Optimizing GMR spin valves: the outlook for improved properties

The current generation of giant magnetoresistance (GMR) spin valves exhibits performance characteristics which are not quite as good as desired for ultra-high-density nonvolatile memory applications. This paper addresses the scientific issues underlying the challenge of making major improvements in future generations of GMR spin valves, assesses the likelihood of making such improvements, and outlines some of the trade-offs in spin valve properties that will probably have to be made in memory applications. In our research on the underlying scientific issues, we have found that many of the magnetic and magnetoresistive properties of spin valves are strongly influenced by surface and interface effects occurring during film deposition. Some of the most important issues are the balance of surface and interface free energies, surface diffusion, interdiffusion at interfaces, low-temperature deposition, the use of surfactants to modify growth, and specular electron scattering at surfaces. In some cases, it is possible to control these factors or to use them to manipulate the growth or improve post-growth processing of spin valves to improve their magnetic and magnetoresistive properties. If research on these topics can be increased, it is very likely that major improvements can be made in the properties of future generations of GMR spin valves.