Effect of microstructure on magnetization processes of La0.7Sr0.3MnO3 perovskite

The magnetization processes involving reversible and irreversible domain wall (DW) displacements as well as domain rotations in La0.7Sr0.3MnO3 (LSMO) perovskite with porosity p ranging from 38.86 to 56.25% have been investigated using complex permeability measurement. At low p, the frequency spectra show two relaxation processes, respectively, corresponding to reversible domain wall displacements and domain rotations. With increasing p up to 56.25%, the spectra display resonance-type dispersion due to domain rotations. Moreover, initial permeability monotonically decreases from 19.61 to 2.10 and can be described using a simplified effective medium theory. The Rayleigh constant eta, characterizing irreversible domain wall motions, decreases with increasing porosity. Upon application of a dc magnetic field H-e, eta initially decreases rapidly, then becomes constant for H-e larger than 1.3 x 10(5) A/m, indicating that mu' mainly arises from the contribution of domain rotations while the domain wall motions are damped. (c) 2005 Elsevier B.V. All rights reserved.