ABSTRACT

The interplay between charges and spins may influence the dynamics of the carriers and determine their thermoelectric properties. In that respect, magneto-thermoelectric power MTEP, i.e. the measurements of the Seebeck coefficient S under the application of an external magnetic field, is a powerful technique to reveal the role of magnetic moments on S. This is illustrated by different transition metal chalcogenides: CuCrTiS₄ and CuMnTiS₄ magnetic thiospinels, which are compared with magnetic oxides, Curie-Weiss (CW) paramagnetic misfit cobaltites, ruthenates, either ferromagnetic perovskite or Pauli paramagnet quadruple perovskites, and CuGa_1-xMn_xTe₂ chalcopyrite telluride and Bi_1.99Cr_0.01Te₃ in which diluted magnetism is induced by 3%-Mn and 1%-Cr substitution, respectively. In the case of a ferromagnet (below T_C) and CW paramagnetic materials, the increase of magnetization at low T when a magnetic field is applied is accompanied by a decrease of the entropy of the carriers and hence $\left|S\right|$ decreases. This is consistent with the lack of MTEP in the Pauli paramagnetic quadruple perovskites. Also, no significant MTEP is observed in CuGa_1-xMn_xTe₂ and Bi_1.99Cr_0.01Te₃, for which Kondo-type interaction between magnetic moments and carriers prevails. In contrast, spin glass CuCrTiS₄ exhibits negative MTEP like in ferromagnetic ruthenates and paramagnetic misfit cobaltites. This investigation of some chalcogenides and oxides provides key ingredients to select magnetic materials for which S benefits from spin entropy.

摘要

电荷和自旋之间的相互作用可能会影响载流子的动力学并决定它们的热电特性。在这方面，磁热电功率 MTEP，即在外部磁场的应用下测量塞贝克系数S，是揭示磁矩对S的作用的有力技术。这可以通过不同的过渡金属硫族化物来说明：CuCrTiS ₄和 CuMnTiS ₄磁性硫尖晶石，与磁性氧化物、居里-魏斯 (CW) 顺磁性错配钴酸盐、钌酸盐、铁磁性钙钛矿或泡利顺磁四重钙钛矿和 CuGa _{1- x 进行比较}锰_x碲₂黄铜矿碲化物和 Bi _1.99 Cr _0.01 Te ₃其中分别由 3%-Mn 和 1%-Cr 取代引起的稀磁。在铁磁体（低于 T _C）和 CW 顺磁材料的情况下，当施加磁场时，在低 T 下磁化强度的增加伴随着载流子熵的减少，因此$\left|秒\right|$减少。这与泡利顺磁四重钙钛矿中缺乏 MTEP 是一致的。此外，在 CuGa _{1- x} Mn _x Te ₂和 Bi _1.99 Cr _0.01 Te _{3 中}没有观察到显着的 MTEP ，其中磁矩和载流子之间的 Kondo 型相互作用占优势。相比之下，自旋玻璃 CuCrTiS ₄表现出负 MTEP，就像在铁磁钌酸盐和顺磁错配钴酸盐中一样。对一些硫属元素化物和氧化物的研究为选择S受益于自旋熵的磁性材料提供了关键成分。