Exchange Bias in Nanostructures: An Update

Abstract

Exchange bias (EB) is a unidirectional anisotropy occurring in exchange-coupled ferromagnetic/antiferromagnetic systems, such as thin films, core–shell particles, or nanostructures. In addition to a horizontal shift of the hysteresis loop, defining the exchange bias, asymmetric loops and even vertical shifts can often be found. While the effect is used in hard disk read heads and several spintronics applications, its origin is still not fully understood. Especially in nanostructures with their additional shape anisotropies, interesting and often unexpected effects can occur. Here, we provide an overview of the most recent experimental findings and theoretical models of exchange bias in nanostructures from different materials.

Modeling the Training Effect in Exchange‐Biased Bilayers for Large Numbers of Magnetization Reversal Cycles

“…[1,2] It occurs typically in ferro-/antiferromagnetic (FM/AFM) thin film systems or nanostructures after cooling in the presence of magnetic field (so-called field-cooling) the system through the Néel temperature of the AFM, while there are also several systems containing ferrimagnets as one of the components, or even single-phase materials, in which surface effects result in an EB. [3,4] The most prominent feature is a horizontal shift of the hysteresis loop, usually opposite to the cooling field direction. However, there are also reports about a broadening of the hysteresis loop, a vertical loop shift, or an asymmetry of the loop.…”