Cr2(Ge/Si)2Te6单晶中的电热磁耦合效应研究

电子参与能带的形成，其自旋和轨道运动产生的磁矩影响着晶体的磁学性质，而其迁移也影响着晶体的电学性能，故而材料的磁学性质与其电热输运性能密切相关。然而电子的自旋和轨道耦合的原子磁矩及其排列方式与热电性能的关联规律及相关物理机制尚不清楚，相关研究对热电材料性能突破至关重要，有望成为热电领域研究的前沿。Cr2(Ge/Si)2Te6是铁磁半导体，同时具备潜在的优异热电性能。本项目以Cr2(Ge/Si)2Te6单晶为研究对象，研究其电/热/磁输运行为，阐明有序磁矩的取向和大小与材料电声输运性质的关联规律及相关物理机制；研究磁性离子掺杂引入的局域磁矩对电声相互作用的影响规律；通过施加外磁场，发展磁有序—局域磁矩—外磁场的“一体化”协同调控方案，显著提升Cr2(Ge/Si)2Te6单晶样品热电性能。该项目研究成果对揭示具备磁有序或外磁场下的晶体中电子-声子-自旋耦合新机制和新效应具有重要科学意义。

The magnetic properties of crystalline materials are primarily affected by the magnetic moments generated from the spin and orbital motion of the electron, meanwhile, their electrical properties are partially manipulated by the migration of the valence electrons involved in the formation of electronic bands. Therefore, the magnetic properties in crystalline materials are closely related to their electrical-thermal transport properties. Nevertheless, it is still ambiguous that the corresponding physical mechanisms of thermoelectric performances in relation to the atomic magnetic moment along with its arrangement of the electron and orbital coupling, which drives us to investigate the magneton-phonon-electron interaction as well as the physical principles and mechanisms in thermoelectric materials. It is expected that the related studies are deemed to be critical for the breakthrough of the thermoelectric properties and promise potential frontier research direction in the thermoelectricity field. Cr2(Ge/Si)2Te6 is not only a ferromagnetic semiconductor with curie temperature of ~62 K, but also a material with potential thermoelectric performance, which is a good choice for the study of magneto-thermo-electric effects. In this project, by optimizing the synthesis parameters, we will fabricate high quality Cr2(Ge/Si)2Te6 based single crystal with layered crystalline structure. We will study the electric, thermal and magnetic behavior for Cr2(Ge/Si)2Te6 system systematically and explored the relationship between the spin ordering and electron/phonon transport properties. Furthermore, the manipulation of localized magnetic field will be realized by magnetic doping and the corresponding impact on the thermoelectric performance will be demonstrated. Finally, a synergistic strategy to optimize the electron/phonon transport properties via further applying the external magnetic field will be proposed, leading to an improved ZT value. The achievements will be a good example for solving a key and fundamental issue of magneto-thermal-electric coupling effects in thermoelectric materials.