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MA: Fachverband Magnetismus
MA 44: Surface Magnetism (Joint Session with O) - Adatoms on surfaces
MA 44.9: Vortrag
Donnerstag, 19. März 2015, 17:15–17:30, H 0110
Uncompensated antiferromagnets for artificial magnetic semiconductors — •Michalis Charilaou1,2,3, Simca Bouma2,3, Catherine Bordel2,3, and Frances Hellman2,3 — 1Department of Materials, ETH Zurich, Zurich, Switzerland — 2Department of Physics, University of California Berkeley, Berkeley, California, USA — 3Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
Like ferromagnets (FM), antiferromagnets (AFM) exhibit spontaneous long-range spin ordering below a transition temperature. The net magnetization of a perfect AFM is zero, however; defects such as vacancies, grain boundaries, or surfaces can create an uncompensated net magnetization. As a specific example we consider AFM CoO, which consists of AFM-coupled FM (111) planes; (111)-oriented epitaxial films with an odd number of planes will exhibit a non-zero net magnetization due to uncompensated surfaces. These uncompensated surfaces have been used to produce an artificially-structured FM semiconductor using epitaxial layers of AFM CoO with a doped semiconductor Al:ZnO (AZO). Both M(T) and the anomalous Hall effect show oscillatory behavior with thickness of either CoO (compensated vs uncompensated) or AZO (RKKY-type oscillations related to the AZO Fermi wavevector due to electron-induced coupling between Co moments at its two CoO surfaces). The experimental results are complemented by theoretical calculations, which show that the thermodynamic behavior of the magnetization in uncompensated AFM is highly versatile, and is dominated by the exchange coupling on the surface.