Structural evolution and giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers

Abstract

Structural transformations and their effect on giant magnetoresistance (GMR) were investigated in electrodeposited Co/Cu multilayers with varying Co-layer thicknesses $({t}_{\text{Co}})$ in the range of 0.2--10 nm while keeping the Cu layer thickness $({t}_{\text{Cu}})$ fixed at 4 nm. X-ray diffraction, scanning electron microscopy, cross-sectional transmission electron microscopy, and magnetization measurements were carried out to probe the structural transition from granular to semicontinuous to continuous Co layers. An unexpected result of the study is the observation of variations in GMR characteristics with a sharp peak in GMR at ${t}_{\text{Co}}=0.5\text{ }\text{nm}$ followed by a broad peak at ${t}_{\text{Co}}=3\text{ }\text{nm}$. The GMR results have been analyzed in terms of ferromagnetic and superparamagnetic components for samples with varying ${t}_{\text{Co}}$ to understand the structural evolution of the magnetoresistance behavior.