Effect of annealing on the magnetic, magnetocaloric and magnetoresistance properties of Ni-Co-Mn-Sb melt spun ribbons

TL;DR

This study investigates how annealing affects the structural, magnetic, magnetocaloric, and magnetoresistance properties of Ni-Co-Mn-Sb melt spun ribbons, highlighting improvements in properties relevant for magnetic refrigeration applications.

Contribution

It demonstrates that annealing induces atomic ordering changes in melt spun ribbons, significantly altering their functional magnetic properties and reducing hysteresis loss for practical magnetic refrigerant use.

Findings

Annealing transforms the B2 phase to L21 phase, enhancing properties.

Significant changes in magnetocaloric effect and magnetoresistance observed.

Hysteresis loss can be reduced through controlled annealing.

Abstract

The structural, magnetic, magnetocaloric and magnetotransport properties of Ni46Co4Mn38Sb12 melt spun ribbons have been systematically investigated. The partially ordered B2 phase of the as-spun ribbon transforms to fully ordered L21 phase upon annealing, which signifies a considerable change of the atomic ordering in the system. The presence of atomic disorder in the as-spun ribbon gives rise to a higher martensitic transition temperature and a lower magnetization as compared to the bulk sample. However, annealing the ribbons helps in regaining the bulk properties to a large extent. Significant changes in magnetocaloric effect, exchange bias and magnetoresistance have been observed between the as-spun and the annealed ribbons, indicating the role of atomic ordering on the functional as well as fundamental properties in the Heusler system. Importantly, the study shows that one can reduce the hysteresis loss by preparing melt spun alloys and subjecting them to appropriate annealing conditions, which enable them to become practical magnetic refrigerants.