X-ray View of Light-Induced Spin Reorientation in TmFeO${}_3$: Direct Observation of a 90${}^{\circ }$ Néel Vector Rotation

Using time-resolved X-ray magnetic linear dichroism in reflection, we provide a direct probe of the Néel vector dynamics in TmFeO${}_3$ on a ultrafast timescale. Our measurements reveal that, following optical excitation, the Néel vector undergoes a spin reorientation transition primarily within the a-c plane, completing a full 90° rotation within approximately 20 ps. This study highlights the ability to probe dynamics of antiferromagnets at its intrinsic timescale in reflection geometry, paving the way for investigations of a wide range of antiferromagnets grown on application relevant substrates.