Magnetocaloric effect and refrigerant capacity in charge-ordered manganites

The influence of first- and second-order magnetic phase transitions on the magnetocaloric effect (MCE) and refrigerant capacity (RC) of charge-ordered Pr 0.5 Sr 0.5 MnO 3 has been investigated. The system undergoes a paramagnetic to ferromagnetic transition at T C ∼ 255 K followed by a ferromagnetic charge-disordered to antiferromagnetic charge-ordered transition at T CO ∼ 165 K . While the first-order magnetic transition (FOMT) at T CO induces a larger MCE ( 6.8 J / kg K ) limited to a narrower temperature range resulting in a smaller RC (168 J/kg), the second-order magnetic transition at T C induces a smaller MCE ( 3.2 J / kg K ) but spreads over a broader temperature range resulting in a larger RC (215 J/kg). In addition, large magnetic and thermal hysteretic losses associated with the FOMT below T CO are detrimental to an efficient magnetic RC, whereas these effects are negligible below T C because of the second-order nature of this transition. These results are of practical importance in assessing the usefulness of charge-ordered manganite materials for active magnetic refrigeration, and Pr 0.5 Sr 0.5 MnO 3 provides an interesting case study in which the influence of first- and second-order transitions on MCE could be compared in the same system in a single experiment.