MAGNETORESISTANCE OF THIN-FILM NIFE DEVICES EXHIBITING SINGLE-DOMAIN BEHAVIOR

Rectangular NiFe stripes as small as 1 x 5 mu m were fabricated and ch aracterized as a function of film thickness. Gold current leads were s puttered and patterned onto the stripes so that magnetoresistance meas urements could be performed. A uniform in-plane magnetic field was app lied transverse to the stripe length and at various angles from the pe rpendicular direction. For film thicknesses greater than 10 nm, the ma gnetoresistance for all of the devices had large jumps and hysteresis due to domain formation. As the thickness of the film decreased below 10 nm, the domain structure disappeared for stripe heights 2 mu m or l ess. Theoretical calculations of the magnetization reversals were obta ined using a numerical implementation of the Stoner-Wohlfarth model fo r the switching of a single-domain ellipsoidal particle. The calculati ons were used to predict the switching field where the magnetization r eaches an unstable threshold, causing a jump in the magnetization and magnetoresistance. The model was in close agreement with experimental results for various field orientations.