Residual stress optimization in FeAlN pole materials

Abstract

RF-diode reactively sputtered FeAlN films, which are good candidates for high-density write head pole materials, usually have very large compressive residual stresses. In this paper we describe our efforts to lower the residual stress, and study the effects of lowered stress on the magnetic properties of the FeAlN films. It is found that increasing the total sputtering pressure while keeping the optimum Fe to N arrival flux ratio constant can lower the residual stress. The films with lowered residual stress, however, are more susceptible to the formation of stripe domains, which are detrimental to the magnetic properties. In order to avoid these stripe domains, the thickness of the film should not exceed the critical stripe domain onset thickness. For applications where thicker films are desired, we demonstrate that laminating single layer films whose thicknesses do not exceed the critical thickness produces films with good magnetic properties and acceptable residual stress.