AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeP

Paper MI-WeP12
Ferromagnetism in Epitaxial Mn:Ge Films

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: A.P. Li, Oak Ridge National Laboratory
Authors: A.P. Li, Oak Ridge National Laboratory
C. Zeng, The University of Tennessee
Z. Gai, Oak Ridge National Laboratory
J.F. Wendelken, Oak Ridge National Laboratory
H.H. Weitering, The University of Tennessee and Oak Ridge National Laboratory
J. Shen, Oak Ridge National Laboratory
Correspondent: Click to Email
We report on the magnetic properties of Mn-doped homo-epitaxial Ge films. Two different approaches are used to fabricate ferromagnetic Ge films. In the first approach, Mn-doped Ge films were grown on (2x1) reconstructed Ge(100) using molecular beam epitaxy (MBE) as was reported by Y.D. Park et al (Science 295, 651 (2002)). The Mn-concentration was varied between 1% and 5%. The Ge films show ferromagnetic ordering with Curie temperatures ranging from 25 K to 295 K, which have been determined from the remnant magnetization measured with a SQUID magnetometer. The magnetic response appears to consist of two different contributions, namely the ferromagnetic response from the dilute magnetic semiconductor (DMS) and the response from ferromagnetic alloy precipitates. X-ray diffraction (XRD), Rutherford Backscattering, and ion-channeling experiments were used to characterize the stoichiometry, homogeneity, and epitaxial quality of the films. In the second approach, a 40 nm Mn film is deposited onto Ge(111) and annealed to 150 °C for several minutes. Scanning Tunneling Microscope and XRD measurements show a high-quality epitaxial Mn@sub 5@Ge@sub 3@ alloy film with Mn@sub 5@Ge@sub 3@(001)//Ge(111). The Curie temperature of this ferromagnetic alloy film is 295 K, which is similar to that of bulk Mn@sub 5@Ge@sub 3@. The identical Tc of the epitaxial alloy film and Mn-doped Ge(100) films strongly suggests that the DMS film contains bulk Mn@sub 5@Ge@sub 3@ precipitates. These precipitates are below the detection limit of XRD. This thin film ferromagnetic system has good potential for spin-injection studies in silicon-compatible semiconductors. This research was sponsored by the LDRD Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.