Entropy change and kinetic effects at the magnetostructural phase transition of MnBi

In this paper we investigate the entropy change and the kinetics at the magneto-structural transition (at 628 K) of polycrystalline MnBi. Samples were prepared by rapid quenching and annealing and exhibit 86 wt% of the hexagonal MnBi phase. The entropy change at the transition is found to be Delta s = 17.6 J kg(-1) K-1 and the magnetic field shifts the transition temperature at a rate of 2.6 K T-1. The temperature hysteresis, of 19 K, is quite large for magneto-thermal application. The transition shows kinetics effects upon cooling in which the transition temperature is found to depend approximately to the logarithm of the temperature rate with coefficient -3.8 K. (C) 2013 Elsevier Ltd and IIR. All rights reserved