Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
Inorg Chem. 2012 Jun 18;51(12):6890-7. doi: 10.1021/ic300685d. Epub 2012 Jun 5.
The spin reorientation (SR) phenomenon of the square-lattice antiferromagnets RMnAsO (R = Ce, Nd) was investigated by analyzing the spin-exchange interactions between the rare-earth and the transition-metal ions (R(3+) and Mn(2+), respectively) on the basis of density functional calculations. It is found that the symmetry and strength of the Dzyaloshinskii-Moriya (DM) interaction are determined primarily by the partially filled 4f states of the R(3+) ions and that the DM and biquadratic (BQ) exchanges between the R(3+) and the Mn(2+) ions are unusually strong and control the observed spin reorientation phenomenon. Below their SR temperature, the Mn(2+) and Ce(3+) moments are orthogonal in CeMnAsO but are collinear in NdMnAsO, because the DM interaction dominates over the BQ interaction for CeMnAsO, while the opposite is the case for NdMnAsO. Experiments designed to test the implications of our findings are proposed.
基于密度泛函计算，通过分析稀土离子（分别为 R(3+)和 Mn(2+)）与过渡金属离子之间的自旋交换相互作用，研究了四方晶格反铁磁体 RMnAsO（R = Ce，Nd）的自旋重取向（SR）现象。结果表明，Dzyaloshinskii-Moriya（DM）相互作用的对称性和强度主要由 R(3+)离子的部分填充 4f 态决定，并且 R(3+)和 Mn(2+)离子之间的 DM 和双二次（BQ）交换非常强，控制着观察到的自旋重取向现象。在它们的 SR 温度以下，CeMnAsO 中 Mn(2+)和 Ce(3+)磁矩是正交的，而在 NdMnAsO 中则是共线的，因为 DM 相互作用在 CeMnAsO 中占主导地位，而在 NdMnAsO 中则相反。提出了设计实验来检验我们发现的影响。
