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

A series of lanthanide-rich oxyborates LiLn(6)O(5)(BO3)(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 (chi), magnetization (M), and isothermal magnetic entropy change (-Delta S-m) measurements. The maximum -Delta S-m, max of LiGd6O5(BO3)(3) is 44.7 J kg(-1) K-1 at 4 K and Delta mu H-0 = 9 T, which is higher than the one of commercial Gd3Ga5O12 (GGG, -Delta S-m, (max) = 41.8 J kg(-1) K-1 at 2 K for Delta mu H-0 = 9 T). For LiHo6O5(BO3)(3), -Delta S-m, (max) is 14.12 J kg(-1) K-1 at 3 K and Delta mu H-0 = 2 T, which is also larger than that of Ho3Ga5O12 (HoGG, -Delta S-m, max = 4.38 J kg(-1) K-1 at 2 K for Delta mu H-0 = 2 T) and Dy3Ga5O12 (DGG, Delta S-m, max = 11.0 J kg(-1) K-1 at 2 K for Delta mu H-0 = 2 T). These results indicate that LiGd6O5(BO3)(3) and LiHo6O5(BO3)(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.