AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThM

Paper MI-ThM9
MBE Growth and Room Temperature Ferromagnetism in Epitaxial Co-doped SrTiO@sub 3@

Thursday, November 18, 2004, 11:00 am, Room 304A

Session: Magnetic Oxides and Half-Metallics
Presenter: T.C. Kaspar, Pacific Northwest National Laboratory
Authors: T.C. Kaspar, Pacific Northwest National Laboratory
T.C. Droubay, Pacific Northwest National Laboratory
S.M. Heald, Pacific Northwest National Laboratory
C.M. Wang, Pacific Northwest National Laboratory
V. Shutthanandan, Pacific Northwest National Laboratory
S.T. Thevuthasan, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
Room temperature ferromagnetism in dilute magnetic semiconductors (DMSs) is highly desirable for practical spintronic devices. The observation of room temperature ferromagnetic behavior in doped wide bandgap semiconducting oxides such as Co-doped ZnO, Mn-doped ZnO, and Co-doped anatase and rutile TiO@sub 2@ has raised the possibility of DMS behavior in other oxide systems. Work on these materials has also revealed the critical importance of thorough materials characterization to rule out ferromagnetic contributions from metallic clusters or other secondary phases. Recently, Co-doped La@sub 0.5@Sr@sub 0.5@TiO@sub 3@ was found to exhibit ferromagnetic behavior at room temperature.@footnote 1@ In the present study, epitaxial SrTi@sub 1-x@Co@sub x@O@sub 3@ thin films (0 < x < 0.15) have been deposited on SrTiO@sub 3@(001) substrates by oxygen-plasma-assisted molecular beam epitaxy (OPAMBE). Smooth films free of surface particles or clusters are obtained. As-deposited films are insulating (@rho@ > 5 k@Omega@-cm); however, room temperature ferromagnetism is observed for < 5% Co doping, with a high magnetic moment and 10-25% remanence. Films doped at higher concentrations (> 5%) do not exhibit ferromagnetism. Thorough materials characterization was employed, including XPS for film composition, AFM and TEM to observe film morphology and the possible inclusion of secondary phases, and RBS and PIXE to determine the precise Co concentrations. A comprehensive study of Co K-edge XANES and EXAFS data to determine details of the Co charge state and local environment was also carried out. F-center mediated exchange will be discussed as the possible mechanism of ferromagnetic ordering in Co:STO. In addition, preliminary results of epitaxial SrTi@sub 1-x@Co@sub x@O@sub 3@ growth on Si(001) will be presented, and the differences in deposition on oxide and semiconductor substrates will be discussed. @FootnoteText@ @footnote 1@ Zhao, Y.G., et al. Appl. Phys. Lett. 83, 2201 (2003).