Effect of particle size on electrical and magnetotransport properties of manganite nanoparticles

A systematic study of the particle size effect on electrical, magnetic and colossal magnetoresistance of nanocrystalline Nd_0.7Sr_0.3MnO₃ sample was carried out. Samples were synthesised by citrate auto-ignition method. The resulting precursors were then calcined for 3 h at 700, 800 and 900°C to get different particle sizes. To measure electrical resistivity and magnetoresistance, pellets were sintered and quenched to room temperature for 10 minutes at respective calcination temperature. X-ray diffraction patterns, Debye-Scherrer´s formula, and transmission electron microscopy were used to approximate crystallite sizes. AC magnetic susceptibility shows a broad transition, due to particle size reduction, with ferromagnetic transition temperature at 130 K. Upon cooling, the electrical resistivity shows an insulator to metal transition at ∼140 K. It is also observed that spin moment values increase with increasing particle size.