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arXiv 0903.2847cond-mat.mtrl-scicond-mat.str-el
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钇铁石榴石薄膜的微观自旋波理论

Microscopic spin-wave theory for yttrium-iron garnet films

Andreas Kreisel, Francesca Sauli, Lorenz Bartosch, Peter Kopietz

摘要:

受最近铁磁绝缘体钇铁石榴石(YIG)薄膜实验的启发,我们发展了一种有效的微观方法来计算这些系统的自旋波谱。我们使用一个有效的量子海森堡模型的铁磁最近邻交换和长程偶极-偶极相互作用的立方晶格上的实验相关的磁振子带的YIG模型。通过Holstein-Primakoff变换和截断在二次阶玻色子的自旋自由度的玻色化后,我们得到的自旋波谱实验相关的参数,而无需进一步近似的数值对角化,使用有效的Ewald求和技术进行偶极求和。我们比较我们的数值结果与两种不同的解析近似和预测的基础上的唯象Landau-Lifshitz方程。

英文摘要:

Motivated by recent experiments on thin films of the ferromagnetic insulator yttrium-iron garnet (YIG), we have developed an efficient microscopic approach to calculate the spin-wave spectra of these systems. We model the experimentally relevant magnon band of YIG using an effective quantum Heisenberg model on a cubic lattice with ferromagnetic nearest neighbor exchange and long-range dipole-dipole interactions. After a bosonization of the spin degrees of freedom via a Holstein-Primakoff transformation and a truncation at quadratic order in the bosons, we obtain the spin-wave spectra for experimentally relevant parameters without further approximation by numerical diagonalization, using efficient Ewald summation techniques to carry out the dipolar sums. We compare our numerical results with two different analytic approximations and with predictions based on the phenomenological Landau-Lifshitz equation.

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