High-temperature magnetocaloric effect in devitrified Fe/Co based glassy monolayer and bilayer ribbons

Rapidly quenched Co- and Fe-based monolayer and their bilayer prepared through double nozzle technique have been characterized to investigate its microstructural and magnetic properties and their possibility as high-temperature magnetocaloric material. The Co- and Fe-based monolayer ribbons displayed Curie temperatures (T-C) of 463K and 700K, respectively. Magnetic entropy change S-M of the bilayer was measured at a low magnetizing field of 1T in the temperature spans covering separately for T-C of Co- and Fe-based ribbons corresponding to separate entropy at low- and high-temperature regime. The S-M value at T-C of Fe-based ribbon displayed values in the span of 1.13-1.71Jkg(-1)K(-1) in their monolayer and bilayer state. On incipient nanocrystallisation at 773K, the S-M and refrigerant capacity (RC) around T-C of cobalt-based bilayer ribbon revealed comparable values as in their as-quenched state. However, nanocrystallisation elevated the S-M of bilayer across T-C of the Fe-based regime to a high value close to 4.6Jkg(-1)K(-1) with a fairly elevated RC of 96Jkg(-1). The enhanced S-M associated with the formation of Fe-based nanocrystallites is evidenced through transmission electron microscopy. The interdiffusion of ferromagnetic elements Fe and Co is also supposed to elevate the S-M as well as the RC of the glassy system in the bilayer ribbons.