High coercivity in Co/Pt multilayers

We have found that the coercivity was increased when a Co/Pt multilayer on a Si3N4 underlayer was prepared onto a rotating substrate. A more than twofold increase in the coercivity is thought to be due to the enhancement of domain wall pinning effects caused by an increase of surface roughness in the Si3N4 underlayer. According to the results of atomic force microscopy, the surface of the Si3N4 underlayer prepared onto a rotating substrate was rougher than that of an underlayer prepared onto a stationary substrate. We believe that the enhancement of surface roughness is due to the oblique incidence of sputtered materials on the rotating substrate.