Martensite transformation and magnetic properties of Ni50Mn25Ga25- xFe x ferromagnetic microwires for application in microdevices.

Ni50Mn25Ga25- xFe x (1 ≤ x ≤ 6) microwires with a diameter of 30-50 µm were prepared by melt-extraction. The effects of Fe doping on the martensite transformation temperature, Curie point and magnetic properties before and after chemical ordering treatments were investigated. Experimental results show that Ni50Mn25Ga25- xFe x microwires exhibit typical thermoelastic martensite transformation and magnetic transition. Transformation temperatures of the microwires increase with Fe content with a rate of 27.3 K/at%. Thermal hysteresis during martensite transformation is lowered after Fe doping. The Curie point of Ni50Mn25Ga25- xFe x (1 ≤ x ≤ 6) microwires keeps stable at 390 K, which is 25 K higher compared with Ni2MnGa ternary alloy. After chemical ordering heat treatment, the microwires exhibit a typical ferromagnetic transition and a higher saturation magnetization at low field compared to as-extracted microwires. [ABSTRACT FROM AUTHOR]