Improved crystallographic compatibility and magnetocaloric reversibility in Pt substituted Ni2Mn1.4In0.6 magnetic shape memory Heusler alloy

Abstract

We present here the improved crystallographic/geometric compatibility and magnetocaloric reversibility by measurement of magnetic entropy change using different protocols in 10% Pt substituted Ni2Mn1.4In0.6 magnetic shape memory alloy. The substitution of Pt reduces the thermal hysteresis about 50% to the Ni2Mn1.4In0.6. The origin of the reduced thermal hysteresis is investigated by the crystallographic compatibility of the austenite and martensite phases. The calculated middle eigenvalue of the transformation matrix turned out to be 0.9982, which is very close to 1 (deviation is only 0.18%) suggests for the crystallographic compatibility between the austenite and martensite phases in Ni1.9Pt0.1Mn1.4In0.6. A very small thermal hysteresis and crystallographic compatibility between two phases in this alloy system indicate a stress-free transition layer (i.e. perfect habit plane) between the austenite and martensite phase, which is expected to give reversible martensite phase transition and therefore reversible magnetocaloric effect (MCE) as well. The calculated value of the isothermal entropy change (ΔSiso) using the magnetization curve under three different measurement protocols (i.e. isothermal, loop, and isofield measurement protocol) is found to be nearly same indicating a reversible MCE in the present alloy system. Our work provides a path to design new magnetic shape memory Heusler

Large magnetocaloric effect in rapidly quenched Mn50− x Co x Ni40In10 nanomaterials

“…Furthermore, there is a substantial decrease in the thermal hysteresis of M(T) curve (∆T) at phase transition, where ∆T decreases from 48 K for Mn 50 Ni 40 In 10 to 33 K for Mn 47 Co 3 Ni 40 In 10 . Possible reasons for this decrease in thermal hysteresis are better crystallographic compatibility between martensite and austenite phases or the decrease in the latent heat of transformation due to Co doping [20,36]. Although there is significant decrease in ∆T due to Co doping, the thermal hysteresis still remains a limiting factor for the practical applicability of these materials.…”

Microstructural characterization and functional performance of Ni54Mn25Ga21-xDyx high-temperature shape memory alloys

“…However, a complicated and abnormal dependence of on the middle eigenvalue was observed as the investigated alloys still showed extremely low thermal hysteresis though λ 2 was far from unity. For an in-depth understanding of the discrepancy, a systematic comparison was conducted among documented results for other SMAs undergoing different lattice transitions as shown in Figure 10 [21,23,25,35-47]. In general, there mainly exist three transitions including cubic to orthorhombic, cubic to monoclinic and cubic to tetragonal transitions, denoted as COT, CMT and CTT, respectively.…”

Prediction of Magnetocaloric Effect Induced by Continuous Modulation of Exchange Interaction: A Monte Carlo Study

“…The relationship between MCE and phase transitions implies the anisotropy and exchange energies responsible for the large MCE besides the external magnetic field, and from the energy-saving point of view, the rotary MCE based on the anisotropy contributing to ∆ S M has been developed and studied for the aim of reducing the cost of external magnetic field energy [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. On the other hand, effective methods to control the magnetocaloric properties and their working temperatures (probably around the magnetic phase transition temperature) such as partial substitution [ 22 , 23 ], application of hydrostatic pressure [ 24 ], and hydrogenation [ 25 ] have been proposed. Theoretically, Buchelnikov et al [ 26 ] and Sokolovskiy et al [ 27 ], using Monte Carlo simulations combined with ab initio calculations, studied the micromagnetism and magnetocaloric effect in Co-doped off-stoichiometric Ni-Mn-Ga and Ni-Mn-In Heusler alloys, and the numerical results of magnetic and magnetostructural transitions under a magnetic field agreed fairly well with available experimental data.…”