SIZE AND SELF-FIELD EFFECTS IN GIANT MAGNETORESISTIVE THIN-FILM DEVICES

Giant magnetoresistance (GMR) was measured as a function of device siz e for patterned NiCoFe/Cu and NiFe/Ag films. For the quasi-granular Ni CoFe/Cu films, the normalized maximum change in resistivity Delta rho/ rho was 8% for most of the samples. For the NiFe/Ag films, antiparalle l alignment was achieved through magnetostatic coupling, not exchange fields, with a Delta rho/rho of 4.5%. The films were patterned into st ripes with Au current leads for size-effect measurements. The height o f the stripes varied from 0.5 to 16 mu m and the track width varied fr om 1 to 16 mu m. Discrete switching events and anomalous low-field dip s in the response were observed for both materials for small device si zes. Self-field and heating effects due to the applied current were in vestigated for the NiFeCo/Cu films. The effect of the self-field produ ced by the applied current was separated from the thermal contribution and was found to reduce the response by over 32% for a current densit y of 10(7) A/cm(2).