Magnetic Properties of Ultrathin Laminated Co/Cu Films Prepared by Electrodeposition

The magnetic properties of a series of electrodeposited [ Co ( x ML ) / Cu ( 17 ML ) ] 100 multilayers have been examined as a function of the cobalt layer thickness. The multilayers were grown on Si(100) covered with a highly textured Cu(100) seed layer. Films with a cobalt layer thickness less than x < 1.7 monolayer equivalents (ML) exhibit superparamagnetic behavior due to the finite size of the cobalt islands comprising the discontinuous multilayer structure. In contrast, in films with x > 1.7 ML the lateral length scale becomes large enough to stabilize ferromagnetism and the giant magnetoresistance effect is observed. The influence of magnetocrystalline anisotropy is not apparent until 2.5 > x > 3.7 ML . The coercivity increases between 1.6 and 9 ML, reflecting the combined influence of the magnetocrystalline anisotropy and surface roughness.