Local and long-range realizations of a spin-reorientation surface phase transition

The spin-reorientation transition of an ultrathin film from perpendicular to in-plane magnetization is driven by a competition between dipole and anisotropy energies. In situ measurements of the magnetic susceptibility of Fe/2 monolayers (ML) Ni/W(110) films as a function of Fe coverage, made as the films are deposited at constant temperature, show two clear peaks that are described quantitatively as a long-range and a local realization of the …