Evidence of large magnetic cooling power and double glass transition in Tb5Pd2

We report a detailed dc magnetization, ac susceptibility and magnetocaloric properties of a binary intermetallic compound Tb5Pd2. Our dc magnetization and heat capacity results reveal absence of long range ordering in this compound. Two distinct frequency dependent peaks (Tf1~60 K and Tf2~21 K) had been observed in the ac-susceptibility. Analysis of these frequency dependent peaks by Mydosh parameter, power and Vogel-Fulcher law reveals that around Tf1 the compound is at the boundary of spin glass (SG) like-cluster glass (CG) like state and it undergoes a cluster glass-like freezing below Tf2. Zero field cooled memory effect and non-linear dc susceptibility also confirmed the presence of two glassy transitions in this compound. The transformation from SG/CG boundary to CG phase was also confirmed by the magnetic relaxation measurement and Arrott plots study. Remarkably, a significant magnetic entropy change was also observed in the temperature range of 60-120 K. Additionally a large relative cooling power also observed in this compound. The observed value is comparable to those of promising refrigerant material in this temperature range and is quite notable as in this compound magnetic hysteresis was absent in this temperature range. It was noted that in this compound short-range interactions persist up to a higher temperature above Tf1 and this is responsible for the observation of significant MCE over a wide temperature range. Our studies suggest that this compound is an example of a glassy magnetic compound which shows large magnetocaloric effect.

Mohit K. Sharma, K. Mukherjee · 2018