Magnetic influence on the martensitic transformation entropy in Ni-Mn-In metamagnetic alloy

Abstract

We study the martensitic transformation (MT) of metamagnetic shape memory alloy Ni50Mn34.5In15.5 in the magnetic fields up to 12 T. The observed dependence of the MT temperature, Tm, on the field is highly nonlinear. As far as magnetization change, ΔM, remains field-independent, a depart from linearity of Tm(H) function is attributed to a decrease of the transformation entropy, ΔS. This decrease correlates with the parameter (TC-Tm), controlled by magnetic field, where TC is the Curie temperature of austenite, and with the dependence of ΔS on the width of the MT temperature interval deduced from a ferroelastic model of MT.

An interpretation of the kinetics of martensitic transformation in a Ni45Co5Mn36.5In13.5 alloy

“…9, we know that the entropy change Ds at M s decreases as M s decreases. Therefore, Ds at M s comes to decrease with increasing magnetic field, as reported by Barandiaran et al [23] for a Ni 50 Mn 34.5 In 15.5 alloy. Concerning the dependence of Ds on the temperature, Umetsu et al [24] reported that the sign of Ds changes at $80 K for a Ni 50 Mn 34 In 16 alloy, and they interpreted that such an anomalous behavior in Ds is responsible for the kinetic arrest of MT in that system.…”

Transformation Volume Effects on Shape Memory Alloys

“…T T − to S Δ was verified very recently in the experiments with Ni-Mn-In alloys (see Figure 15) [96]. Figure 15.…”

“…Figure 15. The experimental verification of the inverse proportionality of two-phase temperature interval to entropy change [96]. The dashed line presents a linear fit to the experimental points.…”

Thermodynamics and Kinetics of Martensitic Transformation in Ni-Mn-based Magnetic Shape Memory Alloys

“…However, due to the large magnetic anisotropy in Ni-Mn-Ga alloys [2,91], a low magnetic field results in a small decrease of T M s [88,89]. Nevertheless, for Ni-Mn-In alloys, the magnetization of the parent phase is much greater than that of martensite phase, and thus magnetic fields will effectively decrease the T M s [23,[92][93][94][95][96], as is schematically shown in Fig. 2.3(c).…”