The following article is an edited transcript based on the MRS Medalist presentation
given by Ivan K. Schuller of the University of California, San Diego, on December 3,
2003, at the Materials Research Society Fall Meeting in Boston. Schuller received the
MRS Medal for “his innovative studies of exchange bias in magnetic heterostructures
and nanostructures.” Magnetic nanostructures have received increasing attention in
recent years, motivated by the interesting phenomena that are apparent when physical
size becomes comparable with relevant magnetic length scales. In addition, a number of
important potential applications in the sensors and storage industries have emerged.
When magnetic nanostructures are in contact with dissimilar magnetic materials, and
because their magnetic fields extend considerably outside the physical structure, they
are very susceptible to interaction with the surrounding environment. A particularly
interesting situation is a ferromagnetic nanostructure in contact with an antiferromagnetic
substrate. In this “exchange-biased” configuration, a variety of unusual
phenomena arise: The reversal mode of the ferromagnet changes considerably, the
superparamagnetic transition temperature is affected, and there is a noticeable change
in the microscopic spin configuration. A series of experiments will be described involving
these phenomena in nanostructured ferromagnets prepared by electron-beam
lithography and self-assembly.