Antiferromagnetic real-space configuration probed by x-ray orbital angular momentum phase dichroism

X-ray beams with orbital angular momentum (OAM) are a promising tool for x-ray characterization techniques. Beams with OAM have an azimuthally varying phase, and new material properties can potentially be probed by utilizing this unique phase structure. Here, we show how OAM beams are created through resonant diffraction from an artificial antiferromagnet with a topological defect. The scattered OAM beams have circular dichroism whose sign is coupled to the phase of the beam [1]. Using magnetic scattering calculations, we show that this dichroism is related to the real-space configuration of the antiferromagnetic ground state. Thermal cycling of the artificial antiferromagnet can change the ground state, as indicated by the changing phase dichroism. These results exemplify the potential of OAM beams to probe matter in a way that is inaccessible using currently available x-ray techniques.

[1] M. R. McCarter et al. arXiv:2205.03475 (2022).