Exchange bias measurements of epitaxial magnetic oxide exchange bias bilayers.

It has been shown in epitaxial bilayers that antiferromagnetic exchange coupling exists at atomically abrupt interfaces between ferromagnetic oxides La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ and SrRuO$_{3}$[1,2]. We have grown the bilayers on (001) SrTiO$_{3}$ substrates by pulsed laser deposition with atomic layer control. By analyzing the in-plane magnetization loops of the LSMO layer, and the total magnetization of the (frozen) SRO layer, we determine the exchange field of the bilayer and the domain structure of the SrRuO$_{3}$ biasing layer as a function of cooling field. This data shows evidence for domain walls both parallel and perpendicular to the interface. We support this conclusion with a simple energy minimization including contributions from the interfacial exchange, dipole interaction with the cooling field, domain wall energies, and magnetostatic energy. We also pattern the samples with e-beam and x-ray lithography techniques. Size effect on coercivities of both LSMO and SRO electrodes and exchange bias in the bilayers will be discussed. [1] X. Ke, M. S. Rzchowski, L.J. Belenky, C. B. Eom$,$ \textit{Appl. Phys. Lett}, \textbf{84}, 5458 (2004). [2] X. Ke, L.J. Belenky, C. B. Eom, M. S. Rzchowski, \textit{J. Appl. Phys}. \textbf{97}, 10K115 (2005).