Novel Magnetic Phases Revealed by Ultra-High Magnetic Field in the Frustrated Magnet ZnCr_2O_4
Novel Magnetic Phases Revealed by Ultra-High Magnetic Field in the Frustrated Magnet ZnCr_2O_4
复制标题
受挫磁体ZnCr_2O_4中超高磁场揭示的新磁相
DOI：
10.1143/jpsj.81.114701
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发表时间：
2012
影响因子：
1.7
通讯作者：
S. Takeyama
中科院分区：
文献类型：
--
作者：
A. Miyata;H. Ueda;Y. Ueda;Y. Motome;N. Shannon;K. Penc;S. Takeyama
对尖晶石氧化物ZnCr2O4进行了法拉第旋转和磁光吸收光谱测量，这是一个三维几何受阻磁体的原型。测量是在温度低至4.6K，高达600T的超强磁场下进行的。超强磁场是由电磁通量压缩方法产生的。我们得到了在400T以上发生相变的完全极化相的精确磁化曲线。实验磁化曲线与蒙特卡罗计算的结果进行了比较，该模型考虑了自旋-晶格耦合直到完全饱和磁化。利用Cr3+离子d带内跃迁的吸收光谱峰以及激子-磁振子-声子跃迁来监测在强磁场作用下的晶体结构和磁结构。在全极化相之前发现了一种新的磁相，通过350T附近磁吸收强度的变化得到了澄清，伞状磁结构被认为是最可能的新相。基于对称性破缺的相似性，讨论了ZnCr2O4的磁结构与4He的量子相之间的物理类比。
Faraday rotation and magneto-optical absorption spectral measurements were conducted on a spinel oxide, ZnCr2O4, a prototype of three-dimensional geometrically frustrated magnet. The measurements were carried out at temperatures down to 4.6 K under ultra-high magnetic fields of up to 600 T. The ultra-high magnetic fields were generated by the electro-magnetic flux compression method. We obtained a precise magnetization curve up to a fully polarized phase, where the phase transition takes place above 400 T. The experimental magnetization curves were compared with those obtained by Monte Carlo calculations with an effective spin model including spin–lattice coupling up to fully saturated magnetization. The absorption spectral peaks of the intra-d-band transitions in Cr3+ions as well as the exciton–magnon–phonon transition were used for monitoring the crystal and magnetic structures subjected to a strong external magnetic field. A novel magnetic phase was found prior to the fully polarized phase, which was clarified by the change in magneto-absorption intensity around 350 T. An umbrella-like magnetic structure was proposed to be the most plausible candidate for the novel phase. A physical analogy between the magnetic structures of ZnCr2O4and the quantum phases of4He was discussed based on the similarity of symmetry breaking.