Influence of grain size and grain boundaries on the properties of La0.7Sr0.3CoxMn1−xO3

We have synthesized La0.7Sr0.3Mn0.9Co0.1O3 granular perovskites using ethylenediaminetetraacetic acid (EDTA) as a complexing agent. The influence of grain size and grain boundary structure on the physical properties was investigated. Our results show that decreasing grain size leads to lowering of the ferromagnetic transition temperature, broadening of the transition, decrease in magnetization and enhancement of resistivity and magnetoresistance at low temperatures. Also, electron spin resonance linewidth and g-value will decrease. These results are explained by spin dependent scattering at the grain boundaries and weakening of magnetic interaction near the surface of grains, which reduces the internal field in the system.