Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Abstract

We study layered synthetic antiferromagnets (SAFs) with out-of-plane interface anisotropy, where the layer-wise antiferromagnetic (AF) alignment is induced by interlayer exchange coupling (IEC). By applying low energy He+ focused ion beam irradiation to the SAF, a depth-dependent reduction of the IEC and anisotropy can be achieved due to layer intermixing. As a consequence, after irradiation, a specific field reversal sequence of the SAF is energetically preferred. When tuning the pristine SAF to exhibit an inverted field reversal, we are thus able to create AF domains in the irradiated regions. When irradiated with a fluence gradient, these AF domains can be further deterministically manipulated by an external magnetic field. Among other applications, this could be utilized for engineering a controllable and local magnetic stray field landscape, for example, at AF domain walls, within the otherwise stray field free environment provided by the SAF.