IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuP

Paper MI-TuP13
Magnetic Coupling in Epitaxial Fe/MgO/Fe Arrays of Micro Tunnel Junctions

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Emerging Materials & Nanostructures Poster Session
Presenter: J.L. Costa-Kramer, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
Authors: J.L. Costa-Kramer, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
J.V. Anguita, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
J.I. Martin, Universidad de Oviedo, Asturias, Spain
C. Martinez-Boubeta, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
A. Cebollada, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
F. Briones, Instituto de Microelectronica de Madrid, CNM, CSIC, Spain
Correspondent: Click to Email
The magnetic properties of planar 100 Fe/ x MgO / 100 Fe epitaxial ferromagnetic micro tunnel junction arrays have been measured for different lateral sizes of the junctions (1-50 µm) and barrier thicknesses; (x=10,20,50,70 ). When the top and bottom electrodes magnetizations are uncoupled, they orient antiparallel in zero field due to the magnetostatic energy gain. On the other hand, the two electrodes magnetizations orient parallel when direct exchange couples them effectively through the barrier, most probably due to a critical density of pinholes. We find that both, lateral size and barrier thickness influence the ratio of junctions with their electrodes magnetization antiparallel to those in which they orient parallel. For a given barrier thickness, there is a threshold below which mostly all of the junction electrodes couple antiparallel. This happens at about 4 µm lateral size for electrodes separated by a barrier of 10 MgO (close to only two MgO unit cells). The field ranges where these phenomena occur agree reasonably well with the predictions from a simple analytical model, in which we solve the energetic balance between magnetostatic energy gain and orientational energy loss for our Fe/MgO/Fe sandwich geometry. In addition, and comparing with our previous results with single layer Fe microtile arrays, we confirm the intuitive picture that the micro sandwich structures can be placed closer than the single layer structures before they interact magnetically with their closest neighbors. This is due to a preferred closure of the magnetic flux between top and bottom electrodes in the sandwich structure, reducing considerably the magnetic field at the closest neighbors positions.