Probing antiferromagnetic domains and textures at criticality using single-shot Resonant Coherent Soft X-ray Scattering

Strongly correlated oxides host a rich phase diagram due to the strong interplay between structural, electronic and spin degrees of freedom. For example, the perovskite nickelate compound PrNiO3 (PNO) exhibits a first-order phase transition from paramagnetic metal to bond-ordered antiferromagnetic insulator, in which structural, charge and spin degrees of freedom are all coupled. Here we investigate a thin film of PNO grown on a substrate of tensile-strain inducing (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT), and use coherent resonant soft x-ray scattering at the Ni L3 edge to study the emergence of the magnetic order parameter in the critical regime of the phase transition. We observe a small-q periodic modulation on the magnetic bragg peak which we argue to be the ‘fingerprint’ of a particular domain configuration. By analyzing the symmetry of these small-q modulations it was possible to directly guess the corresponding real-space domain arrangement and reproduce the observed diffraction patterns. This process is facilitated by the 2-dimensional nature of the domain arrangement, and represents a powerful new approach to single-shot imaging of 2-dimensional mesoscopic antiferromagnetic spin textures.