Abstract
Two dimensional arrays of amorphous R-Co (R = Sm and Gd) alloys or Fe, Ni, alloys with thickness around 200 urn were prepared on top of a 20 nm thick niobium film by means of a-beam lithography and sputter deposition. The arrays consist of 2×2μm2 square particles with spatial periodicity ranging from 4 to 8 μm along the edge of the squre. Demagnetizing processes, magneto optical properties and transport properties were studied. The demagnetization curves appeared strongly different from those of bulk films with no pattern. The obtained curves were compared to those predicted by computor simulation. Calculations show that the evolution of dipolar fields leads to successive reversal of the particles column by column. When these arrays were illuminated by a laser beam, a set of Bragg reflections was observed. The obtained diffraction hysteresis loops were found to yield novel information about the domain structure on a submicron scale. Interesting oscillations due to the fluxoid quantization were observed in the transition lines of underlying Nb films. The superconducting state of the Nb is modulated by stray fields by the square magnetic particles.
