AVS 51st International Symposium
    Semiconductors Monday Sessions
       Session SC+MI-MoM

Invited Paper SC+MI-MoM6
Induced Host Moments and Mn Electronic Structure in Mn-Doped Iii-V Ferromagnetic Semiconductors

Monday, November 15, 2004, 10:00 am, Room 304B

Session: Dilute Magnetic and Ferromagnetic Semiconductors
Presenter: D.J. Keavney, Argonne National Laboratory
Authors: D.J. Keavney, Argonne National Laboratory
D. Wu, University of Utah
J. Shi, University of Utah
E. Johnston-Halperin, University of California, Santa Barbara
D.D. Awschalom, University of California, Santa Barbara
Y. Cui, University of Wisconsin-Milwaukee
L. Li, University of Wisconsin-Milwaukee
Correspondent: Click to Email
We have used soft x-ray magnetic circular dichroism (XMCD) and absorption spectroscopy (XAS) to examine induced host magnetic moments and the local Mn environment in Mn-doped GaAs and GaN. X-ray absorption probes unoccupied states via transitions from deep core levels, thus providing electronic structure information with element specificity. With circularly polarized radiation at the L edges, element specific moments can be detected via their projection onto the Mn 3d and host 4s states, providing a test of predictions made by the carrier-mediated model of ordering. In (Ga,Mn)As, we find small XMCD signals at the onset of the absorption edge for both Ga and As, which we attribute to induced 4s moments. The relative orientations of all three elements are as expected for carrier-mediated coupling, and we estimate that the As moment is larger than the Ga moment. In (Ga,Mn)N, we detect a weak Ga XMCD signal 2-3 eV above the absorption edge of opposite sign to that in (Ga,Mn)As, which may be attributable to Mn 3d tails at the Ga sites. The absence of a Ga 4s moment would suggest a weaker p-d hybridization consistent with the deeper position of the Mn acceptor level. In both systems, XAS shows that Mn is divalent, although with differing amounts of line broadening, suggesting that the Mn 3d localization varies significantly depending on the host. (Ga,Mn)N has a lineshape closer to atomic Mn 2+ than (Ga,Mn)As. These results show that the Mn 3d and valence band electronic structure in doped III-V systems is strongly dependent on the host, and have implications for the degree of p-d hybridization and the coupling mechanism responsible for ferromagnetism. Use of the Advanced Photon Source was supported by the U.S. DOE, Office of Science, Contract No. W-31-109-Eng-38. Work at the Univ. of Utah was supported by ONR/DARPA grant No. N00014-02-10595, at UCSB by ONR/DARPA grant No. N00014-99-1-1096 and AFOSR F49620-02-10036, and at Univ. of Wisconsin by NSF DMR-0094105.