Impact of bicritical fluctuation on magnetocaloric phenomena in perovskite manganites

TL;DR

This study systematically explores how bicritical fluctuations influence the magnetocaloric effects in perovskite manganites, revealing that phase competition and fluctuations significantly shape the temperature and magnitude of entropy changes.

Contribution

It demonstrates the impact of bicritical fluctuations on magnetocaloric phenomena in manganites, highlighting the role of phase competition and chemical composition control.

Findings

Steeper drop in entropy change below T_C with reduced bandwidth.

Rectangular-shaped entropy change profile over a wide temperature range.

Model calculations show fluctuation effects are controllable via chemical composition.

Abstract

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.