Optical Measurements in Erbium Iron and Erbium Gallium Garnet

Abstract

Optical absorption spectra of erbium iron garnet (ErIG) have been measured at 4.2°, 20°, and 62°K with external magnetic fields up to 25 kOe. From these measurements, the magnetic moment of the groundstate for the two magnetically inequivalent sites can be deduced as μ1=7.0 μB and μ2=4.6 μB yielding an average moment of μ=5.4 μB in the [100]-direction. In addition, we have measured the G-tensor of one excited state (4I9/2) as Gx=(10.0±0.5) cm−1, Gy=(15.0±0.5) cm−1, and Gz=(10.0±0.5) cm−1. The comparison with the g-tensor of this state in the gallium garnet (gx=3.1, gy=3.1, gz=3.9) shows a large anisotropic exchange. Crystal-field energy levels and g-factors of erbium gallium garnet and erbium aluminium garnet have been measured and a good fit to a set of nine crystal-field parameters Akq〈rk〉 has been obtained.