Effect of oxygen incorporation on soft magnetic properties of iron-rich CoFe alloys

Abstract

The soft magnetic properties of CoFe alloys of composition between ∼74 wt% and 100% wt% Fe were investigated with particular emphasis on films within the range of 90 wt% to 100 wt% Fe. Plated films within this very high Fe alloy composition regime did not show the very low coercivity values that have been reported for bulk alloys [1] and were also expected from extrapolation to higher Fe content of data from a previous study performed at lower Fe composition [2]. Chemical analysis of the films in the present study revealed that a relatively low level of oxygen incorporation significantly changes the magnetic properties of these alloys. It has also been observed that, unlike what is typically seen for plated CoFe films of lower Fe composition [2,3], the annealing of electrodeposited CoFe alloys causes the films to become magnetically harder when the Fe content exceeds a threshold level of-95 wt% Fe. XPS analysis suggested that this increase in coercivity for electrodeposited CoFe films with alloy composition above 95 wt% Fe is caused by the formation of iron oxides or ferrites in the films.