Terbium gallium garnet (TGG), Tb3Ga5O12, is well known for its applications in laser optics, but also exhibits complex low-temperature magnetism that is not yet fully understood. Its low-temperature magnetic order is determined by means of time-of-flight neutron powder diffraction. It is found to be a multiaxial antiferromagnet with magnetic Tb3+ ions forming six sublattices of magnetic moments aligned parallel and anti-parallel to the ⟨100⟩ crystallographic directions of the cubic unit cell. The structure displays strong easy-axis anisotropy with respect to a two-fold axis of symmetry in the local orthorhombic environment of the Tb3+ sites. The crystal-field splitting within the single-ion ground-state manifold is investigated by inelastic neutron scattering on powder samples. A strong temperature dependence of the quasidoublet ground-state is observed and revised parameters of the crystal-field Hamiltonian are given. The results of bulk magnetic susceptibility and magnetisation measurements are in good agreement with values based on the crystal-field model down to 20~K, where the onset of magnetic correlations is observed.
@article{arxiv.1910.08570,
title = {Magnetic order and single-ion anisotropy in Tb$_3$Ga$_5$O$_{12}$},
author = {R. Wawrzyńczak and B. Tomasello and P. Manuel and D. Khalyavin and M. D. Le and T. Guidi and A. Cervellino and T. Ziman and M. Boehm and G. J. Nilsen and T. Fennell},
journal= {arXiv preprint arXiv:1910.08570},
year = {2019}
}