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Role of remanent domain structure and cubic anisotropy in the reorientation phase transition of ultrathin Ag/Fe/Ag(001) epitaxial films

1997; American Physical Society; Volume: 55; Issue: 17 Linguagem: Inglês

10.1103/physrevb.55.11593

1095-3795

R. P. Cowburn, J. Ferréand, J. P. Jamet, S. J. Gray, J. A. C. Bland,

Physics of Superconductivity and Magnetism

We have performed a detailed ex situ magneto-optical investigation into the magnetic properties of wedged ultrathin epitaxial Ag/Fe/Ag(001) films as a function of both temperature and Fe thickness. The Fe thickness dependent reorientation phase transition (RPT) of the magnetic easy direction from out-of-plane to in-plane has been studied at various temperatures in the range 2--180 K. By using the polar Kerr effect and the Cotton-Mouton effect in reflection we were able to probe simultaneously the out-of-plane and in-plane magnetization components. We report the thermally activated formation of an out-of-plane domain structure at remanence:mat low temperatures the structure can only nucleate for small perpendicular anisotropy, i.e., close to the RPT Fe thickness; at higher temperatures nucleation is possible for Fe thicknesses well below the RPT thickness. We also report that the bulk cubic anisotropy term, ${\mathrm{K}}_{1}$, changes sign in the vicinity of the RPT Fe thickness. Consequently, we are able to delineate an Fe thickness-temperature phase diagram which identifies at least one point in (Fe thickness, temperature) space where the RPT coincides with vanishing ${\mathrm{K}}_{1}$. The identification of such a point is a necessary step towards the realization of a two-dimensional Heisenberg magnet.