Spin reorientation transition in Sm0.5Tb0.5FeO3 orthoferrite single crystal

Single crystal of Sm_0.5Tb_0.5FeO₃ was grown by an optical floating zone method. The spin reorientation transition behavior (Γ₂ → Γ₂₄ → Γ₄) is observed in the temperature range from 150 to 250 K. The dynamics of spin reorientation transition is studied by terahertz time-domain spectroscopy (THz-TDS). FM mode was only discovered when temperature is below 55 K. And the FM mode resonant frequency increases from 0.216 THz to 0.268 THz with temperature deceasing from 55 K to 39 K. The AFM mode resonant frequency is fixed at 0.542 THz except in the very low temperature range. Our results demonstrate that THz-TDS is an effective means to study the dynamical iron ions SRT in RFeO₃.