The effect of NiO doping on the structure, magnetic and magnetotransport properties of La0.8Sr0.2MnO3 composite

The effect of NiO doping on the structure, magnetic and magnetotransport properties of La0.8Sr0.2MnO3 (LSMO)/xNiO has been investigated. These studies show that some part of the NiO goes into the perovskite lattice substituting Mn in LSMO and remainder segregates as a separate phase at the grain boundaries and grain surfaces. The presence of NiO at the grain boundaries increases the disordered states at the surface of the grains and therefore the low temperature resistivity increases very quickly by the increase of NiO doping level. Results also show that the NiO doping has an effect on a LFMR. The value of MR increases for low doping level of 0 <= x <= 3 and decreases at high doping level of x >= 5. The spin dependent tunneling and scattering at the interfaces of the grain boundaries are responsible for the increasing of LFMR at x <= 3, while reduction of LFMR at x >= 5 originates from substitution of Ni2+ for the Mn3+ ions introduces the magnetic dilution into the samples. (c) 2006 Elsevier B.V. All rights reserved.