Spin Fluctuation Effect on Electrical Resistivity of La0.8Ca0.2MnO3 Manganite Nanoparticles

The electrical resistivity rho(T) of La0.8Ca0.2MnO3 manganite nanoparticles (particle size 18 nm and 70 nm) significantly depends on temperature and size of nanoparticles. rho(T) of 70 nm La0.8Ca0.2MnO3 manganite exhibits metallic phase in low temperature regime (T < 250 K), develops a maxima near 250K and decrease with T at high temperatures (250K < T < 300 K). However, the rho(T) of 18 nm La0.8Ca0.2MnO3 manganite shows insulating phase in overall temperature regime, where resistivity decrease with temperature. The resistivity in metallic phase is theoretically analyzed by considering the strong spin fluctuations effect which is modelled using Drude-Lorentz type function. In addition to the spin fluctuation-induced contribution the electron-phonon and electron-electron rho(e-e)(T) - BT2 contributions are also incorporated for complete understanding of experimental data. The contributions to the resistivity by inherent acoustic phonons (rho(ac)) as well as high frequency optical phonons (rho(op)) were estimated using Bloch-Gruneisen [BG] model of resistivity. It is observed that the resistivity contribution due to electron-electron interaction shows typical quadratic temperature dependence. Resistivity in Semiconducting/insulating phase is discussed with small polaron conduction (SPC) model. Finally the theoretically calculated resistivity compared with experimental data which found consistent in wide range of temperature.