For the first time, researchers from Arizona State University, IBM Almaden Research Labs and Lawrence Berkeley Laboratory's Advance Light Source collaborated to show that the alignment between electron spins are colinear across an AFM and FM interface. Exchange bias occurs when the exchange coupling of ferromagnetic and anti-ferromagnetic films across their common interface causes a shift in the hysteresis loop of the ferromagnet. The effect was first discovered in 1956, although its origin was never confirmed. Since then, physicists have tried to understand how the arrangement of spins at interfaces in a layered magnetic material affects the properties of that material.
Exchange bias is useful in controlling the magnetization in heads used in magnetic disk storage.
Today nearly all hard drives use anti-ferromagnets in the reader head. Michael R. Scheinfein, a physics professor at Arizona State University and one of the paper's authors, said by using a polarized x-ray magnetic dichroism spectromicroscopy that separately revealed the micromagnetic structure on both sides of the interface, it was possible to confirm an AFM and FM colinear alignment. The results also demonstrate the usefulness of spectromicroscopy for determining the micromagnetic structure on each side of interfaces in thin films.