  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.
