Nanocrystalline Nickel-Substituted Lanthanum Cobaltites Synthesized by Urea Combustion Method: Magnetic and Transport Properties
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We have systematically investigated the effect of Ni substitution on the structural, magnetic and transport properties of LaCoO3. Single-phase rhombohedral structure with space group R-3c is confirmed by the Rietveld refinement of X-ray diffraction data in all samples. The unit cell parameters were found to increase with Ni doping. The FM and AFM were observed to coexist as confirmed by M–H hysteresis. Positive values of Θ for nickel-doped samples are consistent with the existence of FM interactions. The effective magnetic moment decreases with Ni substitution. All the samples exhibit temperaturedependent semiconducting behaviour. The electrical resistivity decreases considerably with increasing Ni content and with increasing temperature. The transport mechanism has been investigated by fitting a nearest-neighbour small polaron hopping (SPH) model.
KeywordsCombustion method Crystal structure Magnetic properties Transport properties
The authors are also thankful to Dr. Harpreet Singh, Central Research Facility Section, Indian Institute of Technology Ropar, for recording the XRD. Thanks are also due to Prof. Ramesh Chandra, Institute Instrumentation Centre, Indian Institute of Technology, Roorkee, for recording the TEM. We are also thankful to the Director of Central Instruments Facility, Indian Institute of Technology, Guwahati, for carrying out the M–H magnetic measurements.
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