Magnetocaloric effect (MCE) in melt-extracted Ni-Mn-Ga-Fe Heusler microwires

We reported the magnetocaloric properties of Heusler-type Ni48Mn26Ga19.5Fe6.5 microwires with diameter of ∼50 μm which were fabricated by a precise melt-extraction method. The Fe-doped Ni-Mn-Ga microwires after chemical ordering heat-treatment exhibit negligible thermal and magnetic hysteresis along the axial direction due to their small magnetocrystalline anisotropy and display excellent magnetocaloric effect (MCE) for both magnetic (paramagnetic-ferromagnetic) phase transition and structural (austenite-martensite) phase transition. The maximum entropy change (−ΔSm), ∼4.7 J kg−1 K−1, is obtained during the structural transition induced by an external magnetic field of 50 kOe at a temperature of ∼361 K. Moreover, tiny positive magnetic entropy also appears when the applied field is lower than 5 kOe.