according to the molar ratio of 1:1, grind them evenly, and seal them in a vacuum of less than 10 -3 Pa quartz tube, calcined at 600 ° C for 10 h, and cooled naturally to obtain CeAs powder;

[0063] (2) weighing the CeAs powder, metal V powder and As powder according to a molar ratio of 3:1:2, grinding and mixing them uniformly to obtain a mixture;

[0064] (3) The mixture is pressed into a cylinder with a diameter of 12 mm and a height of 6 mm using a mold and a tablet press, and then the cylinder is placed in a high-pressure synthesis device, sintered at a pressure of 5.5 GPa and a temperature of 1401° C. for 0.5 h, and naturally cooled to obtain the heavy fermion material.

[0065] Example 2

[0066] A heavy fermion material of this embodiment, the chemical formula of the heavy fermion material is Ce 3 CrAs 5 The preparation method of the heavy fermion material of this embodiment is as follows:

[0067] (1) Using high-purity Ce powder and As powder as raw materials, weigh them according to a molar ratio of 1:1, grind them evenly and seal them in a quartz tube with a vacuum degree < 10 -3 Pa, calcine at 700 °C for 9 h, and cool naturally to obtain CeAs powder;

[0068] (2) Weigh the CeAs powder, metal Cr powder and As powder according to a molar ratio of 3:1:2, grind and mix them evenly to obtain a mixture;

[0069] (3) Press the mixture into a cylinder with a diameter of 12 mm and a height of 3 mm using a mold and a tablet press, then place the cylinder in a high-pressure synthesis device, and perform high-temperature sintering at a pressure of 6.5 GPa and a temperature of 1500 °C for 1 h, and cool naturally to obtain the heavy fermion material.

[0070] Example 3

[0071] A heavy fermion material in this example, the chemical formula of the heavy fermion material is Ce 3 MnAs 5 , and the preparation method of the heavy fermion material in this example is as follows:

[0072] (1) Using high-purity Ce powder and As powder as raw materials, weigh them according to a molar ratio of 1:1, grind them evenly and seal them in a quartz tube with a vacuum degree < 10 -3 Pa, calcine at 800 °C for 8 h, and cool naturally to obtain CeAs powder;

[0073] (2) Weigh the CeAs powder, metal Mn powder and As powder according to a molar ratio of 3:1:2, grind and mix them evenly to obtain a mixture;

[0074] (3) Press the mixture into a cylinder with a diameter of 12 mm and a height of 1 mm using a mold and a tablet press, then place the cylinder in a high-pressure synthesis device, and perform high-temperature sintering at a pressure of 7 GPa and a temperature of 1450 °C for 2 h, and cool naturally to obtain the heavy fermion material.

[0075] Comparative Example 1

[0076] The preparation method of the material in this comparative example is as follows:

[0077] (1) Mix Ce powder, Mn powder and As powder according to a molar ratio of 3:1:5, grind them evenly to obtain a mixture;

[0078] (2) Press the above-mentioned mixture into a cylinder with a diameter of 12 mm and a height of 6 mm by using a mold and a tablet press, then put the cylinder into a high-pressure synthesis device, and conduct high-temperature sintering at a pressure of 7 GPa and a temperature of 1450 °C for 2 h, and then cool it naturally to obtain the material.

[0079] Comparative Example 2

[0080] The preparation method of the material in this comparative example is as follows:

[0081] (1) Mix Ce powder, V powder and As powder in a molar ratio of 3:1:5, and grind them evenly to obtain a mixture;

[0082] (2) Press the above-mentioned mixture into a cylinder with a diameter of 12 mm and a height of 6 mm by using a mold and a tablet press, then put the cylinder into a high-pressure synthesis device, and conduct high-temperature sintering at a pressure of 5.5 GPa and a temperature of 1401 °C for 0.5 h, and then cool it naturally to obtain the material.

[0083] Comparative Example 3

[0084] The chemical formula of the material in this comparative example is the same as that in Example 1, the difference is that in step (3), the diameter of the cylinder is 12 mm and the height is 7 mm.

[0085] Comparative Example 4

[0086] The chemical formula of the material in this comparative example is the same as that in Example 1, the difference is that in step (3), the sintering pressure is 4 GPa and the sintering temperature is 1350 °C.

[0087] Comparative Example 5

[0088] Prepare three groups of materials by the method of this comparative example, and the chemical formulas are La 3 VAs 5 , La 3 CrAs 5 , La 3 MnAs 5 .

[0089] Using high-purity La powder, Pn (Pn is V, Cr or Mn) powder and As powder as raw materials, accurately weigh the three according to the molar ratio of La:Pn:As of 3:1:5, and grind and mix them evenly to obtain a mixture. Use a mold to press the ground and mixed mixture into a cylinder with a diameter of 6 mm and a height of 3 mm by a tablet press, then put the obtained cylinder into a high-pressure synthesis assembly block, and conduct high-temperature and high-pressure sintering at a pressure of 5 GPa and a temperature of 1300 °C for 0.5 h. After the sintered product is naturally cooled to room temperature, a ferromagnetic metal material is obtained.

[0090] Test Example 1

[0091] 1. The magnetic susceptibilities of the heavy fermion materials prepared in Examples 1-3 were measured separately. As Figures 1-3 shown, the resistivity was as Figures 4-6 shown, and the specific heat capacity was as Figures 7-9 shown. The resistivity comparison chart of the heavy fermion materials prepared in Examples 1-3 and the material prepared in Comparative Example 5 was as Figure 10 shown.

[0092] According to Figures 1-9 the magnetic, resistance, and specific heat measurements, for the Ce 3 PnAs 5 materials, as Pn changes from V to Cr and then to Mn, the Ce 3 PnAs 5 materials gradually transition from ferromagnetic-like to ferrimagnetic, the Kondo effect gradually strengthens, and the heavy fermion characteristics become more prominent.

[0093] As Figure 10 shown, the resistance measurement shows that the resistivity of the Ce 3 PnAs 5 material is much higher than that of the La 3 PnAs 5 material, and different from the La 3 PnAs 5 material whose resistivity monotonically decreases when the temperature drops, for the Ce 3 PnAs 5 the resistivity first rises and then falls, which also confirms that the Kondo interaction reflecting the heavy fermion physical properties in the Ce 3 PnAs 5 material is more significant than that in the La 3 PnAs 5 material.

[0094] As Figure 1 shown, the ferromagnetic Curie temperature of Ce 3 VAs 5 is 13.6K. The magnetic measurement shows that a paramagnetic to ferromagnetic transition occurs in the sample at 13.6K, and there is also an obvious change in the specific heat measurement at 13.6K. The heavy fermion specific heat coefficient of the sample is calculated to be 360 mJ / (K 2 Ce-mol). The resistance measurement observes that when the temperature drops to about 100K, the resistance drop rate starts to increase significantly, which is caused by the combined action of the Kondo effect and the crystal field effect. The magnetic, resistance, and specific heat measurements confirm that a ferromagnetic-like transition occurs in the sample at 13.6K, and there is a typical Kondo interaction in the heavy fermion material.

[0095] As Figure 2 shown, Ce 3 CrAs 5The ferromagnetic Curie temperature is 6 K. Magnetic measurements show that a paramagnetic to ferromagnetic transition occurs in the sample at 6 K, and an inflection point of magnetic behavior appears around 13 K. Meanwhile, there are also obvious changes in the specific heat measurement at 4 K. Resistance measurements observe that as the temperature decreases, the resistance first increases and then decreases, with an extreme point around 40 K, which is caused by the combined action of the Kondo effect and the crystal field effect, showing typical behavior of heavy fermion materials.

[0096] As Figure 3 shown, Ce 3 MnAs 5 The ferromagnetic Curie temperature is 6 K. Magnetic measurements show that an antiferromagnetic-like transition occurs in the sample at 6 K, and ferromagnetic transitions occur at 3.4 K and 27.4 K. There should be a small peak near 6 K in the specific heat measurement, but the signal is masked by the stronger Kondo effect. Resistance measurements observe that as the temperature decreases, the resistance first increases, then decreases, and then increases again, with extreme points at 27.6 K and 3.6 K, which is consistent with the results of magnetic measurements. This is caused by the combined action of the Kondo effect and the crystal field effect, showing typical behavior of heavy fermion materials.

[0097] 2. The XRD patterns of the materials prepared in Examples 1-3 and Comparative Examples 1-4 were tested separately, and the results are as Figures 11-14 shown.

[0098] By comparing Comparative Examples 1-4 with Examples 1-3, it can be seen that the materials prepared in Comparative Examples 1-4 have more impurity phases, poorer crystallinity, and lower purity.

[0099] The X-ray diffraction pattern analysis results of the heavy fermion materials prepared in Examples 1-3 show that the samples of the heavy fermion materials prepared by the method of the present invention are all single-phase, with the chemical formula Ce 3 PnAs 5 , where Pn is V, Mn, or Cr. The crystal structure is hexagonal, the space group is P6 3 / mcm, corresponding to the space group number 193. In the crystal structure of the heavy fermion material, along the c-axis direction, Ce atoms located at the 6g site form a zigzag chain, and the PnAs 6 (Pn = V, Cr, Mn) octahedrons connected by face-sharing form a one-dimensional chain. The chains are arranged parallel to each other, and the distance between the chains is the lattice constant a, showing obvious one-dimensional characteristics.

[0100] Among them, the lattice parameters of Ce 3 VAs 5 are The lattice parameters of Ce 3 CrAs 5 are The lattice parameters of Ce 3 MnAs 5 are According to Ce 3 PnAs 5 (Pn = V, Cr, Mn), the lattice parameter a value obtained by structure refinement is large enough, further determining that this type of material is a quasi-one-dimensional structure.

[0101] Due to the presence of 4f 1 electrons in Ce, Ce exhibits magnetism, bringing about relatively complex magnetic exchange interactions in the Ce 3 PnAs 5 materials. Therefore, before preparing this type of material, it is necessary to first prepare the CeAs powder precursor, and there are obvious differences in technical parameters such as pressure, temperature, and synthesis time compared with the preparation of La 3 PnAs 5 materials.

[0102] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A heavy fermion material, characterized in that: The chemical formula of the heavy fermion material is Ce3PnAs5, wherein Pn is V, Mn or Cr.

2. A method for preparing the heavy fermion material according to claim 1, characterized in that: The steps include: (1) grinding Ce powder and As powder, vacuum sealing, and calcining to obtain CeAs powder; (2) mixing and grinding the CeAs powder, metal Pn powder and As powder to obtain a mixture; (3) Pressing the mixture into a cylinder and sintering it to obtain the heavy fermion material.

3. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of Ce powder to As powder is 1:

1.

4. The preparation method according to claim 2, characterized in that: In step (1), the calcination temperature is 600-800° C., and the calcination holding time is 8-10 hours.

5. The preparation method according to claim 2, characterized in that: In step (1), the vacuum degree of the vacuum seal is less than 10 - 3 Pa.

6. The preparation method according to claim 2, characterized in that: In step (1), grinding is performed in an Ar environment.

7. The preparation method according to any one of claims 2 to 6, characterized in that: In step (2), the molar ratio of the CeAs powder, the metal Pn powder and the As powder is 3:1:

2.

8. The preparation method according to any one of claims 2 to 6, characterized in that: In step (3), the ratio of the height to the diameter of the cylinder is 1:12 to 1:

2.

9. The preparation method according to any one of claims 2 to 6, characterized in that: In step (3), the sintering pressure is 5 to 7 GPa, the temperature is 1401 to 1500° C., and the sintering time is 0.5 to 2 h.

10. An electromagnetic device, characterized in that: The invention comprises the heavy fermion material according to claim 1 or the heavy fermion material prepared by any one of the methods of claims 2-9.

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