The persistence of the magnetocaloric effect in (La1-xAx)0.67Ba0.33Mn1.05O3-δ

Polycrystalline samples of (La(1-x)A(x))(0.67)Ba0.33Mn1.05O3-delta, with A being a mixture of lanthanides containing 66% La, 22% Nd, 8% Pr, and 4% Ce, were prepared by the glycine-nitrate method, with target compositions of x=0, 0.33, 0.67, and 1. The effect of the mixture of lanthanides on the Curie temperature, T-C, and the magnetocaloric properties was investigated. The prepared samples are single phase, with space group R (3) over barc. The lattice parameters and average A-site ionic radius, r(A) decrease linearly with x while the size disorder, as characterized by the variance, sigma(2), increases from 0.014 to 0.017 with x. As x is increased, the increase in sigma(2) drives a linear decrease in TC. The magnetic entropy change, Delta S-M, for a field change of 1 T is obtained by magnetization measurements, giving a maximum value of 1.7 J/kg K, and a relative cooling power of 43 J/kg, independent of x. These results suggest that replacing lanthanum with a mixture of lanthanides is a realistic way to tune the working temperature of magnetocaloric manganites while maintaining a constant magnetocaloric effect. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490222]