Improving exchange-spring magnets with interfacial modification.

Using magnetic thin film multilayers as model exchange-spring systems proves to be the promising intellectual path that helps generate the mechanistic and materials insights needed to create high-performance permanent magnet materials. We demonstrate a new route to improve exchange-spring magnets whereby the hard/soft interface in epitaxial Sm-Co/Fe and Sm-Co/Co bilayer thin film structures is modified via thermal processing. The effect of thermal processing is modeled with a graded interfacial region across which the material parameters vary linearly. We discuss the mechanism for improved exchange-spring behavior and the implication on magnet processing toward realizing the full potential of the exchange-spring principle