Magnetoresistance and surface roughness study of the initial growth of electrodeposited Co/Cu multilayers

TL;DR

This study investigates the initial growth, surface roughness, and magnetoresistance properties of electrodeposited Co/Cu multilayers with thicknesses up to 70 nm, focusing on early-stage microstructure development and magnetic behavior.

Contribution

It extends previous research by analyzing ultrathin Co/Cu multilayers, examining surface roughness, electrical transport, and magnetoresistance during initial growth stages with various layer configurations.

Findings

Surface roughness increases with layer thickness.

Magnetoresistance behavior reveals formation of superparamagnetic regions.

Layer nucleation and exchange reactions influence microstructure evolution.

Abstract

The giant magnetoresistance (GMR) effect has been widely investigated on electrodeposited ferromagnetic/non-magnetic (FM/NM) multilayers generally containing a large number of bilayers. In most applications of the GMR effect, layered structures consisting of a relatively small number of consecutive FM and NM layers are used. It is of great interest, therefore, to investigate the initial stages of GMR multilayer film growth by electrodeposition. In the present work we have extended our previous studies on ED GMR multilayers to layered structures with a total thickness ranging from a few nanometers up to 70 nm. The evolution of the surface roughness and electrical transport properties of such ultrathin ED Co/Cu layered structures was investigated. Various layer combinations were produced including both Co and Cu either as starting or top layers in order (i) to see differences in the nucleation of the first layer and (ii) to trace out the effect of the so called exchange reaction. Special attention was paid to measure the field dependence of the magnetoresistance, MR(H) in order to derive information for the appearance of superparamagnetic regions in the magnetic layers. This proved to be helpful for monitoring the evolution of the layer microstructure at each step of the deposition sequence.