Ferromagnetic transition in Pd-Fe and Pd-Co alloys (abstract)

Abstract

New low-field dc magnetization measurements on dilute Pd-Fe and Pd-Co samples between 0.2 and 1.0 at. % Fe(Co) are presented. It is demonstrated that defects produced during plastic deformation and surface inhomogeneities produced during strain relieve annealing (by either preferential Pd evaporation and/or surface segregation) have a dramatic effect on the low-field response of the samples. Plastic deformation increases the Curie temperature by as much as 20%. Strain relieve anneal produces a well-defined surface layer of the order of 0.02 mm thick with a Curie temperature slightly higher than that of the bulk. This surface layer couples via dipolar forces to the bulk of the sample significantly altering the low-field response of the latter. Both effects considerably ‘‘smear’’ the magnetic transition of the samples. This explains, for example, why the low field susceptibility of ferromagnetic Pd-Co alloys never reach the demagnetization limit.1 A systematic study of the two effects will be presented and new conclusions about the ferromagnetic properties of homogeneous Pd-Fe and Pd-Co will be drawn.