Rare earth effect on structural, magnetic and magnetocaloric properties of La0.75Ln0.05Sr0.2MnO3 manganites

In this work, we have investigated the rare earth substitution effect on structural, magnetic and magnetocaloric properties of La(0.75)Ln(0.05)Sr(0.2)MnO(3) polycrystalline manganites (Ln(=)La, Sm, Eu, Gd, Dy and Ho), synthesized using the sol-gel technique. Replacing La with other rare earth elements induces an enhancement of cationic mismatch inducing a structural transition from rhombohedral to orthorhombic symmetry for highly disordered samples. Temperature dependence of magnetization indicates that our samples undergo a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature values decrease with the mismatch increase, but Ho based sample shows a different behavior. The magnetic entropy change curves -Delta S(T) show a large magnetocaloric effect near room temperature. We have also improved the magnetocaloric effect by using theoretical calculation to get theoretical composites.