from THz Spectroscopy Study*

In YFeO₃ iron spins S=5/2 arrange in an antiferromagnetic (AFM) canted state Γ4(G_a,F_c,A_b) well above room temperature. With four spins per unit cell, its spin structure is described by a combination of exchange interactions, Dzyaloshinskii-Moriya (DM) interactions, and single-ion anisotropies (SIA). Since only Fe ions have the non-zero magnetic moment, this compound is a perfect modelling system for spin interactions and a step towards understanding more complex materials, possibly those with multiferroic properties.
We measured absorption of THz radiation in single crystals at the temperature 3 K in magnetic fields up to B = 17 T. THz spectroscopy can measure two out of four spin wave (SW) modes in YFeO₃, those with zero-field energies 1.2 and 2.4 meV. Combining the B dependence of the SW modes with earlier inelastic neutron scattering results, we were able to quantify the parameters of DM interactions and SIA more precisely than was previously possible. We then evaluated different models of the spin structure and determined the one that represents magnetic interactions most accurately.