Low-temperature heat-capacity studies of R2Ni3Si5 (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho)

Abstract

We report here our low temperature (2-30 K) hear capacity, C-p measurements of R2N3Si5 (R = Pr, Nd, Sm, Gd-Ho). Large peaks in heat capacity data at magnetic transition temperatures (T-N) confirm the bulk nature of magnetic order in these compounds. In Nd2Ni3Si5, Gd2Ni3Si5, and Dy2Ni3Si5, magnetization studies indicated only one magnetic transition, whereas, hear-capacity data show two transitions. T-N of the heavier rare-earth member, Tb2Ni3Si5, showing significant deviation from de Gennes scaling is notable. Magnetic entropy, Delta S, estimated from heat-capacity data suggest that the magnetic ground state is a doublet in R2Ni3Si5 (R = Pr, Nd, Sm, Dy, Ho) and a quartet in Tb2Ni3Si5. In all the cases, Delta S, at T-N is slightly less than that expected due to the suggested states, which we attribute to the occurrence of precursor effects of magnetic order above T-N. Except for Gd2Ni3Si5,, Delta S of the compounds does not reach the saturation limit of R ln(2J+1) even at 30 K, indicating the presence of crystalline electric field (CEF) effects. A hump in C-p is observed below T-N in Gd2Ni3Si5 which is interpreted in terms of a possible amplitude-modulated magnetic spin structure. [S0163-1829(99)12605-5].