Effect of Mn-Site for Al Substitution on Structural, Electrical and Magnetic Properties inLa0.67Sr0.33Mn1-xAlxO3Thin Films by Sol-Gel Method

Abstract

NanocrystallineLa0.67Sr0.33Mn1-xAlxO3(x=0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) thin films have been prepared on quartz substrates by sol-gel method. The structural and morphology studies were investigated via X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). XRD graph patterns show rhombohedral distorted perovskite structures. FESEM images show that the average grain size decreased as the concentration ofxincreased. Electrical property was investigated using four-point probe technique. Resistivity results show that metal-insulator transition (MIT) temperatures (Tp) decreased when the concentration ofxincreased.Tpshifted to lower temperature when the concentration ofxincreased. The data was analyzed based on theoretical models, where the ferromagnetic resistivity is followed with the equationρ=ρo+ρ2T2, whereρois due to the significance of grain boundary effects and a second-term ~ρ2T2appears that might be applied to the electrons scattering. In the high temperature regime(T>Tp), the resistivity data can be well described by small polaron hopping (SPH) and variable range hopping (VRH) mechanisms. Magnetic property was investigated using a vibration sample magnetometer. All samples that were obtained showed hysteresis curve with the highest value of magnetization for samplex=0.10.