Implicit measurement of the latent heat in a magnetocaloric NiMnIn Heusler alloy

Abstract

The latent heat linked with the first-order transformation of a NiMnIn Heusler alloy has been studied through direct measurements of the adiabatic temperature change, ΔTad, during magnetization process. The experimental procedure used guarantees independent data points and negates any contribution of hysteretic losses to the magnetocaloric effect. Thus, the differences between the magnitudes of ΔTad measurements during the magnetization with the initial temperature change directions from low-to-high and high-to-low are solely attributed to the latent heat exchange, which accompanies the irreversible structural first-order transformation. An estimate of the latent heat inducing such differences is about 0.292 J/g.

Novel Achievements in the Research Field of Multifunctional Shape Memory Ni-Mn-In and Ni-Mn-In-Z Heusler Alloys

“…In a closely related compound Ni 50 Mn 34.8 In 14.2 B, direct measurements of the magnetization and the differential scanning calorimetry have shown that Ni 50 Mn 34.8 In 14.2 B exhibits a magnetostructural first-order phase transition from a ferromagnetic martensitic phase to a paramagnetic austenitic phase [68]. In another example, measurements of the adiabatic temperature change and the latent heat in Ni 2 MnIn alloy revealed a transition from a FM to a FRM state that is also of the first-order [82]. The phenomenological Ginzburg-Landau theory for the description of the experimentally observed sequences of phase transitions in Ni 50 Mn 35 In 15 Heusler alloy is proposed by Zagrebin et al [83].…”

Distribution of Transition Temperatures in Magnetic Transformations: Sources, Effects and Procedures to Extract Information from Experimental Data

“…Magnetostructural transitions, such as those occurring in magnetic Heusler alloys [4], imply the reversible (although generally hysteretic) structural change from a low entropy, low symmetry, and low temperature phase (i.e., martensite) to a high entropy, high symmetry, and high temperature phase (i.e., austenite). Unlike the former described transitions, magnetostructural ones present a latent heat of the transformation and can be thermally activated (i.e., the transition temperature can be shifted with the heating or cooling rate) [5]. The magnetic nature of the austenite and martensite phases is diverse.…”