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arXiv 1004.0839cond-mat.str-el
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高温下S=1/2反铁磁体的电子自旋共振

Electron spin resonance in S=1/2 antiferromagnets at high temperature

S. El Shawish, O. Cepas, S. Miyashita

摘要:

我们研究了低维自旋系统在高温下的电子自旋共振(ESR),并检验了Kubo-Tomita交换窄化理论。在有限尺寸系统(分子磁体)中,我们发现了一个双峰共振,这与通常的洛伦兹函数有很大的不同。对于无限系统,我们预测的线宽和线型作为各向异性强度的函数。为此,我们使用了一个非微扰计算的记忆功能在短时间(精确对角化)和流体动力学自旋扩散在长时间之间的插值。我们发现,Dzyaloshinskiii-Moriya各向异性一般诱导一个更大的线宽比交换各向异性在二维,相反的一维情况下。

英文摘要:

We study the electron spin resonance (ESR) of low-dimensional spin systems at high temperature, and test the Kubo-Tomita theory of exchange narrowing. In finite-size systems (molecular magnets), we found a double-peak resonance which strongly differs from the usual Lorentzian. For infinite systems, we have predictions for the linewidth and lineshape as a function of the anisotropy strength. For this, we have used an interpolation between a non-perturbative calculation of the memory function at short times (exact diagonalization) and the hydrodynamic spin-diffusion at long times. We show that the Dzyaloshinskii-Moriya anisotropies generally induce a much larger linewidth than the exchange anisotropies in two dimensions, contrary to the one-dimensional case.

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