Abstract

The magnetocaloric properties of magnetic glass – coated microwires of nominal composition Ni2MnGa have been investigated. The XRD, EBSD and SEM analysis revealed the formation of single crystalline microwires whit a Cu2MnAl-type crystal structure (space group Fm-3m; cell parameter a= 5.832 Å). The metallic core thickness in microwires was estimated to be 350 µm. Hopkinson effect have been observed, which is demonstrated by a sharp increase of the magnetization just below the Curie temperature, TC. At low magnetic field values, was observed an increasing in the magnetic entropy change ∆SM(T) as a result of the Hopkinson effect. The refrigerant capacity, is higher at low magnetic field values compared with the estimated for high magnetic field values. With this regarding, the Hopkinson effect help to increase the efficiency of the magnetocaloric effect at low magnetic fields which result interesting for practical applications in magnetic refrigeration.