黄铁矿结构CrSb2的高压合成与物性调控研究

Itinerant magnetic metals are important material carriers for studying magnetic quantum critical point and exploring unconventional superconductors. In this project, a new itinerant magnetic material, the high-pressure form of CrSb2 with arsenopyrite-type structure, will be studied detailed characterizations on its high-pressure synthesis and physical property. The ambient-pressure form of CrSb2 exhibits a long range antiferromagnetic order and narrow-band semiconductor behavior. However, CrSb2 synthesized at high temperature and high pressure will transform into arsenopyrite-type structure with high symmetry. In the past reference, CrSb2 has long-range ferromagnetic order and metal behavior, which is a potential itinerant magnetic metal. The high-pressure phase of CrSb2 has been synthesized successfully in my previous work. In addition to observing the ferromagnetic metal behavior, a new antiferromagnetic phase transition has been found in the ambient-pressure form of CrSb2 at low temperature, which show abundant magnetoelectric properties. On this basis, this project intends to carry out meticulous research on the high-pressure form of CrSb2.The physical properties of high-pressure form of CrSb2 will be investigated both by apply the physical pressure and external magnetic field and by chemical substitution with V or Ti for Cr. Through suppressing long-range magnetic order to reach magnetic quantum critical point, we hope to discuss these unconventional properties and explore possible unconventional superconductivity.

巡游磁性金属是研究磁性量子临界点、探索非常规超导体的重要材料载体，本项目拟针对一个新的巡游磁性材料，即具有黄铁矿结构的CrSb2高压相，开展详细的高压合成与物性调控研究。常压下合成的CrSb2具有低对称性的白铁矿结构，表现出长程反铁磁序和窄带半导体行为；而在高温高压条件下合成的CrSb2会转变为高对称性的黄铁矿结构，文献报道其具有长程铁磁序和金属导电行为，因此是潜在的巡游磁性金属。申请人在前期工作中成功合成了CrSb2的高压相，除了观察到铁磁金属行为外，还在低温发现了一个新的反铁磁相变，表现出更加丰富的磁电现象。在此基础上，本项目拟对黄铁矿结构的CrSb2高压相开展深入细致的调控研究，一方面对其施加物理压力和外加磁场进行外场调控，另一方面通过Cr位掺杂V或者Ti进行化学调控，通过抑制长程磁有序实现磁性量子临界点，研究与之相关的反常物性并探索可能的非常规超导电性。

采用高温高压合成了黄铁矿结构CrSb2多晶材料，并对其物理性质进行了详细的研究。研究发现CrSb2高压相转变为金属，而且在降温时会出现两个连续的磁转变，首先在~160 K发生铁磁转变，然后在~86 K出现反铁磁转变。在常压下施加外磁场，会逐渐抑制低温的反铁磁转变，在3T以上获得铁磁金属基态。而施加高压时，反铁磁转变迅速往高温移动，铁磁转变往低温移动，二者相遇后系统基态转变为反铁磁金属，进一步增加压力会逐渐抑制反铁磁转变，在~9 GPa时被完全压制，实现反铁磁量子临界点。此外，通过Cr位掺杂V或者Ti进行化学调控，通过抑制长程磁有序实现磁性量子临界点，研究与之相关的反常物性并探索可能的非常规超导电性。