T=0 phase diagram and nature of domains in ultrathin ferromagnetic films with perpendicular anisotropy

SANTIAGO A. PIGHÍN; ORLANDO V. BILLONI; DANIEL A. STARIOLO; SERGIO A. CANNAS

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2010 vol. 322 p. 3889 - 3894

0304-8853

We present the complete zero temperature phase diagram of a model for ultrathin films withperpendicular anisotropy. The whole parameter space of relevant coupling constants isstudied in first order anisotropy approximation. Because the ground state is known tobe formed by perpendicular stripes separated by Bloch walls, a standard variationalapproach is used, complemented with specially designed Monte Carlo simulations.We can distinguish four regimes according to the differentnature of striped domains: a high anisotropy Ising regime with sharp domain walls, asaturated stripe regime with thicker walls inside which an in-plane component of themagnetization develops, a narrow canted-like regime, characterized by a sinusoidal variation of boththe in-plane and the out of plane magnetization components, which upon further decrease of theanisotropy leads to anin-plane ferromagnetic state via a spin reorientation transition (SRT). The nature ofdomains and walls are described in some detail together with the variation of domainwidth with anisotropy, for any value of exchange and dipolar interactions. Our results,although strictly valid at T=0, can be valuable for interpreting data on the evolutionof domain width at finite temperature, a still largely open problem