Formation of metastable phases and their effect on the magnetic properties of Co-Cu multilayers

A series of Co-Cu multilayers with a constant Cu layer thickness of 60 Å and a Co layer thickness ranging from 12 to 90 Å, respectively, were prepared by electron beam evaporation at high vacuum. The magnetic properties and microstructure of the films and their dependences on the ferromagnetic layer thickness were investigated. It is found that Co layer grows into an fcc structure for thinner Co layer and stable hcp Co for thicker one. The fcc Co has more contributions to the magnetization than the hcp Co. Metastable Co-Cu solid solutions are formed at interfaces in all the multilayers, inducing alloying effect to reduce the magnetic moment. Lattice parameter of the Co-Cu multilayers is presented to determine the magnetic moment as a controlling parameter, and it explains above two influences successfully. The microstructure parameter, together with the microtopography characteristics, affects magnetoresistance in an inverse way.