Large Magnetocaloric Effect in Gd2Si2O7 and Plateau-Like Magnetic Entropy Change in Dy2Si2O7

We report the magnetic properties and magnetocaloric effects (MCE) of R2Si2O7 (R = Gd, Dy) with different crystal structures. For the orthorhombic Gd2Si2O7 (Type E), no signature of long-range magnetic ordering is observed down to 2 K. What is very impressive is the maximum magnetic entropy change ( -dSmax M ) of 58.81 J kg-1 K-1 at 3 K, which is 82.1 % of the theoretical value 2Rln8 (71.637 J kg-1 K-1), for a field change of Delta B = 0 -7 T. For the triclinic Dy2Si2O7 (Type B), it is long-range antiferromagnetically ordered at TN = 1.92 K. Importantly, the -dSMpresents a plateau-like behavior within 6-12 K with three local maxima. The value of -dSmax M is about 20.33 J kg-1 K-1 for 0 -7 T at 12 K (much higher than TN). Thus, the large MCE in Gd2Si2O7 and the plateau-like magnetic entropy change in Dy2Si2O7 make them potential candidates for magnetic refrigeration in the low temperature range.