Magnetic and magneto-optical properties of neodymium gallium garnet under “extreme” conditions

Abstract

The magnetization and Faraday rotation (FR) of Nd3 Ga5 O12 (NdGaG) were studied under high magnetic fields up to 33 T and low temperatures down to 4.2 K. No saturation of the magnetization was observed. The magnetic moment of the fundamental doublet was determined to be close to 1.25 μB/ion, with the energy gap with respect to the nearest level of about 132 cm−1. Above 30 K, the magnetic moment, M(H), shows a linear field dependence, even at the maximum field. The reciprocal magnetic susceptibility follows the Curie–Weiss law at temperatures above 100 K, with a Curie constant of about 15% below that of free ions. At 4.2 K, the FR spectrum is strongly field dependent, with very strong signals in the wavelength range from 440 to 720 nm. The FR signal decreases rapidly with increasing wavelengths above 720 nm and retains very small values in the wavelength range from 800 to 850 nm. The results are briefly discussed in light of a recent theoretical analysis of the magnetic and FR properties of the isomorphous ferrimagnetic garnet (Nd:YIG).