Laser-Induced 90-Degree Magnetization Switching for Single-Element 2D Sensing

Magnetoresistive sensors with multiaxial sensitivity are interesting for field mapping applications where local measurement of multiple magnetic field components is needed. Existing device designs are often discretized with separate sensing elements for each vector component, or they require complex detection schemes to distinguish the different components. In this work, we showcase a single-element two-dimensional vector sensor with on-demand reprogrammable sensing axis using light and optically switchable materials. Our device is an anisotropic magnetoresistive sensor with $90^\circ$ togglable sensitivity upon excitation with ultrashort laser pulses. The sensor consists of an optically switchable Co/Gd thin-film bilayer, patterned into a cross shape that stabilizes two orthogonal in-plane magnetization directions. By selectively addressing one diagonal of the cross, a single laser pulses toggle switches the magnetization direction in the center of the cross by $90^\circ$. Moreover, the field sensitivity of the device is toggled between the $x$- and $y$-axes, which we detected electrically with the planar Hall effect. Our results form a milestone towards optically reprogrammable integrated magnetic vector sensors.