Isothermal magnetic entropy behavior in Tb5Si3: Sign reversal and non-monotonic variation with temperature, and implications

TL;DR

This study investigates the magnetic entropy change in Tb5Si3, revealing sign reversal at the magnetic transition and linking positive magnetoresistance to magnetic fluctuations, supporting the concept of inverse metamagnetism.

Contribution

It uncovers the sign reversal and non-monotonic behavior of magnetic entropy in Tb5Si3, providing new insights into its magnetocaloric and magnetoresistive properties.

Findings

 Sign reversal of S at the magnetic transition temperature.

 High-field state shows higher entropy and positive S.

 Evidence supporting inverse metamagnetism in Tb5Si3.

Abstract

The magnetic entropy change (\DeltaS), a measure of the magnetocaloric effect, in Tb5Si3, a compound exhibiting unusual positive magnetoresistance following a magnetic-field-induced transition below magnetic transition temperature (~ 69 K), has been investigated. We found that \DeltaS is negative in the paramagnetic state. At the magnetic transition temperature, \DeltaS shows sign reversal from negative (in the paramagnetic state) to positive value in the magnetically ordered state. The high-field state which is interestingly the high resistive state is found to be associated with higher entropy i.e. large positive \DeltaS, behaving like a paramagnet. On the basis of this observation, we conclude that the magnetic field induces magnetic fluctuations in the system resulting in positive magnetoresistance, thereby rendering support to the idea of 'inverse metamagnetism' in this compound. In addition, we note that Arrott plots present an interesting scenario.