A-site-disorder-dependent magnetocaloric properties in the mono-valent-metal doped La sub(0.7Ca) sub(0).3MnO sub(3 manganites)

The influence of mono-valence-metal (Li, Na, and K) doping effect on the structural, resistivity, magnetic and magnetocaloric properties of La sub(0.7Ca) sub(0).3MnO sub(3 polycrystalline samples is studied for a fixed (5% at Ca site) dopant concentration. All the samples crystallize in orthorhombic structure and the lattice parameters increase continuously as the dopant atoms changes from Li to Na and then K. Paramagnetic-ferromagnetic phase transition at T) sub(C) and insulator-metal phase transition at T sub(p are observed for all studied samples. The transition temperature decreases as Ca atoms is replaced by Li, while the transition temperature shifts to higher values as Ca is substituted by Na or K. In addition, the maximum magnetic entropy change of the K-doped sample is much smaller than that of the free- and Na-doped samples. The results are discussed according to the change of A-site-disorder effect caused by the systematic variations of A-site average ionic radius [inline image]r) sub(A)[inline image] and A-site-cation mismatch [sigma][super]2.