AVS 52nd International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Paper MI-ThA5
Detailed Investigation of Cr-doped Anatase TiO@sub 2@ as a Potential DMS

Thursday, November 3, 2005, 3:20 pm, Room 204

Session: Magnetic Oxides
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
V. Shutthanandan, Pacific Northwest National Laboratory
C.M. Wang, Pacific Northwest National Laboratory
D.E. McCready, Pacific Northwest National Laboratory
J.E. Jaffe, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
Since the initial discovery of room temperature ferromagnetism in Co-doped anatase TiO@sub 2@ in 2001, there has been an explosion of interest in doped transition metal oxides as potential dilute magnetic semiconductors (DMSs), which may find application in future spintronic devices. The high electron mobility in n-type anatase TiO@sub 2@ (reduced to create oxygen vacancies) makes it an attractive candidate as a oxide semiconductor host material. Doping with Cr instead of Co is advantageous since Cr metal (antiferromagnetic) is more easily oxidized than Co metal (ferromagnetic). In this talk, we present results of a detailed study of Cr-doped anatase TiO@sub 2@ deposited by oxygen-plasma-assisted molecular beam epitaxy. Phase-pure, epitaxial films are obtained with particle-free surfaces and uniform distribution of Cr. Crystalline perfection is controlled by the deposition rate; nearly perfect films can be obtained at a sufficiently slow rate. For faster deposition rates, room temperature ferromagnetism is observed, with ~ 0.5 µ@sub B@/Cr and a Curie temperature of 690 K. Regardless of deposition rate, XANES and EXAFS indicate Cr incorporates into the anatase lattice as Cr(III), requiring one oxygen vacancy for every two dopants to maintain charge neutrality. The specific site occupancy, as well as the complex role of oxygen vacancies and crystalline defects in the ferromagnetic ordering, will be discussed. The electronic properties of Cr-doped anatase have been investigated in detail by XPS, XAS/XES, XMCD, and anomalous Hall measurements, as well as theoretical calculations of the band structure. These results and the implications for spintronic applications of Cr-doped anatase will be presented.