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

The magnetic entropy change ( Δ S ), a measure of the magnetocaloric effect, in Tb5Si3, a compound exhibiting unusual positive magnetoresistance following a magnetic-field-induced transition below the magnetic transition temperature (∼69 K), has been investigated. We found that Δ S is negative in the paramagnetic state. At the magnetic transition temperature, Δ S shows a sign reversal from a negative value (in the paramagnetic state) to a 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 Δ S , 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 the Arrott plots present an interesting scenario.