Nonlinear magnetization dynamics of antiferromagnetic spin resonance   induced by intense terahertz magnetic field
  We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced by a strong terahertz magnetic field resonantly enhanced with a split ring resonator and measured with magneto-optical Kerr effect microscopy. The terahertz magnetic field induces a large change (~40%) in the spontaneous magnetization. The frequency of the antiferromagnetic resonance decreases in proportion to the square of the magnetization change. A modified Landau-Lifshitz-Gilbert equation with a phenomenological nonlinear damping term quantitatively reproduced the nonlinear dynamics. 
Y Mukai, H Hirori, T Yamamoto, H Kageyama, K Tanaka
physics.optics cond-mat.mes-hall