Abstract
Since the discovery of the giant-magneoresistance (GMR) effect (1) in magnetic thin film structures, giant-magneoresistance spin-valve structures have been promising candidates for high-density magnetic recording read head sensors. A significant concern for the performance of these read head sensors is the thermal stability. Long-term operation under a high current density causes thermal degradation and interdiffusion of multilayers. Previous studies of the effect of annealing on the spin-valve multilayers were carried out using X-ray reflectivity (2) and nuclear magnetic resonance (NMR) (3). However in most studies, they only offered the average of interface mixing over the film plane. The microstructure information plays an important role in the diffusion mechanism of the spin-valve structure. In viewpoint of microstructure, the major concerns in spin-valve multilayers are the identity of the phases, the texture, the grain size, the roughness of the individual layer, and the interfacial structure between each layer. In our work, we used a field emission gun transmission electron microscope (FEGTEM) with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) to investigate the microstructure and composition distribution of the spin-valve ultra thin film structures.