Unconventional metamagnetic phase transition in R2In (R=Nd, Pr) with lambda-like specific heat and nonhysteresis

Abstract The phase transition of Nd2In and Pr2In has been studied and found to be between the first-order and second-order nature. Hardly any hysteresis nor obvious cell volume changes are presented. Concurrently the field-triggered metamagnetism is demonstrated with lambda-like peak on specific heat curve. For the field change of 7 T, giant magnetic entropy changes of 13.2 J kg−1 K−1 and 19.5 J kg−1 K−1 and adiabatic temperature changes of 6.5 K and 7.4 K have been achieved in Nd2In and Pr2In alloys respectively, which is partially contributed by strong magnetoelastic coupling represented by high saturation magnetostriction of ∼450 ppm. Such unique feature is proposed to be originated from the delocalized 5d electrons, as evidenced by the negative magnetoresistance caused by the phase transition.