Using inelastic neutron scattering, we investigate the spin wave excitations on the antiferromagnetic MnTiO₃ (T_N = 65 K), which has the stacked honeycomb structure. At T = 2 K, the spin wave energy extends up to 10.7 meV with the zone-center anisotropy gap of 0.8 meV. Whereas the dispersion is also strong along the direction perpendicular to the honeycomb planes, the exchange cancellation causes the magnetic interactions to be effectively anisotropic below T_N. While the spin wave spectrum survives at temperatures above T_N, we find that the magnetic interactions become more anisotropic within the paramagnetic phase. These results suggest that the magnetic interaction in MnTiO₃ crosses over from being three dimensional to two dimensional above T_N.

中文翻译：

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蜂窝反铁磁体MnTiO3中的自旋波激发

使用非弹性中子散射，我们研究了具有堆叠蜂窝结构的反铁磁MnTiO ₃（T _N = 65 K）上的自旋波激发。在T = 2 K时，自旋波能量扩展到10.7 meV，带中心各向异性间隙为0.8 meV。尽管在垂直于蜂窝平面的方向上色散也很强，但交换抵消导致磁相互作用在T _N以下有效地各向异性。自旋波谱在高于T _N的温度下仍然存在，我们发现顺磁性相中的磁性相互作用变得更加各向异性。这些结果表明，MnTiO ₃中的磁性相互作用在T _N上方从三维跃迁到二维。