Eur. Phys. J. B 20, 165-175 (2001)
https://doi.org/10.1007/s100510170266

Quantum theory of the magneto-optical effect and magnetization of Nd-substituted yttrium iron garnet

¹ Department of Physics, Luoyang Teacher's College, Luoyang 471022, PR China
² China Center of Advanced Science and Technology (World Laboratory), PO Box 8730, Beijing 100080, China and Department of Physics, Nanjing University, Nanjing 210008, PR China
³ China Center of Advanced Science and Technology (World Laboratory), PO Box 8730, Beijing 100080, China and Department of Physics, Luoyang Teacher's College, Luoyang 471022, PR China
⁴ Laboratoire des Champs Magnetiques Intenses, CNRS/MPI, BP 166, 38042 Grenoble, France

Corresponding author: ^a mguillot@labs.polycnrs-gre.fr

Received: 8 November 2000
Published online: 15 March 2001

Abstract

The magneto-optical and magnetic properties of Nd ions in YFeO garnet are analyzed by using quantum theory. In the spontaneous state, the magneto-optical effects originate mainly from the intra-ionic electric dipole transitions between the 4 and 4 states split by the spin-orbit, crystal field, and superexchange interactions. For the excited configuration, the coupling scheme of Yanase is extended to the Nd ion. The magneto-optical resonance frequencies are mainly determined by the splitting of the 5d states induced by the crystal field. The theoretical results of both Nd magnetization and Faraday rotation are in good agreement with experiments. The observed Faraday rotation is proved to be of the paramagnetic type. Although the value of the magneto-optical resonance frequency derived from a macroscopic analysis is approximately confirmed by our theoretical study, a new assignment about the transitions associated with this resonance is unambiguously determined. The spin-orbit coupling of the ground configuration has a great influence on both the Faraday rotation and magnetization, but, unlike the theoretical results obtained in some metals and alloys, the relation between the Faraday rotation and the spin-orbit coupling strength is more complex than a linear one. The magnitude of the magneto-optical coefficient increases as the spin-orbit interaction strength of the ground configuration decreases when the strength is not very weak. Finally, the temperature dependence of the magneto-optical coefficient and the effect of the mixing of different ground-term multiplets induced by the crystal field are analyzed.