Magnetic vortices instead of stripes: Another interpretation of magnetic neutron scattering in lanthanum cuprates

It is proposed that a two-dimensional magnetic superstructure closely related to the one mentioned recently by Christensen constitutes a viable interpretation of the fourfold splitting of the magnetic (pi,pi) peak in lanthanum cuprates. (This splitting is usually interpreted as evidence for stripes.) The superstructure in question has the topology of a square crystal of magnetic vortices with approximate periodicity 4ax4a. This vortex crystal exhibits no magnetic antiphase lines. It is shown that such a superstructure is magnetically stable in the approximation of staggered spin polarizations and that it should be accompanied by charge modulation characterized by charge peaks at the positions observed experimentally.