MAGNETOSTRICTION AND MAGNETIC-PROPERTIES OF IRON-COBALT ALLOYS MULTILAYERED WITH SILVER

Commercially available Fe-Co alloys with Co contents of 50 and 24 wt. % have been rf sputtered to produce multilayers with noble metal (Ag o r Cu) interlayers. Series with fixed Fe-Co or noble metal thicknesses have been produced, as have plain Fe-Co films. In all cases, the coerc ivities of the multilayers are significantly reduced from those exhibi ted by the plain alloy films. For example, a film of the alloy contain ing 50 wt. % Co had H-c=6.9 kA m(-1), whereas a multilayer with 12 nm Fe-Co layers and 2 nm Ag layers had H-c=480 A m(-1). The saturation ma gnetostriction is also enhanced, in some cases increasing by 60% over the expected bulk polycrystalline alloy value. For example, the litera ture lambda(s) value for a Fe-Co alloy containing 24% Co is about 28 p pm; in a multilayer with 12 nm alloy layers and 8 nm Ag layers, lambda (s)=45 ppm. The combination of high magnetostriction and low coercivit y makes such materials as these attractive for their potential as stre ss sensor and actuation transducer elements.