Magnetocaloric effect in LiLn6O5(BO3)3 (Ln = Gd, Tb, Dy, and Ho)

A series of lanthanide-rich oxyborates LiLn 6 O 5 (BO 3 ) 3 (LLnOB, Ln = Gd, Tb, Dy, and Ho) have been synthesized using high temperature solid state method. Their magnetic and magnetocaloric properties were investigated upon magnetic susceptibility ( χ ), magnetization ( M ), and isothermal magnetic entropy change ( −ΔS m ) measurements. The maximum  − ΔS m, max of LiGd 6 O 5 (BO 3 ) 3 is 44.7 J kg −1 K −1 at 4 K and Δμ 0 H  = 9 T, which is higher than the one of commercial Gd 3 Ga 5 O 12 (GGG, −ΔS m, max  = 41.8 J kg −1 K −1 at 2 K for Δμ 0 H  = 9 T). For LiHo 6 O 5 (BO 3 ) 3 , −ΔS m, max is 14.12 J kg −1  K −1 at 3 K and Δμ 0 H  = 2 T, which is also larger than that of Ho 3 Ga 5 O 12 (HoGG, − ΔS m, max  = 4.38 J kg −1 K −1 at 2 K for Δμ 0 H  = 2 T) and Dy 3 Ga 5 O 12 (DGG, − ΔS m, max  = 11.0 J kg −1 K −1 at 2 K for Δμ 0 H  = 2 T). These results indicate that LiGd 6 O 5 (BO 3 ) 3 and LiHo 6 O 5 (BO 3 ) 3 may be competitive candidates for applications as magnetic refrigerants. Moreover, thermal stability, infrared spectrum (IR), and ultraviolet–visible-near-infrared diffuse reflectance spectrum (UV–Vis-NIR) were carried out to characterize the title compounds.