YIG和BCVIG中铁磁共振线宽各向异性的可能起因

由于磁弹耦合,应力等效为各向异性场并对磁化强度分布发生影响。借助这一机制阐明了机械抛光的YIG和BCVIG单晶球铁磁共振线宽的各向异性行为,指明机械抛光造成的表面损伤层引起的应力通过磁致伸缩的各向异性使弛豫时间各方向不同,即产生了线宽的各向异性。若损伤层主要由位错组成,按微磁学理论和双磁振子散射模型可得到位错密度、磁致伸缩、磁化强度等与线宽的关系。从测量到的线宽各向异性估算了3μm抛光的YIG的表面层位错密度为5.4×10¹⁰/cm²。该弛豫机制表明,进一步降低多晶小线宽材料的线宽,减小磁致伸缩系数可能是有效途径。 关键词：

POSSIBLE ORIGIN OF THE FMR LINEWIDTH ANISOTROPIES IN YIG AND BCVIG SINGLE CRYSTALS

We propose a possible origin of FME linewidth anisotropy shown in mechanically polished YIG and BCVIG single crystals. The stresses left on the surface of the spheres of these crystals couple with the magnetization through the magnetostriction effect, and thus give rise to an additional linewidth, which is anisotropic due to the anisotropic magnetostrictive constant. Supposing that the damaged layer is mainly composed of high density dislocations, a relation between the FME linewidth anisotropy and the magnetostriction constants is deduced based on micromagnetism theory and the two-magnon scattering process. From the measured linewidth anisotropy of YIG, we evaluated the dislocation density of the surface layer to be 5.4×10¹⁰/cm².This relaxation process shows that in order to further reduce the linewidth of an ultra-low linewidth polycrystalline material, suppressing the magnetostriction constant may play an important role.