Study on exchange bias effect in Fe/Cr(100) bilayers

Abstract

Understanding the exchange bias mechanism at the interface between a ferromagnet (FM) and an antiferromagnet (AFM) has been an almost half-century old problem after first discovery by Meiklejohn and Bean, who found that fine nanoparticles of partially oxidized Co exhibit magnetization curves with an unusual displacement along the field axis, as though there were a bias field in addition to the applied field. Tremendous efforts have been devoted to clarify the physics of the exchange bias effect since the exchange-biased system provides us a new kind of intriguing physical system having an interface between two dissimilar ordered magnetic systems as well as promising applications to spin-valve devices such as magnetic random access memory. Despite its technical importance, the exact origin involving these phenomena has not yet been clarified and remains a major outstanding problem in thin film magnetism. This is mostly attributed to the fact that the spin structure at the FM/AFM interface is complex and the kind of exchange interaction is completely unknown. Therefore, it is essential to investigate systematically the exchange-biased system with a well-defined spin structure and an exchange interaction between FM and AFM spins at the FM/AFM interface. For this purpose, we have chosen a Fe(FM)/Cr(AFM) bilayer system since their magnetic properties have been fairly well characterized through various previous experimental researches done over the last decade but there has been no report about the exchange bias effect in this systems. Transition metal Cr is an itinerant antiferromagnet very different from other kinds of oxide-antiferromagnets, etc., such as NiO and CoO or metallic-antiferromagnet such as MnFe and MnIr, etc., which most researchs have been focused on so far. we have systematically investigated the magnetic properties of the Fe/Cr(100) bilayer structure with varying temperatures or cooling fields using the superconducting quantum interference de-vice ...