We examine the character of the itinerant magnetic transition of DyCo2 by different calorimetric methods, thereby separating the heat capacity and latent heat contributions to the entropy-allowing direct comparison to other itinerant electron metamagnetic systems. The heat capacity exhibits a large lambda-like peak at the ferrimagnetic ordering phase transition, a signature that is remarkably similar to La(Fe,Si)(13), where it is attributed to giant spin fluctuations. Using calorimetric measurements, we also determine the point at which the phase transition ceases to be first order: the critical magnetic field, mu H-0(crit) = 0.4 +/- 0.1 T and temperature T-crit = 138.5 +/- 0.5 K, and we compare these values to those obtained from analysis of magnetization by application of the Shimizu inequality for itinerant electron metamagnetism. Good agreement is found between these independent measurements, thus establishing the phase diagram and critical point with some confidence. In addition, we find that the often-used Banerjee criterion may not be suitable for determination of first order behavior in itinerant magnet systems. DOI: 10.1103/PhysRevB.87.134421

We have performed scanning Hall probe imaging experiments to study the martensite to austenite phase transition in the Ni50(Mn, 1%Fe)34In16 alloy as a function of temperature and magnetic field. We observe that the martensite and austenite phase regions are separated by a distinct interface. The relative growth of phase across the phase transition is associated with the movement of this interface. The movement of the interface becomes arrested at low temperature, which leads to the formation of a “magnetic glass” state in the alloy. The dynamics of the martensite to austenite phase transition in the Ni50(Mn, 1%Fe)34In16 alloy is found to be qualitatively different when the transition is field induced than what it is when the same transition is induced by temperature. While both nucleation and growth of the martensite phase is observed during the austenite to martensite phase transition in the alloy during cooling down, the martensite to austenite phase transition during warming up appears to be growth oriented. In contrast, both nucleation and growth of the product phases are observed during the field induced martensite to austenite phase transition both during increasing and decreasing field experiments. The physical reasons behind these different observations are explored.