We measured the temperature dependences of the static magnetization and the spin excitation in the square-lattice multiferroic ${\mathrm{Ba}}_2{\mathrm{MnGe}}_2{\mathrm{O}}_7$. An anisotropy gap of the observed low-energy mode is scaled by electric polarization rather than a power of the sublattice moment. Spin-nematic interaction in the effective spin Hamiltonian, which is equivalent to interaction of the electric polarization, is responsible for the easy-axis anisotropy. The nontrivial behavior of the anisotropy gap can be rationalized as change in the hybridized $d\text{−}p$ orbital with temperature, leading to the temperature dependence of the spin-nematic interaction.

中文翻译：

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多铁性 Ba2MnGe2O7 中磁各向异性的非平凡温度依赖性

我们测量了方形晶格多铁性中静态磁化强度和自旋激发的温度依赖性 ${巴}_2{\mathrm{锰锗}}_2{\mathrm{哦}}_7$. 观察到的低能量模式的各向异性间隙是由电极化而不是亚晶格矩的功率来缩放的。有效自旋哈密顿量中的自旋-向列相互作用，相当于电极化的相互作用，是易轴各向异性的原因。各向异性间隙的非平凡行为可以合理化为杂化的变化$d\text{-}磷$ 轨道与温度，导致自旋-向列相互作用的温度依赖性。