The structural, magnetic and magnetocaloric properties of Ba doped La manganites

The structural, magnetic and magnetocaloric properties of barium doped lanthanum manganites La1-xBaxMnO3 with x = 0.1, 0.2 and 0.3 compositions were investigated. The X-ray powder diffraction results show that all samples crystallize in the rhombohedral R-3c space group. The substitution of La3+ by the larger Ba+2 ions induces an increase of the unit cell volume when the doping level increases from 10% to 20%. On the contrary a further increase of Ba doping at 30% causes a decrease in the volume of unit cell. All samples exhibit a ferromagnetic to paramagnetic transition. Transition temperature increases from 181 K to 319 K with increasing doping level. Above transition temperature the paramagnetic behavior of the samples is well described by the Curie - Weiss law. Arrott-Belov plots show that all samples follow the behavior expected for a conventional second order transition. The magnetic entropy change and relative cooling power have been determined. vertical stroke ΔSmaxM vertical stroke observed in the vicinity of transition temperature increases monotonically from 1.51 Jkg-1K-1 for x = 0.1 to 2.61 Jkg-1K-1 for x = 0.3 for a field change of 2 T. The observed temperature dependence of ΔSM is explained reasonably well by the Landau theory of second order phase transition. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)