Structure, magnetic and electrical properties of La0.6Sr0.4−xKxMnO3 perovskites

The effect of the monovalent chemical substitution of K+ into Sr2+ sites on the structural, magnetic and electrical properties of La0.6Sr0.4−xKxMnO3 (0 ≤ x ≤ 0.15) has been investigated. The rhombohedral distorted perovskite structure with space group R3¯c is observed in this series of materials while the average size 〈rA〉 and Mn3+/Mn4+ ratios are varied simultaneously. The Rietveld refinement of the structure shows that the substitution of Sr by K in the La site changes the structure parameters such as the MnO bond length and MnOMn angles. An increase in the MnO bond length with increasing K content leads to a decrease in the paramagnetic-ferromagnetic transition temperature TC and the metal-semiconductor transition temperature Tp. A magnetoresistance ratio of about 38% at 300 K and in an applied field of 8 T has been observed in the bulk ceramic La0.6Sr0.25K0.15MnO3.