Thermo-magnetic characterization of phase transitions in a Ni-Mn-In metamagnetic shape memory alloy

Abstract

The partially overlapped ferroelastic/martensitic and para-ferromagnetic phase transitions of a Ni${}_{50.53}$Mn$33.65$In${}_{15.82}$ metamagnetic shape memory alloy have been studied from calorimetric, magnetic and acoustic emission measurement. We have taken advantage of the existence of thermal hysteresis of the first order ferroelastic/martensitic phase transition ($\sim 2.5$K) to discriminate the latent heat contribution $\Delta$Ht = 7.21(15) kJ/kg and the specific heat contribution $\Delta$Hc = 216(1) J/kg to the total excess enthalpy of the phase transition. The specific heat was found to follow a step-like behavior at this phase transition. The intermittent dynamics of the ferroelastic/martensitic transition has been characterized as a series of avalanches detected both from acoustic emission and calorimetric measurements. The energy distribution of these avalanche events was found to follow a power law with a characteristic energy exponent $\epsilon \sim 2$ which is in agreement with the expected value for a system undergoing a symmetry change from cubic to monoclinic. Finally, the critical behavior of the para-ferromagnetic austenite phase transition that takes place at $\sim 311$K has been studied from the behavior of the specific heat. A critical exponent $\alpha \sim 0.09$ has been obtained, which has been shown to be in agreement with previous values reported for Ni-Mn-Ga alloys but different from the critical divergence reported for pure Ni.

18 pages, 11 figures

References in corpus (1)

• Calorimetric and magnetic study for Ni${}_{50}$Mn${}_{36}$In${}_{14}$ and relative cooling power in paramagnetic inverse magnetocaloric systems

Cited by in corpus (2)

• Ultraslow calorimetric studies of the martensitic transformation of NiFeGa alloys: detection and analysis of avalanche phenomena
• In situ coherent X-ray scattering reveals polycrystalline structure and discrete annealing events in strongly-coupled nanocrystal superlattices