Spin singlet formation in MgTi2O4:: Evidence of a helical dimerization pattern -: art. no. 056402
Spin singlet formation in MgTi2O4:: Evidence of a helical dimerization pattern -: art. no. 056402
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DOI：
10.1103/physrevlett.92.056402
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发表时间：
2004-02-06
影响因子：
8.6
通讯作者：
Cheong, SW
中科院分区：
文献类型：
--
作者：
Schmidt, M;Ratcliff, W;Cheong, SW
过渡金属尖晶石MgTi₂O₄在冷却到低于Tₘ₋ᵢ = 260 K时会发生金属 - 绝缘体（M - I）转变。在Tₘ₋ᵢ以下，磁化率急剧降低，这表明磁性单态开始出现。利用高分辨率同步辐射和中子粉末衍射，我们解析了MgTi₂O₄的低温晶体结构，发现其中包含具有短Ti - Ti距离（自旋单态的位置）的二聚体，它们与长键交替形成螺旋结构。基于杂化交换密度泛函理论的能带结构计算表明，在低温下，MgTi₂O₄是一种轨道有序的能带绝缘体。
The transition-metal spinel MgTi2O4 undergoes a metal-insulator (M-I) transition on cooling below TM-I=260 K. A sharp reduction of the magnetic susceptibility below TM-I suggests the onset of a magnetic singlet state. Using high-resolution synchrotron and neutron powder diffraction, we have solved the low-temperature crystal structure of MgTi2O4, which is found to contain dimers with short Ti-Ti distances (the locations of the spin singlets) alternating with long bonds to form helices. Band structure calculations based on hybrid exchange density functional theory show that, at low temperatures, MgTi2O4 is an orbitally ordered band insulator.