Abstract
Martensitic transition and magnetic response of Ni50−x Pdx,y Mn36 Sn14−y (x = 0, 1, 2 and y = 0, 1) Heusler alloys were analysed. The crystalline structure of each composition was solved by X-ray diffraction pattern fitting. For x = 1 and 2, the L21 austenite structure is formed and, for y = 1, the crystallographic phase is a modulated martensitic structure. From differential scanning calorimetry scans, we determine characteristic transformation temperatures and the entropy/enthalpy changes. The temperatures of the structural transformation increase with the addition of Pd to replace Ni or Sn, whereas the austenitic Curie temperature remains almost unvarying. In addition, the magneto-structural transition, investigated by magnetic measurements, is adjusted by suitable Pd doping in the alloys. The peak value of the magnetic entropy changes reached 4.5 J/(kg K) for Ni50Mn36Sn13Pd1 (external field: 50 kOe).
Highlights
Nowadays, the surveys of high-temperature shape memory alloys, so-called Heusler alloys, are gathering wide-reaching attention, because of their potential in developing new-fangled smart actuators with boosted purposeful properties
Among several alloys showing first-order magneto-structural transformation (FOMT), giant magnetocaloric effect (MCE) has been reported in different Ni-Mn-(Sn,In) alloys [8]
It was well-identified that in metamagnetic systems, the inverse magnetocaloric occurring on applying isothermal magnetization and adiabatic magnetization relies on field-induced reverse martensitic transformation and the cooling stems from the latent heat of the structural transformation
Summary
The surveys of high-temperature shape memory alloys, so-called Heusler alloys, are gathering wide-reaching attention, because of their potential in developing new-fangled smart actuators with boosted purposeful properties. Some Heusler alloys display mutually ferromagnetic and shape memory properties at the same time, and both effects can be tuned by temperature, pressure and/or magnetic field. Among several alloys showing first-order magneto-structural transformation (FOMT), giant MCE has been reported in different Ni-Mn-(Sn,In) alloys [8] It was well-identified that in metamagnetic systems, the inverse magnetocaloric occurring on applying isothermal magnetization and adiabatic magnetization relies on field-induced reverse martensitic transformation and the cooling stems from the latent heat of the structural transformation. We aspire to interpret the impact of the addition of non-magnetic Pd element (in Ni or Sn sites of the Heusler off-stoichiometric crystallographic structure) on the magnetic structure and the phase transformation features This will allow the control of the structural transition and the production of Ni–Mn–Sn materials with an excellent magnetic response. The influence on the crystallographic structure and transition temperatures is studied
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