Physical Society Colloquium

Magnetic layers separated by a nonmagnetic spacer layer are not only model magnetic nanostructures exhibiting interesting physics, but are also the basis for GMR (giant magnetoresistance) sensors and the spin- valve read heads planned for the next generation of computer hard drives. The GMR and the interlayer exchange coupling of these structures are very sensitive to roughness and interdiffusion at the interfaces. Taking Fe/X/Fe(100), where X is Cr or Au, as model systems, we tried to create magnetic structures as close as possible to the theoretical ideal and then determine the departures from that ideal. We have used scanning electron microscopy with polarization analysis (SEMPA) to measure the periodic reversals of the exchange coupling in Fe/Cr/Fe(001) with increasing Cr thickness; there is good agreement with theory when account is taken of the interface roughness determined from scanning tunneling microscopy (STM) measurements. From scanning tunneling spectroscopy of Fe and Cr surface states, we also found that Cr growth on Fe(100) at a temperature that leads to layer-by-layer growth also leads to interdiffusion at the interface which explains some observed magnetic anomalies. The strength of the exchange coupling in Fe/Au/Fe(001) was determined taking account of thickness fluctuations in the Au layer; substantial agreement was found between theory and experiment in contrast to previous work.

Friday, March 6th, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112)