Abstract
We report on the mechanism of magnetization reversal in epitaxial Co/Fe bi-layers grown by molecular beam epitaxy on MgO(001) substrates. For Co films thicker than 5 nm, the crystal structure is hexagonal. The Fe layer follows an epitaxial relation relative to the MgO substrate of (001) [100] Fe// (001) [110] MgO. When deposited on a cubic Fe layer, the Co layer follows a bi-crystal epitaxial relation of (11 2- 0) [0001] Co// (001) 〈 100 〉 Fe as previously reported [Popova, Appl. Phys. Lett. 81, 1035 (2002); Wang, J. Appl. Phys. 101, 09D103 (2007)]. The magnetization reversal in-plane follows a cubic fourfold symmetry, which coincides with that of the underlying bcc Fe layer. In this study, we find that the area of each Co crystal domain spans 200-1500 nm2 and that these two domains are approximately evenly distributed. The micromagnetic reversal mechanism is a combination of coherent rotational processes and domain wall displacement. These magnetic domains are sized tens of μm and separated by predominately 90° or occasionally 180° domain walls along the Fe 〈 110 〉 and Fe 〈 100 〉 directions, respectively. The cubic anisotropy of the bi-crystalline Co layer is explained by exchange-coupling between hcp grains with perpendicular crystallographic orientation, each having in-plane uniaxial magnetic anisotropy along its respective [0001] direction.
| Original language | English (US) |
|---|---|
| Article number | 063918 |
| Journal | Journal of Applied Physics |
| Volume | 103 |
| Issue number | 6 |
| DOIs | |
| State | Published - 2008 |
Funding
This research was funded by the Engineering and Physical Sciences Research Council through Grant No. GR/S95800/01, “Epitaxial magnetic nanostructures.” A.K. acknowledges the financial support of the Royal Academy of Engineering and the EPSRC. This manuscript has been created in part by UChicago Argonne, LLC, operator of Argonne National Lab: a US DoE Office of Science lab operated under contract no. DE-AC02-06CH11357. The authors thank Dr. L. J. Singh and Dr. S. Lozano-Perez for their assistance with VSM measurements and multivariate statistical analysis of EELS data, respectively.
ASJC Scopus subject areas
- General Physics and Astronomy