AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI-MoM

Paper MI-MoM8
Control of Surface Roughness during Nanoscale Multilayer Deposition by Adding Surfactants

Monday, October 2, 2000, 10:40 am, Room 206

Session: Magnetic Spectroscopies
Presenter: X.W. Zhou, The University of Virginia
Authors: X.W. Zhou, The University of Virginia
W. Zou, The University of Virginia
H.N.G. Wadley, The University of Virginia
Correspondent: Click to Email
Nanoscale multilayers often exhibit special properties not possessed by their bulk constituents. For instance, multilayers composed of a thin (~20 Å) conductive layer (such as Cu) sandwiched between thin (~50 Å) ferromagnetic layers (e.g., Co) undergo a larger drop in electrical resistance under an external magnetic field. This property, called magnetoresistance, has been utilized in hard drive read heads to allow a significant increase in hard drive storage capacity, and are being explored for nonvolatile random access memories. The performance of these devices can be improved when the interfacial roughness and interlayer mixing of the multilayers can be reduced. While hyperthermal energy deposition techniques have been used to grow the nonequilibrium flat interfaces in the nanoscale multilayers, considerable interests are also growing in searching new multilayer material systems that intrinsically generate low interfacial roughness and interlayer mixing. Traditional material search criteria primarily based upon lattice-match, magnetic saturation, and thermal immiscibility resulted in high quality NiCo/Cu/NiCo multilayers. Better multilayers are likely to be formulated among more complex multilayer structures involving more elements. However, the tremendous possibilities of complex multilayer systems preclude a mere experimental trial and error search for the multilayer systems. Using an atomistic simulation approach, the effects of adding Ag and Au in the NiCo/Cu/NiCo multilayers have been explored. Remarkable Ag surface segregation and surface flattening effects were observed. These surfactant effects were found to be much less for Au. Analyses indicated that such effects can be attributed to the larger size (compared to Cu, Ni, and Co) and lower cohesive energy (compared to Cu, Ni, Co, and Au) of Ag atoms. This finding suggested a new set of materials that should be explored in experiments.