Glass formation ability, structure and magnetocaloric effect of a heavy rare-earth bulk metallic glassy Gd 55Co 20Fe 5Al 20 alloy

Abstract

The glass formation ability, the structure and the magnetocaloric effect of the bulk metallic glassy Gd 55Co 20Fe 5Al 20 alloy were investigated. Bulk metallic glassy (BMGs) alloys were prepared by a copper-mold casting method. The glass forming ability and their structure were studied by using X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The XRD analysis revealed that the as-cast cylinder of Gd 55Co 20Fe 5Al 20 alloy showed fully amorphous structure in 2 mm diameter. The DSC revealed that the bulk cylinder of the Gd 55Co 20Fe 5Al 20 alloy showed a distinct glass transition temperature and a relatively wide supercooled liquid region before crystallization. SQUID investigated the magnetic properties and the entropy changes. The Curie temperature of Gd 55Co 20Fe 5Al 20 BMGs alloy was about 130 K, but the maximum magnetic entropy changes(−Δ S M) showed at about 125 K, a little lower than the Curie temperature 130 K. The reason could probably be due to the presence of a little amount of nanocrystalline particles between amorphous phases. The BMG alloy has the characteristic of second-order transition (SOT) on Arrott plots. The results showed that the amorphous sample had a relatively improved magnetocaloric effect, indicating that the amorphous alloy could be considered as a candidate for magnetic refrigeration applications in the temperature interval range of 100–200 K.