Growth and magnetocaloric effect of Na2Gd2(BO3)2O crystal

High-quality Na 2 Gd 2 (BO 3 ) 2 O crystals have been successfully grown using the top-seeded solution growth method (TSSG), employing a Na 2 O - NaF - B 2 O 3 flux system with optimal molar ratios of Na 2 Gd 2 (BO 3 ) 2 O : Na 2 CO 3 : NaF : H 3 BO 3  = 1:2:6:4. The magnetic and magnetocaloric properties were investigated including magnetic susceptibility ( χ ), magnetization ( M ), and isothermal magnetic entropy change ( −ΔS m ) measurements. Na 2 Gd 2 (BO 3 ) 2 O exhibits a large magnetocaloric effect with a maximum  − ΔS m of 41.6 J·kg −1 ·K −1 at 2 K and 7 T, which is higher than that of commercial Gd 3 Ga 5 O 12 (GGG, −ΔS m = 38.4 J·kg −1 ·K −1 at 2 K and 7 T) and most other Gd 3+ -based borates, showing the potential application in the field of magnetic refrigeration.