Magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys

Abstract

A study of magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys is reported. Amorphous Fe40Ni38Mo4B18, near its magnetic ordering temperature (600K) showed a magnetic entropy change ΔSM of 1.1 J/KgK and a relative cooling power of 36J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperature of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27J/kgK near the magnetic ordering temperature of the amorphous matrix (540K) in a field change of 10 kOe. The decrease in ΔSM on partial crystallisation is attributed to the biphasic magnetic nature of the sample.

Iron and manganese based magnetocaloric materials for near room temperature thermal management

“…Alloying of Fe-Ni with 5% of Cr reduced the TC significantly, from ~ 443 K to 258 K, the RCP value is 406 Jkg -1 ; higher than those of Gd nanoparticles (400 Jkg -1 ), at Δµ0H of 5 T. A maximum |∆SM| of 1.8 Jkg -1 K -1 at ~ 125 K for a field change of 5 T was observed in a γ-Fe49Ni29Cr22 alloy [75]. Jkg -1 K -1 and a RCP of 36 Jkg -1 for a field change of 1 T at 600 K [77].…”