Giant magnetoresistivity in electrochemically produced cobalt-copper multilayers

The electrodeposition of cobalt-copper multilayers will be described and the dependence of their magnetoresistivity on layer thickness and deposition parameters will be presented. For a wide variety of layer thicknesses electrochemically produced Co(Cu)-Cu thin polycrystalline layered alloys exhibit a giant magnetoresistivity (GMR). Further, upon annealing, the materials undergo a combination of grain growth and grain boundary diffusion. At certain conditions, this phenomena is believed to lead to a break up of the layered structure so that a magnetostatic coupling occurs and contributes to the GMR behavior. It is further shown that, by careful control of the deposition parameters, a quasilinear GMR response (low sensitivity) can be created over a large magnetic field or, conversely, a high sensitivity material can be grown, although at the sacrifice of introducing hysteresis in the response curve. The major deposition parameter affecting this behavior is mass transport in the electrolyte; however, substrate grain size, layer spacing and annealling history also play an important role.