Synthesis, structure and physical properties of spinel solid solutions Mg₂TiO₄–MgTi₂O₄

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• 作者：Isobe ; Masahiko ; Ueda ; Yutaka
• 关键词：MgTi₂O₄&ndash ; MgTi₂O₄ ; Pyrochlore lattice with S=1/2 ; Spinel solid solutions ; Magnetic susceptibility ; Resistivity
• 刊名：Journal of Alloys and Compounds
• 出版年：2004
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：November 30, 2004
• 卷：383
• 期：1-2
• 页码：85-88
• 文件大小：154 K

摘要

We investigated the preparation condition for stoichiometric MgTi₂O₄ and the electromagnetic properties of the spinel solid solution Mg_2−xTi_1+xO₄ (0≤x≤1). Only a highly reductive sintering atmosphere gives a possibility for the preparation of stoichiometric MgTi₂O₄, based on Ti³⁺. MgTi₂O₄ thus obtained shows a metal to spin singlet insulator transition accompanied by the structural change from cubic to tetragonal. Introduction of Ti³⁺ (d¹, S=1/2) to the non-magnetic insulator Mg₂Ti⁴⁺O₄ acts partly as doping of carrier dopants and partly as a source of localized electrons. Increasing content of Ti³⁺ leads to their delocalization, resulting in the metallic MgTi₂O₄ at x=1.0. The Peierls-like transition observed in the stoichiometric MgTi₂O₄ rapidly smears out with the content of Ti³⁺ ion decrease, suggesting an important role of orbital degree of freedom as an effective mechanism for the transition, which seems to be significantly influenced by the randomness associated with the appearance of Ti⁴⁺ ions.