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 80.5 Nb 7 B 12.5 melt-spun ribbons. The maximum entropy change ∆S m ≈ 0.72 J/kgK is found at the Curie temperature of the amorphous material, TC(am) ≈ 363 K, upon a 0.7 T magnetic field change. This ∆Sm 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 ∆Sm peak becomes broadened.

The Magnetocaloric Effect and Magnetic Refrigeration Near Room Temperature: Materials and Models

“…1 Previous results regarding the MCE of superparamagnetic nanoparticles (154)(155)(156) led researchers in the field of soft magnetic nanocrystalline alloys to think that the transition from ferromagnetism (at temperatures below the Curie temperature of the matrix, T am C ) to superparamagnetism (at temperatures above T am C , high enough to prevent the interactions between the nanocrystals) could give rise to good magnetic refrigerants. Therefore, there were several attempts to study the magnetocaloric response of soft nanocrystalline alloys of the Finemet and Nanoperm families, with different alloying elements to tune T am C close to room temperature, but results for S M were less favorable than those for the paradigmatic Gd (157)(158)(159). Not only did | S M | decrease as the volume fraction of the nanocrystals increased, but also RC did not improve along the nanocrystallization process (148).…”

Investigation of the Critical Behavior, Magnetocaloric Effect and Hyperfine Structure in the Fe72Nb8B20 Powders

“…Indeed, in the amorphous Fe 93-x Nb 7 B x (x = 9, 14 and 20) prepared by rapid quenching, the entropy values are for x = 9, 14 and 20, respectively [ 17 ]. The temperature dependence of the MCE was studied in amorphous and nanocrystalline Fe 80.5 Nb 7 B 12.5 melt-spun ribbons [ 18 ]. The maximum entropy change was about , at of the amorphous phase, upon a magnetic field modification of 0.7 T. Nevertheless, the magnetic entropy variation decreased and its peak broadened with the progressive nanocrystallization of the amorphous ribbons.…”

Magnetic measurements of Fe–Ni–Nb–B and Fe–Co–Mo–Cu–B in the vicinity of the Curie temperature

“…Such materials are also interesting from the viewpoint of magnetocaloric effect [3]. The transition between ferromagnetic and paramagnetic states is accompanied by a change in most of the magnetic properties, e.g.…”