Enhanced Cryogenic Magnetocaloric Effect from 4 f ‐3 d Exchange Interaction in B ‐Site Ordered Gd 2 CuTiO 6 Double Perovskite Oxide

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.