Open Access

Dávid Szaller, Vilmos Kocsis, Sándor Bordács, Titusz Fehér, Toomas Rõõm, Urmas Nagel, Hans Engelkamp, Kenya Ohgushi, István Kézsmárki

• Low-energy magnetic excitations of the easy-axis antiferromagnet TbFe3(BO3)4 are investigated by far-infrared absorption and reflection spectroscopy in high magnetic fields up to 30 T. The observed field dependence of the resonance frequencies and the magnetization are reproduced by a mean-field spin model for magnetic fields applied both along and perpendicular to the easy axis. Based on this model we determined the full set of magnetic interactions, including Fe-Fe and Fe-Tb exchange interactions, single-ion anisotropy for Tb ions and g factors, which describe the ground-state spin texture and the low-energy spin excitations of TbFe3(BO3)4. Compared to earlier studies, we allow a small canting of the nearly Ising-type Tb moments to achieve a quantitative agreement with the magnetic susceptibility measurements. The additional high-energy magnetic resonance lines observed, besides the two resonances expected for a two-sublattice antiferromagnet, suggest a more complex six-sublatticeLow-energy magnetic excitations of the easy-axis antiferromagnet TbFe3(BO3)4 are investigated by far-infrared absorption and reflection spectroscopy in high magnetic fields up to 30 T. The observed field dependence of the resonance frequencies and the magnetization are reproduced by a mean-field spin model for magnetic fields applied both along and perpendicular to the easy axis. Based on this model we determined the full set of magnetic interactions, including Fe-Fe and Fe-Tb exchange interactions, single-ion anisotropy for Tb ions and g factors, which describe the ground-state spin texture and the low-energy spin excitations of TbFe3(BO3)4. Compared to earlier studies, we allow a small canting of the nearly Ising-type Tb moments to achieve a quantitative agreement with the magnetic susceptibility measurements. The additional high-energy magnetic resonance lines observed, besides the two resonances expected for a two-sublattice antiferromagnet, suggest a more complex six-sublattice magnetic ground state for TbFe3(BO3)4.…