The behavior of iron in valence states of Fe4+ and Fe2+ has been investigated by measurements of the angular and temperature dependence of the FMR resonance field and linewidth at 9.2 GHz from 4.2 to 295 K on (111) oriented Ca0.142 + Fe4+:YIG and Ge0.104 + Fe2+: YIG epitaxial garnet films. At low temperatures a substantial increase of the first and second order cubic anisotropy energy has been observed, with K1>0 and K2<0 for Fe2+and K1<0, K2>0 for Fe4+containing garnets. However, the magnitude of K1and K2 is much smaller than predicted. In Ca:YIG a change in sign of dK/dT is observed at T<30 K. Anisotropic FMR linewidth maxima below 50 K for Ca:YIG and Ge:YIG and at 180 K for Ca:YIG have been measured and identified with level splitting and charge transfer processes.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering