Giant magnetoresistance in 60–150-nm-wide pseudo-spin-valve nanowires

Abstract

The magnetic and magnetotransport properties exhibited by arrays of 60–150-nm-wide pseudo-spin-valve (PSV) nanowires have been investigated. The starting PSV thin film consisted of sputtered NiFe (6 nm)/Cu(3.7 nm)/Co(3 nm)/Cu(3 nm), exhibiting a room temperature giant magnetoresistance (GMR) ratio of 2.5%. Large area arrays of 150-, 80-, and 60-nm-wide nanowires were patterned from this PSV film using a combination of interference lithography and ion milling. The effects of reducing the width of the wires are a monotonic decrease in the GMR ratio and the saturation magnetization, and an increase of both the resistivity of the wires and the average switching fields of the magnetic layers. On cooling the samples to 77 K, the resistivity decreases slightly and the GMR amplitude increases independently of the width of the wires. These results suggest the presence of a disordered region at the edges of the wires as a result of processing, which increases the resistivity and decreases the saturation magnetization as the wire width decreases.