Magnetic, transport, thermal properties and orbital state for spinel MnTi₂O₄

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• 作者：Yuanjie Huang^a ; Zhaorong Yang^b ; ^{zryang@issp.ac.cn} ; Yuheng Zhang^a
• 关键词：Short-ranged orbital ordering ; Jahn&ndash ; Teller effect ; Spin&ndash ; orbit coupling
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2012
• 期刊代码：31_03048853
• 类别：ph
• 出版时间：July, 2012
• 卷：324
• 期：13
• 页码：2075-2081
• 文件大小：773 K

摘要

We systematically investigated the various properties of MnTi₂O₄. The compounds are found to be conducted by small polarons with different activation energies across the temperature T₁ and deviate from the Curie-Weiss law for the magnetic susceptibility at T₁. Also at T₁ do the specific heat undergo a crossover. As indicated by the X-ray diffraction peaks, the series of phenomena near the characteristic temperature T₁ are attributed to the happening of the micro-structural distortion, and the distortion implies the short-range orbital ordering state below T₁. This short-range oribtal ordering state is supported by the little upturn of the thermal conductance at T₁. As the temperature decreases, the systems enter a long-ranged collinear ferrimagnetic state at a lower temperature T_N. Moreover, the compounds decreases in thermal-electric power with the decrease of temperature and undergoes a p-type to n-type transition at the temperature T_pn. Through the quantitative theoretical analysis, both the decrease of the thermal power and the p-type to n-type transition are cooperatively induced by spin-orbit (SO) coupling and the Jahn-Teller (JT) effect.