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

• Published in: Journal of magnetism and magnetic materials 2020-08, Vol.507, p.166818, Article 166818
• Main Authors: Dubey, K.K., Devi, P., Singh, Anupam K., Singh, Sanjay
• Format: Article
• Language: English
• Subjects: Alloy systems; Alloys; Austenite; Compatibility; Crystallography; Eigenvalues; Entropy; Heusler alloys; Hysteresis; Magnetization curves; Martensite; Martensitic transformations; Mathematical analysis; Phase transitions; Phases; Platinum; Shape memory alloys; Substitutes; Transition layers
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.166818

•Very low thermal hysteresis across martensite transition.•Perfect geometrical compatibility between austenite and martensite.•Reversible magnetocaloric effect. 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 alloys for magnetic refrigeration and also suggest that any of the above measurement protocol can be used for the calculation of ΔSiso for materials satisfying geometrical compatibility condition.