Enhanced Cryogenic Magnetocaloric Effect from 4f‐3d Exchange Interaction in B‐Site Ordered Gd2CuTiO6 Double Perovskite Oxide

Abstract Magnetic refrigeration based on the principle of the magnetocaloric effect (MCE) in magnetic solids has been considered as a prospective cooling technology. Exploring suitable magnetocaloric materials (MCMs) is a vital prerequisite for practical applications. Herein, an excellent cryogenic MCM—the B ‐site‐ordered Gd 2 CuTiO 6 double perovskite (DP) oxide—which exhibits the largest MCE among known Gd‐based DP oxides, is identified. Such enhanced cryogenic MCE in the Gd 2 CuTiO 6 DP oxide likely stems from the exchange interaction effect between Gd‐4 f and Cu‐3 d magnetic sublattices. Under a magnetic field change of 0–7 T, the maximum magnetic entropy change (−Δ S T max ) of the Gd 2 CuTiO 6 DP oxide reaches 51.4 J kg −1 K −1 (378.2 mJ cm −3 K −1 ), which is much larger than that of the commercialized magnetic refrigerant Gd 3 Ga 5 O 12 , which is 38.3 J kg −1 K −1 (271.2 mJ cm −3 K −1 ), and it is also superior to most of the recently reported benchmarked cryogenic MCMs, indicating the possibility for practical applications. This work also provides a productive route for future cryogenic MCM design by harnessing 4 f– 3 d exchange interactions.