梯度修正磁振子色散的一条捷径：仅交换情形
A shortcut to gradient-corrected magnon dispersion: exchange-only case
摘要：
铁磁材料中磁振子色散的从头计算通常依赖于绝热局域密度近似（ALDA），其中有效的交换相关场处处平行于磁化强度。然而，这些计算往往高估了“磁振子刚度”，定义为在零波矢量处评估的磁振子频率与波矢量关系的曲率。在这里，我们提出了一个简单的程序，以改善磁振子色散考虑到梯度修正的ALDA在交换只的水平。我们发现，这种梯度校正总是降低磁振子刚度。令人惊讶的大尺寸的这些修正（$\sim 30\%$）大大提高了钴和镍的计算和观察到的磁振子刚度之间的一致性，这是已知的被高估的ALDA。
英文摘要：
Ab initio calculations of the magnon dispersion in ferromagnetic materials typically rely on the adiabatic local density approximation (ALDA) in which the effective exchange-correlation field is everywhere parallel to the magnetization. These calculations, however, tend to overestimate the "magnon stiffness", defined as the curvature of the magnon frequency vs. wave vector relation evaluated at zero wave vector. Here we suggest a simple procedure to improve the magnon dispersion by taking into account gradient corrections to the ALDA at the exchange-only level. We find that this gradient correction always reduces the magnon stiffness. The surprisingly large size of these corrections ($\sim 30\%$) greatly improves the agreement between the calculated and the observed magnon stiffness for cobalt and nickel, which are known to be overestimated within the ALDA.
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