Symmetry breaking effects in epitaxial magnetic thin films: Nonsymmetric reversal and butterfly remanence behavior
David Ecija, Erika Jim\'{e}nez, Nikolai Mikuszeit, Nicol\ ' { a} s Sacrist\{'a}n, Julio Camarero, Jose Mar\ ' { \ i} a Gallego, Jan Vogel, and Rodolfo Miranda

A consistent picture which explains the effects of magnetic anisotropy symmetry breaking on the magnetic properties of epitaxial magnetic thin films is provided, including experimental results in $\gamma$'-Fe$_{\rm 4}$N(100) thin films and numerical simulations. As expected for a thin film with four-fold crystal symmetry, the results show the existence of two easy and two hard magnetization axes. But, in this case, the easy axes are \emph{not orthogonal}, the hard axes are \emph{not equivalent}, the magnetization reversal behavior around the two easy axes is \emph{not symmetric}, and the reversal behaviors of the two hard axes are \emph{not alike}. As a consequence, the polar plot of the remanence displays a \emph{butterfly} shape behavior. These effects depend on additional terms of the magnetic anisotropy. Our results are extended to other symmetry breaking epitaxial magnetic systems.

© 2008 The American Physical Society.