Magnetocaloric Effect and Critical Behavior of La _0.67 Ca _0.33 MnO ₃ @ZIF-67 Composites

The development of near-room-temperature magnetic refrigeration relies on magnetic materials with large entropy changes and broad operating ranges. Here, we report an interface functionalization strategy to construct La 0.67 Ca 0.33 MnO 3 @ZIF-67 composites via in-situ growth method. The introduction of ZIF-67 increased the specific surface area and created abundant mesopores. The composite with low ZIF-67 content (La 0.67 Ca 0.33 MnO 3 @ZIF-67-1) showed an enhanced maximum magnetic entropy change (3.66 J·kg -1 ·K -1 ) and relative cooling power (251.8 J·kg -1 ) under 5 T compared to the pure La 0.67 Ca 0.33 MnO 3 . However, higher ZIF-67 loading degraded magnetocaloric performance due to the dilution effect of the non-magnetic phase. Notably, critical behavior analysis revealed a shift from the Ising model in pure La 0.67 Ca 0.33 MnO 3 , indicative of short-range interactions, to the mean-field model in composites, dominated by long-range interactions. This indicated that ZIF-67 suppressed critical magnetic fluctuations through interfacial coupling and physical isolation. This study confirmed that interfacial regulation using non-magnetic porous metal-organic frameworks (MOFs) is an effective approach for optimizing the magnetocaloric properties of perovskite manganites and modulating their phase transition behaviors.