Observation of the magnetic domain structures in Cu$_{0,47}$Ni$_{0,53}$   thin films at low temperatures
  We report on the first experimental visualization of domain structure in films of weakly ferromagnetic Cu$_{0,47}$Ni$_{0,53}$ alloy with different thickness at liquid helium temperatures. Improved high-resolution Bitter decoration technique was used to map the magnetic contrast on the top of the films well below the Curie temperature T$_{Curie}$ ($\sim$ 60 K). In contrast to magnetic force microscopy, this technique allowed visualization of the domain structure without its disturbance while the larger areas of the sample were probed. Maze-like domain patterns, typical for perpendicular magnetic anisotropy, were observed. The average domain width was found to be about 100 nm. 
I.S. Veshchunov, V.A. Oboznov, A.N. Rossolenko, A.S. Prokofiev, L.Ya.   Vinnikov, A.Yu. Rusanov and D.V. Matveev