K 3 Li 3 Gd 7 (BO 3 ) 9 : A New Gadolinium‐Rich Orthoborate for Cryogenic Magnetic Cooling

Abstract Magnetic cooling technology based on magnetocaloric effect (MCE) has attracted great interest in obtaining extremely low temperatures, for example, for space exploration. Here, we grew a new gadolinium‐rich orthoborate K 3 Li 3 Gd 7 (BO 3 ) 9 ( 1 ) as a promising cryogenic magnetic coolant. It exhibits a complicated three dimensional framework constructed from BO 3 groups and gadolinium‐oxygen chains. The Gd−O chain consists of two types of clusters of Gd 3 O 20 and Gd 3 O 19 interconnection by Gd(4)O 8 polyhydron. Due to its high gadolinium concentration, a large −Δ S m of 56.6 J kg −1  K −1 for 1 was obtained at 2 K and Δ H =7 T, much larger than that of the commercial benchmark Gd 3 Ga 5 O 12 (GGG) crystal (38.4 J kg −1  K −1 ), suggesting it to be an excellent MCE material.