Symmetry breaking induced magnon-magnon coupling in synthetic antiferromagnets
Symmetry breaking induced magnon-magnon coupling in synthetic antiferromagnets
复制标题
合成反铁磁体中对称破缺引起的磁振子-磁振子耦合
DOI：
10.1103/physrevb.103.064429
复制
发表时间：
2021-02-22
影响因子：
3.7
通讯作者：
He, Wei
中科院分区：
文献类型：
--
作者：
Li, Mei;Lu, Jie;He, Wei
提出了对称破缺合成反铁磁体微波吸收光谱的一般理论。通常情况下，SAF的两个铁磁性子层的不均匀或不同厚度导致内部对称性破缺，而直流磁场的离面分量导致外部对称性破缺。SAFS的破缺对称性排除了具有相反宇称的纯同相和异相共振模之间的原始对称性保护的交叉。另一方面，由于对称性破缺引起的磁振子-磁振子耦合，新的频率分支成为原始裸模的杂化，从而导致铁磁共振频率的间接间隙。给出了几种典型情况下的能隙宽度与对称性破缺程度的关系，并与已有的实验结果进行了比较。我们的理论提供了对不对称SAF丰富的铁磁共振光谱结构的简单而物理的理解。
We propose a general theory of microwave absorption spectroscopy for symmetry-breaking synthetic antiferromagnets (SAFs). Generally, inhomogeneity or different thickness of the two ferromagnetic sublayers of a SAF results in the intrinsic symmetry breaking, while out-of-plane components of dc magnetic fields lead to the extrinsic one. The broken symmetry of SAFs excludes the original symmetry-protected crossing between pure in-phase and out-of-phase resonance modes with opposite parity. Alternatively, new frequency branches become hybridization of original bare modes in terms of symmetry-breaking-induced magnon-magnon coupling, which results in an indirect gap in ferromagnetic resonance frequencies. Also, the dependence of gap width on the degree of symmetry breaking for several typical cases are presented and compared with existing experiments. Our theory provides a simple but physical understanding on the rich structure of ferromagnetic resonance spectra for asymmetric SAFs.