Evidence of disorder induced magnetic spin glass phase in Sr2FeMoO6 double perovskite

The present work described the disorder induced magnetic properties of Sr2FeMoO6 (SFMO) samples. The crystal structure and magnetic order of SFMO samples with nanosized grains were studied using x-ray diffraction spectrum, scanning electron microscope morphology, and magnetic measurements. Thermal annealing of as prepared chemical routed materials showed an increase in grain size and in the magnetic moment per formula unit. A small decrease in magnetic moment was noted at higher annealing temperature. At the same time, the ac susceptibility measurement indicated the presence of a magnetic spin glass phase in the material, coexisting with the ferromagnetic matrix. The observation of the magnetic glassy phase confirmed the presence of intrinsic disorder in the lattice structure of SFMO. The signature of intrinsic disorder in the samples, irrespective of annealing temperatures, is also realized from the splitting of temperature dependent field cooled and zero field cooled magnetization curves. Such magnetic splitting in the temperature dependence of magnetization curves is suppressed at a higher magnetic field. A careful analysis of the temperature and field dependent magnetization data provided more insight on the grain size dependent disorder in the double perovskite structure. (C) 2009 American Institute of Physics. [doi:10.1063/1.3236566]