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

Abstract

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 (T_C) 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 T_C whereas concave-downward curvature persists over the entire temperature range in the annealed counterpart.