We report evidence of spontaneous formation of a heterogeneous network of superdomains in two-dimensional square artificial spin ice nanostructures in externally applied magnetic fields. The magnetic heterogeneity is locally disordered but has a zig-zag texture at longer length scales. Resonant coherent soft-x-ray scattering off such textures give rise to unique internal structure in Bragg peaks. Our result shows that the macroscopic magnetic texture is derived from the microscopic structure of the Dirac strings.

Main text: 5 pages, 4 figures. Supplemental: 13 pages, 11 figures