Effect of Nd-substitution on the structural, magnetic and magnetocaloric properties of La0.67-xNdxCa0.13Ba0.2MnO3 manganites

摘要

The effects of the substitution of La3+ by smaller rare-earth ion Nd3+ on the structural, magnetic and magnetocaloric properties of La0.67-xNdxCa0.13Ba0.2MnO3 (x = 0.02, 0.06, 0.1) manganites prepared by solid state sintering technology have been investigated. X-ray diffraction analysis shows that the x = 0.02 sample crystallizes in the rhombohedral structure with R (3) over barc space group symmetry and the x = 0.06, 0.1 samples belong to the orthorhombic structure with Ibmm space group. The Rietveld refinements for all samples were carried out to investigate on the crystal structures of the samples. Thermomagnetic measurements indicate that all the samples exhibit a magnetic transition from ferromagnetic to paramagnetic phase with increasing temperature. The Curie temperature T-C systematically decreases from 308 K to 280 K with the accumulation of Nd concentration. Critical analysis demonstrates that the estimated critical exponents beta, gamma and delta are between the theoretically predicted values for 3D-Ising and mean-field theory models for all samples. The magnetic entropy change has been calculated from the isothermal magnetization measurements as a function of the applied magnetic field at various temperatures near T-C . The maximum magnetic entropy change -Delta S-max under an applied magnetic field of 1.6T was found to be 3.06, 2.92 and 2.48 J kg(-1 )K(-1) respectively for x = 0.02, 0.06 and 0.1 samples. This indicates that these manganites are remarkably potential functional materials working as magnetic refrigerants near room temperature.