Structure, magneto-structural transitions and magnetocaloric properties in Ni50−xMn37+xIn13 melt spun ribbons

• Published in: Journal of magnetism and magnetic materials 2012-01, Vol.324 (1), p.26-32
• Main Authors: Raj Kumar, D.M., Rama Rao, N.V., Manivel Raja, M., Sridhara Rao, D.V., Srinivas, M., Esakki Muthu, S., Arumugam, S., Suresh, K.G.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Exchange and superexchange interactions; Inverse magnetocaloric effect; Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.); Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetocaloric effect, magnetic cooling; Martensite; Martensitic transformations; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2011.07.022

Melt spun Ni50−xMn37+xIn13 (2≤x≤5) ribbons were investigated for the structure, microstructure, magneto-structural transitions and inverse magnetocaloric effect (IMCE) associated with the first-order martensitic phase transition. The influence of excess Mn in Ni site (or Ni/Mn content) on the martensite transition and the associated magnetic and magnetocaloric properties are discussed. It was found that with the increase in Mn content, the martensitic transition shifted from 325 to 240K as x is varied from 2 to 4, and the austenite phase was stabilized at room temperature. The x=5 ribbon did not show the martensitic transition. For the x=3 ribbon, the structural and magnetic transitions are close together unlike in the x=4 ribbon in which they are far (∼60K) apart. The zero field cooled and field cooled curves support the presence of exchange bias blocking temperature due to antiferromagnetic interactions in the ribbons. A large change in the magnetization between the martensite and austenite phases was observed for a small variation in the Ni/Mn content, which resulted in large IMCE. A large positive magnetic entropy change (ΔSM) of 32J/kgK at room temperature (∼ 300K) for a field change of 5T with a net refrigeration capacity of 64J/kg was obtained in the Ni47Mn40In13 ribbon. ► The increase in Mn content stabilizes the austenite phase at RT, with a marginal decrease in exchange blocking temperature. ► The lattice parameter above the critical value of 6Å for x=5 ribbon led to the absence of a martensitic transition. ► The structural transition temperature increases with increasing e/a ratio.