Light-Induced Increase in Domain-Wall Stiffness in Si-Doped YIG

Abstract

The initial susceptibility of Si‐doped YIG is reduced by irradiation with light. This effect is explained by a simple two‐center model, a strongly anisotropic center being formed from a less anisotropic one by light‐induced electron transfer. Domain walls are pinned by these strongly anisotropic centers, of density n. If n is small enough, the stiffness will be proportional to n, since by local wall deformations each center within the wall can be made to occupy a site of lowest energy. For larger n this is no longer possible: instead, the optimum wall position will be determined by the statistical fluctuations of the center distribution, and the stiffness will be proportional to n^1/2.