Ferromagnetic resonance studies on colossal magnetoresistance films: Effects of homogeneity and light illumination

摘要

Ferromagnetic resonance (FMR) in the dependence on magnetic field orientation, and effect of the laser light on the magnetic ordering were studied in colossal magnetoresistance films, La_(1-x)Sr_xMnO_3 and La_(1-x)Ba_xMnO_3. The FMR linewidth increased with the decrease in temperature in La_(1-x)Sr_xMnO_3 films, and was nearly temperature independent in La_(1-x)Ba_xMnO_3, that was attributed to the different degree of magnetic homogeneity of the films. Layered structures La_(1-x)Ba_xMnO_3 on silicon with intermediate layer of SrTiO_3 were characterized by FMR as highly homogeneous. From the orientation and temperature dependences of the FMR spectra, the effective magnetization, and effective anisotropy fields were estimated. The laser light illumination resulted in the change of FMR line shape and intensity, and was interpreted in terms of optically induced magnetic disordering and effective heating of the spin system.