金红石NiF$_2$中的磁二色性：分离交变磁与铁磁效应
Magnetic Dichroism in Rutile NiF$_2$: Separating Altermagnetic and Ferromagnetic Effects
AI总结：
本文通过数值模拟预测NiF₂中XMCD信号，区分交变磁与铁磁贡献，并证明信号可线性分解，为验证Néel矢量与X射线霍尔矢量关系提供方法。
摘要：
我们展示了Ni在弱铁磁交变磁体NiF$_2$中L$_{2,3}$边的X射线磁圆二色性（XMCD）的数值模拟。我们的结果预测，对于垂直于磁矩传播的光，存在显著的XMCD信号，这些磁矩大致沿[100]易轴方向排列。分析表明，XMCD信号中的交变磁和铁磁贡献可以通过它们对外加磁场的依赖性来唯一区分。通过改变磁场相对于易轴的角度，可以系统地控制Néel矢量和净磁化强度的面内取向。我们进一步证明，即使在高达40 T的磁场下，且对于任何面内取向，XMCD信号都可以精确地描述为两个光谱分量的线性组合，其几何前因子由磁场大小和方向决定。这一见解使得对金红石结构中Néel矢量取向与X射线霍尔矢量之间独特关系的实验验证成为可能。支持这些发现的定量模拟已提供。
英文摘要：
We present numerical simulations of x-ray magnetic circular dichroism (XMCD) at the L$_{2,3}$ edge of Ni in the weakly ferromagnetic altermagnet NiF$_2$. Our results predict a significant XMCD signal for light propagating perpendicular to the magnetic moments, which are approximately aligned along the [100] easy-axis direction. The analysis shows that the altermagnetic and ferromagnetic contributions to the XMCD signal can be uniquely distinguished by their dependence on an applied magnetic field. By varying the angle of the field relative to the easy axis, the in-plane orientation of both the Néel vector and the net magnetization can be systematically controlled. We further demonstrate that the XMCD signal, even under fields as strong as 40 T and for any in-plane orientation, can be accurately described as a linear combination of two spectral components, with geometrical prefactors determined by the field magnitude and direction. This insight enables experimental validation of the distinctive relationship between the Néel vector orientation and the x-ray Hall vector in the rutile structure. Quantitative simulations supporting these findings are provided.
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