Antiferromagnetic domain structure in bilayer manganite

We report a soft x-ray nanodiffraction study of antiferromagnetic domains in the strongly correlated bilayer manganite La sub(0.96)Sr sub(2.04)Mn sub(2)O sub(7). We find that the antiferromagnetic domains form a unique domain pattern with each domain having an intrinsic memory of its spin direction. This can be explained by the presence of crystallographic or magnetic imperfections locked in during the crystal growth process which pin the antiferromagnetic domains. The antiferromagnetic domain pattern shows two distinct types of domain. One of the domain types was observed to contain a periodic ripple in the manganese spin direction with a period of approximately 4 mu m. We propose that the loss of inversion symmetry within a bilayer is responsible for this ripple structure through a Dzyaloshinskii-Moriya-type interaction.