Magnetic field-induced splitting of Bragg peaks in resonant magnetic x-ray diffraction from square artificial spin ice*

Artificial spin ice (ASI) is a class of periodic magnetic nanostructures that can display magnetic phenomena like that of natural spin ices, including analogs of magnetic monopoles. Based on the ice structure and field history, ASI systems can form a variety of energetically degenerate magnetic structures. When we probed the magnetic structure of a square ASI using spatially coherent Fe L$_3$ ($\approx$707eV) x-rays, we found that ASI Bragg peaks split when exposed to magnetic fields. This field-induced splitting is reversible: Bragg peaks display gaussian profiles in zero-field. We will present a scattering model, analogous to the theory of anti-phase domains in alloys, that reveals the magnetic structure of the square ASI necessary to create split Bragg peaks.