Spin dynamics, electrical and magnetic properties of (La0.5Pr0.5)0.7Pb0.3Mn1−xCuxO3 (x=0x=0, 0.02) perovskites

Magnetization, resistivity, and electron spin resonance (ESR) measurements were carried out to investigate spin dynamics, electrical and magnetic properties of (La0.5Pr0.5)0.7Pb0.3Mn1−xCuxO3 (x=0x=0, 0.02) perovskites. It was found that with Cu addition the Curie temperature decreased from 326 K for x=0 to 300 K for x=0.02x=0.02 composition. The x=0x=0 sample underwent a metallic–insulator transition at ∼130 K, whereas the x=0.02x=0.02 sample with higher resistivity exhibited an insulating behavior as a whole. It was furthermore found that asymmetrical ESR signals at low temperatures became Lorentzian at high temperatures above Tmin. The temperature dependence of the linewidth, ΔH(T)ΔH(T), at T>TminT>Tmin fits well to the one-phonon model, ΔH(T)=AT+BΔH(T)=AT+B. The activation energy Ea, determined from the ESR intensity with respect to temperature, are 0.16 and 0.14 eV for x=0x=0 and 0.02 compositions, respectively. In terms of our experimental results, it is reasonable to conclude that the Cu addition led to a suppression of the ferromagnetism and conductivity of the parent compound (x=0x=0).