AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI+SC-FrM

Paper MI+SC-FrM2
Epitaxial Ferromagnet on Ge(111)

Friday, November 7, 2003, 8:40 am, Room 316

Session: Semiconductor Spin Injection
Presenter: C. Zeng, The University of Tennessee
Authors: C. Zeng, The University of Tennessee
J.R. Thompson, The University of Tennessee and Oak Ridge National Laboratory
L.C. Feldman, Vanderbilt University and Oak Ridge National Laboratory
S.C. Erwin, Naval Research Laboratory
H.H. Weitering, The University of Tennessee and Oak Ridge National Laboratory
Correspondent: Click to Email
The difficulty of injecting spin-polarized electrons into a semiconductor is a major bottleneck in spintronics research. There are two ways to realize spin injection. One of these is to fabricate a ferromagnetic- metal/semiconductor heterostructure; the other is to use a dilute magnetic semiconductor (DMS) as the spin aligner. The former method does not work well, mainly because of the large conductivity mismatch between the ferromagnetic metal and semiconductor. The latter method is limited by the low Curie temperature, T@sub c@ of DMS. We have developed a novel interface with good potential for spin injection, namely an epitaxial ferromagnetic Mn@sub 5@Ge@sub 3@ film on Ge(111). The Mn@sub 5@Ge@sub 3@ films are fabricated by depositing Mn and subsequent annealing, or by codeposition of Mn and Ge. Mn@sub 5@Ge@sub 3@(001)//Ge(111) epitaxy relationship is verified by X-ray diffraction results, due to the small lattice mismatch. STM images display (@sr@3x@sr@3)R30° honeycomb structure, which perfectly agrees with the theoretical image of the Mn terminated Mn@sub 5@Ge@sub 3@ (001) surface. RBS and ion-channeling experiments confirmed the stoichiometry and epitaxy of the film. Magnetic measurements reveal a T@sub c@ of about 295 K. The easy axis is in-plane which is most likely due to the shape anisotropy. The multiplet splitting of the Mn 3s core level in XPS indicates an average magnetic moment of 2.6 µ@sub B@ per Mn atom, which is in almost perfect agreement with the spin-resolved band structure calculations and SQUID measurements. This research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.