钆镓石榴石中的无色散自旋波
Dispersionless spin waves in Gadolinium Gallium Garnet
摘要：
本文报道了中子在高磁场下在Gd_3Ga_5O_（12）粉末样品上的散射结果。我们发现，在高场（B> 1.8T）下，系统不是完全极化的，但偶极相互作用引起的磁矩有一个小的倾斜。我们表明，倾斜的程度是准确预测的标准哈密顿量，其中包括偶极相互作用。非弹性散射在大动量转移时由几乎无色散的激发带主导。我们表明，这些对应于本地化的自旋波的10个网站环，预期由最近邻相互作用所描述的系统，并在高场B>1.8 T的频谱是很好地描述了自旋波理论。磁场<1.8 T时的相位特征为在（210）处的反铁磁布拉格峰和无公度峰。
英文摘要：
We report the results of neutron scattering on a powder sample of Gd3Ga5O12 at high magnetic fields. We find that in high fields (B>1.8 T) the system is not fully polarized, but has a small canting of the moments induced by the dipolar interaction. We show that the degree of canting is accurately predicted by the standard Hamiltonian which includes the dipolar interaction. The inelastic scattering is dominated at large momentum transfers by a band of almost dispersionless excitations. We show that these correspond to the spin waves localized on ten site rings, expected for a system described by a nearest neighbor interaction, and that the spectrum at high fields B>1.8 T is well-described by a spin wave theory. The phase for fields <1.8 T is characterized by an antiferromagnetic Bragg peak at (210) and an incommensurate peak.
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