Enhanced magnetocaloric effect in single crystalline Nd0.5 Sr0.5 Mn O3

The magnetocaloric effect in single crystalline Nd0.5 Sr0.5 Mn O3 (NSMO 0.5) is investigated by computing the field dependent entropy change (ΔS) and adiabatic temperature change (Δ Tad). At the charge ordering temperature (TCO), the value of Δ Smax is found to be much higher than Δ Smax reported in polycrystalline samples. This "giant" entropy change is attributed to interplay (stronger in single crystals) among spin, charge, lattice, and orbital degrees of freedom resulting in a field induced transition at TCO. In contrast, the change in entropy associated with Curie temperature (TC) is very low. The direct measurements of the field induced temperature change (ΔT) are in agreement with the computed value of ΔS. The presence of short-range correlations with charge/orbital order (COO) above and below TC may be responsible for the suppression of the negative MCE at TC. A critical exponent analysis of the paramagnetic (PM) to ferromagnetic (FM) transition using magnetization data yields mean-field-like values, which is likely to be operative in inhomogeneous systems such as NSMO 0.5 with correlated COO clusters larger than lattice parameter. © 2007 American Institute of Physics.