Phase formation and magnetocaloric effect in rapidly quenched La(Fe1−xCox)11.4Si1.6

Abstract

The effect of Co content on the phase formation, structure, and magnetocaloric effect of rapidly quenched La(Fe1−xCox)11.4Si1.6 with x=0 to 0.12 were investigated by x-ray diffractometry and magnetic measurements. Rietveld analyses indicate that with increasing Co content, the amount of the 1:13 phase increases from about 22 to 62 wt. % in the rapidly quenched alloys. A very short time annealing (1273K∕20min) of the as-quenched alloy is sufficient for the formation of a single phase 1:13 structure. The peak value of the magnetic entropy change is 20.5,11.8,9.9J∕kgK for the annealed rapidly quenched compounds with x=0, 0.04, and 0.08, respectively. Increasing Co content drives the order of magnetic transition, near TC, from first order to second order and eliminates the occurrence of the field-induced magnetic transition above TC, which is responsible for the decrease in the magnetocaloric effect.