Magnetocaloric Behaviour in Amorphous and Nanocrystalline FeNbB Soft Magnetic Alloys

Abstract

We have studied the temperature dependence of the magnetocaloric effect in series of amorphous and nanocrystalline Fe_80.5Nb₇B_12.5 melt-spun ribbons. The maximum entropy change ΔS_m ≈ 0.72 J/kgK is found at the Curie temperature of the amorphous material, T _C(am) ≈ 363 K, upon a 0.7 T magnetic field change. This ΔS_m value is a factor of four less than that of gadolinium, the prototypical high-temperature magnetocaloric material, but it compares favorably with other amorphous Fe-based alloys. The progressive nanocrystallization of amorphous ribbons results in a decrease of magnetic entropy change and at the same time the ΔS_m peak becomes broadened.