Structural, magnetic and transport properties of Ni-Fe-Al alloys

Melt spun ribbons (MSR) of the Ni55Fe20Al25 alloy exhibit a first-order martensitic transition (MT) in the vicinity of a second-order ferromagnetic-to-paramagnetic phase transition. Contrasted with a sharp, complete and thermoelastic MT in MSR, a partial, sluggish and non-thermoelastic MT occurs in annealed Ni55Fe20Al25 alloy that possesses a much higher degree of atomic order. However, the annealed samples have stronger local magnetocrystalline anisotropy and higher Curie temperature (TC) than MSR. Negative magnetoresistance, Δρ|/ρ, is two times larger in MSR than in the annealed case. Δρ|/ρvs. H isotherms in MSR change curvature from concave-upwards to concave-downwards as the temperature is raised through TC whereas concave-downward curvature persists over the entire temperature range in the annealed counterpart