High-resolution optical spectroscopy and modeling of spectral and magnetic properties of multiferroic ErFe<inf>3</inf>(BO<inf>3</inf>)4

© 2020 American Physical Society. We carried out the high-resolution broadband temperature-dependent polarized optical spectroscopy and theoretical studies of ErFe3(BO3)4 single crystals in the paramagnetic and antiferromagnetic (T<TN=39K) phases. On the basis of the experimentally determined 45 crystal-field (CF) levels of Er3+ ions at sites with the C2 point symmetry, CF calculations were performed, a set of physically grounded CF parameters was obtained and used to model the temperature dependences of the Er magnetic moments measured in neutron-scattering experiments, as well as the magnetic susceptibility and magnetization of the compound; the contributions of the quasi-one-dimensional iron magnetic subsystem were calculated in the frame of the previously developed self-consistent four-particle cluster model. The modeling strongly supports an easy-plane collinear structure of iron magnetic moments and excludes earlier proposed additional magnetic phase