Atomic Scale Structure of Giant Magnetoresistive Multilayers: Energetic Adatom and Surfactant Effects

–The deposition of higher quality giant magnetoresistive (GMR) metal multilayers is essential for improving the performance of magnetic field sensors and nonvolatile random access memories. Improved performance requires reduction of both the atomic scale interfacial roughness and interlayer mixing in the as deposited films. The first step is to develop relationships between controllable process parameters and the atomic scale interfacial composition/structure. We have used atomistic simulation and controlled experiments to begin to address this issue. We show that control of the adatom energy and the use of a silver surfactant can improve the interface structure of multilayers. Increasing the adatom energy causes surface flattening due to enhanced surface reconstruction, but results in interlayer mixing due to impact induced atomic exchanges. A modulated energy deposition scheme was found to reduce both roughness and mixing. The addition of a small quantity of silver was found to reduce the activation barriers for surface atomic assembly and to enable the assembly process kinetics to be shifted to a regime where conventional deposition processes are able to create high quality interfaces.