An extraordinary chiral exchange-bias phenomenon: engineering the sign of the bias field in orthogonal bilayers by a magnetically switchable response mechanism.

Isothermal tuning of both the magnitude and the sign of the bias field has been achieved by exploiting a new phenomenon in a system consisting of two orthogonally coupled films: SmCo5 (out-of-plane anisotropy)-CoFeB (in-plane anisotropy). This has been achieved by using the large dipolar magnetic field of the SmCo5 layer resulting in the pinning of one of the branches of the hysteresis loop (either the ascending or the descending branch) at a fixed field value while the second one is modulated along the field axis by varying the orientation of an externally applied magnetic field. This means the possibility of controlling the sign of the bias field in a manner not reported to date.

Emergence of the Stoner-Wohlfarth astroid in thin films at dynamic regime.

The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the magnetization reversal of nanoscale systems that are small enough to contain single magnetic domains. However for larger sizes where multi-domain effects are present, e.g.

Direct observation of temperature-driven magnetic symmetry transitions by vectorial resolved MOKE magnetometry.

Angle- and temperature-dependent vectorial magnetometry measurements are necessary to disentangle the effective magnetic symmetry in magnetic nanostructures. Here we present a detailed study on an Fe(1 0 0) thin film system with competing collinear biaxial (four-fold symmetry) and uniaxial (two-fold) magnetic anisotropies, carried out with our recently developed full angular/broad temperature range/vectorial-resolved magneto-optical Kerr effect magnetometer, named TRISTAN. The data give direct views on the angular and temperature dependence of the magnetization reversal pathways, from which characteristic axes, remanences, critical fields, domain wall types, and effective magnetic symmetry are obtained.