Polarization Effect in Electron Paramagnetic Resonance with Anisotropic Effective G-Tensor and Anisotropic Spin Relaxation

Applied Magnetic Resonance. 2022. Vol. 53. No. 11. P. 1505–1516.

Demishev S. V., Semeno A. V.

A simple semi-classical model of magnetization dynamics based on Landau-Lifshits equation of motion with anisotropic effective g-tensor and anisotropic spin relaxation is proposed and applied to the case of electron paramagnetic resonance (EPR). In the Faraday geometry, the model predicts polarization effect consisting in strong dependence of the EPR line shape and magnitude on orientation of vector h of oscillating magnetization with respect to the crystal structure, so that EPR may be suppressed for some directions of h. The EPR with anisotropic parameters possesses specific magnetic oscillations, which are different from standard circular rotation of the magnetization vector around the direction of external magnetic field. In general case the trajectory of the magnetization vector end is either elongated quasi-ellipse, the position of the main axis of which depends on the magnitude of the external magnetic field, or magnetic oscillations may acquire almost linear character. The model is successfully applied for the quantitative accounting of the polarization effect for EPR mode observed in CuGeO3 doped with 2% of Co impurity, which remained unexplained for more than 15 years.

Keywords: electron paramagnetic resonance, Anisotropic g-tensor, Anisotropic spin relaxation, Cobalt impurity, Polarization effect, CuGeO3