Angster David, Dannegger Tobias, Schlegel Julius, Evers Martin, Nowak Ulrich
Fachbereich Physik, Universität Konstanz, D-78457, Konstanz, Germany.
Sci Rep. 2025 Jul 1;15(1):21543. doi: 10.1038/s41598-025-08746-0.
The Landau-Lifshitz-Gilbert (LLG) equation is well-established to describe the spin dynamics of magnetic materials. This first-order differential equation is based on the assumption that the spin angular momenta and corresponding magnetic moments are always parallel. While this assumption is largely unproblematic, both theoretical considerations and experimental results have indicated that the two may become separated on ultrafast timescales, giving rise to inertial dynamics along with a modified spin wave dispersion. Here, we apply linear spin wave theory to the inertial LLG equation to compute the eigenmodes of the altermagnetic materials SmErFeO and α-FeO. We find the largest influence of nutation on the magnetic resonances in the case of hematite, which exhibits both a sizeable shift of the resonance frequencies as compared to the inertia-free case and additional nutational resonances that are in a similar order of magnitude to the materials' higher-frequency precessional exchange modes. While the realistic magnitude of the inertial parameter remains an open question, we hope that our quantitative analysis provides the starting point for further experimental investigations.
朗道-栗弗席兹-吉尔伯特（LLG）方程已被广泛用于描述磁性材料的自旋动力学。这个一阶微分方程基于自旋角动量和相应磁矩始终平行的假设。虽然这个假设在很大程度上没有问题，但理论考量和实验结果都表明，在超快时间尺度上，两者可能会分离，从而产生惯性动力学以及修正的自旋波色散。在此，我们将线性自旋波理论应用于惯性LLG方程，以计算交替磁性材料SmErFeO和α-FeO的本征模。我们发现，在赤铁矿的情况下，章动对磁共振的影响最大，与无惯性情况相比，其共振频率有相当大的偏移，并且还有额外的章动共振，其量级与材料的高频进动交换模式相似。虽然惯性参数的实际大小仍然是一个悬而未决的问题，但我们希望我们的定量分析能为进一步的实验研究提供起点。
