Effect of Reduced Dimensionality on the Magnetic and Transport Properties of Ca Doped Colossal Magnetoresistive Nanoparticles

Abstract

Magnetic and electrical measurements of different nanosize Ca doped colossal magnetoresistive La_0.7Ca_0.3MnO₃ are reported. The nanoparticles are synthesized with the modified citrate rout at different temperatures. X-ray diffraction measurements revealed three dominant peaks 23.04⁰, 40.517⁰ .47.17⁰, 58.66⁰ which confirms the perovskite-like structure. The average crystallite size the nanoparticles are found to be 20 to 32nm. All the synthesized nanoparticles exhibit ferromagnetic ordering close to the phase transition temperatures. The size dependent magnetic and electrical transport properties are explored at different fields and temperature. Saturation magnetization is found to decrease with decreasing particle diameter. It is found that the particle size can tune the trend of coercive field. Coercive field first increases from 78 to 210 Oe and then decreases to 174 Oe. The electrical transition temperature is found to be 158 K for 20nm particle. Oxygen deficiency in such system generally reduces Mn⁴⁺ to Mn³⁺ to keep the charge neutrality of the structure and hence it destroys the conduction path ways to mobile electrons, at least in long range, and thus insulating behavior becomes more prominent in the larger temperature range. The trend at lower temperature attribute to the coulomb blockade.