Structure, magnetic properties and magnetocaloric effect of gadolinium-titanium-based B-site low, medium and high-entropy double perovskite oxides

The heavy rare earth-based quaternary double perovskite Gd 2 B TiO 6 is expected to become one of the candidate materials for magnetic refrigeration due to its high chemical stability, low magnetic ordering temperature, and giant magnetocaloric effect. This work conducted experimental investigation on the structure, magnetic behavior, and magnetocaloric property of B -site low, medium and high-entropy Gd 2 B TiO 6 structural oxides. The structural analyses indicate that the prepared samples belong to a monoclinic double perovskite structure with uniform composition. The magnetic measurement results indicate that these samples exhibit a reversible magnetization process. Remarkable magnetocaloric effect is observed at the lowest measured temperature despite a lack of magnetic order. Large paramagnetic moment of Gd 3+ could play an important role. The values of magnetic entropy change -∆ S M ( T ) ( T = 4   K, Δ H = 6   T) are 27.2, 30.3, 28.7, 32.1, and 25.1   J·kg -1 ·K -1 for Gd 2 ( B )TiO 6 , Gd 2 (2 B 1/2 )TiO 6 , Gd 2 (3 B 1/3 )TiO 6 , Gd 2 (4 B 1/4 )TiO 6 , and Gd 2 (5 B 1/5 )TiO 6 , respectively. This work may provide some inspiration for the design and development of low-temperature magnetic refrigeration materials.