Effect of Cr doping on the structural magnetic and transport properties of perovskite-like manganites

Abstract

Structural, magnetic and transport measurements were performed on La0·7Sr0·3Mn1-xCrxO3 (0≤x ≤ 0.15) perovskite-like manganites in order to study the effect of the substitution on the Mn-site on the magnetotransport properties. All samples are found to be of single phase. The structural parameters obtained by using Rietveld refinement of X-ray diffraction data show that all samples crystallize with rhombohedral perovskite-type symmetry with R3‾c space group. The concentration dependence of the unit cell parameters indicates that chromium (or most of the chromium) has a trivalent state. The magnetization and electric measurements reveal that all the samples demonstrate a ferromagnetic to paramagnetic transition and a metallic to semiconductor one with increasing temperature. The Curie temperature TC and the resistivity transition temperature Tms shift to lower values with increasing Cr content. The correct expression for bandwidth W ~ TC is given. The temperature dependence of electrical resistivity supports the small polaron hopping model and variable range hopping conduction model above the metal–semiconductor transition temperature (Tms). The calculated hopping distance and hopping energy increased as rate of Cr content increased whereas density of states at Fermi level decreased.