Impact of bicritical fluctuation on magnetocaloric phenomena in perovskite manganites

Variation of magnetocaloric (MC) effects has been systematically investigated for colossal magnetoresistive (CMR) manganites R0.6Sr0.4MnO3 (R=La-Gd). As the one-electron bandwidth is reduced, the temperature profile of MC effect, i.e., field-induced entropy change, exhibits a steeper drop below the ferromagnetic transition temperature due to its first-order nature promoted by a competing charge-orbital ordering instability. For these small-bandwidth systems adjacent to the metal-insulator phase boundary, a rectangular-shaped profile for the entropy change emerges with an anomalously wide temperature range and a considerable magnitude. Model calculations have indicated that the fluctuation enhanced in the phase-competing region has a strong impact on such MC features, which can be extensively controlled by the chemical composition.