Magnetocaloric effect in LaFe11.8-xCoxSi1.2 melt-spun ribbons

The structure and magnetic entropy changes in melt-spun and annealed LaFe11.8-xCoxSi1.2 (x=,0.4 and 0.8) ribbons have been investigated. It is found that the value of Tc can be increased continuously up to 290K for x=0.8 and the phase transition, at Tc from paramagnetic to ferromagnetic, is changed from first- to second-order due to Co substitution. Large values of the magnetic entropy change are 31 and 13.5J/kgK in the magnetic field change from 0 to 5T at 201K for the LaFe11.8Si1.2 and at 290K for the LaFe11Co0.8Si1.2 ribbons, respectively. The magnetic entropy change in the LaFe11Co0.8Si1.2 ribbons is higher than that reported in the bulk counterpart and that of conventional MCE materials, such as pure Gd. The enhanced magnetic entropy change of ribbons compared to bulk counterpart is attributed to a more uniform microstructure and element distribution resulting from the high cooling rate by melt-spinning.