Magnetoresistance and magnetic force microscopy studies in Ni[sub 80]Fe[sub 20] disk- and ring-patterned wires.

We have investigated the magnetization reversal process of the disk-, ring-, and center dot ring-patterned Ni[SUB80]Fe[SUB20] wires. For the fields applied perpendicular to the wire direction, interesting shape dependent magnetoresistance (MR) ratios were found. The MR ratios were varied from 0.8%, 0.65%, and 0.4% at room temperature and 1.7%, 1.5%, and 1.1% at 10 K for the disk-, ring-, and center dot ring-patterned wires. For the same wires, the switching field is reduced from -170, -110, and -90 Oe at room temperature to -140, -70, and -20 Oe at 10 K. These results were due to the shape anisotropy and domain-wall motion. The anisotropy MR (AMR) ratios measured at 10 K of the disk-, ring-, and center dot ring-patterned wires were 1.9 ± 0.1%, 1.7 ± 0.1%, and 1.3 ± 0.1%, respectively, it is almost even the same (1.1 ± 0.1%) at room temperature. We have observed that the center dot reduces the MR ratio and increases magnetic saturation field of the Ni[SUB80]Fe[SUB20] wires. [ABSTRACT FROM AUTHOR]