FORC Diagrams in Magnetic Thin Films

The first-order reversal curve (FORC) technique allows the use of bulk measurements to extract nanoscale features from hysteretic systems and separate intrinsic and interaction effects. Magnetic thin films in particular possess an extremely diverse and anisotropic energy landscape, which is complicated by interactions that exist on several length scales and the effects of nonmagnetic features such as pinning defects and nucleation sites. The diversity of these energies makes magnetic thin films, heterostructures, and patterned nanostructures highly tunable and relevant to applications but also exceedingly challenging to evaluate and design. The FORC technique is a unique tool for performing these evaluations; however, the technique is often considered challenging due to a lack of accessible material on the origins of the FORC features. In response to this, this chapter presents some common FORC diagrams found in thin films and evaluates their origins using mechanistic approaches. That is, by considering specific magnetic switching events within the reversal of a magnetic system and how the magnetism evolves during the FORC measurement, key features in the FORC distribution will be developed. Establishing an understanding of the FORC distribution using this mechanistic approach expands the ability to effectively utilize the FORC technique to evaluate these complex systems.