Analysis of magnetocaloric effect of ball milled amorphous alloys: Demagnetizing factor and Curie temperature distribution

• Demagnetizing field significantly affect the field dependence of MCE.
• M(H) is corrected using N = 1/3 recovering the theoretical behavior for powder samples.
• Differences between ball-milled and melt-spun samples are due to a distribution of Tc.
• Simulations using Arrot–Noakes equation of state confirm our hypothesis.

The magnetocaloric effect (MCE) has been measured for an amorphous mechanically alloyed (MA) Co62Nb6Zr2B30. It is demonstrated that sample shape must be taken into account for a correct interpretation of the results, especially to correctly determine the field dependence of magnetic entropy change and refrigerant capacity. However, although correcting the influence of the demagnetizing factor allows us to recover the theoretically predicted behavior for these field dependencies, they differ from those obtained for a rapidly quenched (RQ) amorphous alloy of the same composition. This deviation is assigned to a broader Curie temperature distribution in MA alloys with respect to RQ alloys. Theoretical simulations based on the Arrott–Noakes equation of state and a Gaussian distribution of TC support this hypothesis.