Regensburg 2000 – wissenschaftliches Programm
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AM: Magnetismus
AM 19: Spektroskopie I
AM 19.8: Vortrag
Donnerstag, 30. März 2000, 11:30–11:45, H22
ARUPS study of Mn-Bi surface alloys — •A. Borgschulte, D. Menzel, M. Broschwitz, M. Rode, U. Barkow, and J. Schoenes — TU Braunschweig, Institut für Halbleiterphysik und Optik
Thin films of Mn-Bi alloys have been prepared in-situ by controlled annealing of Mn overlayers on epitaxial Bi (0001) films on BaF2 (111). Mn and Bi evaporation was performed in an UHV chamber using Knudsen cells with the substrates hold at room temperature. Afterwards the films have been annealed at different temperatures. AES, RHEED and UPS studies have shown that two apparently different ordered alloys can be formed in this way. For an Mn coverage smaller than 25 Å the system builds a Bi phase, in which the Mn is dissolved without changing the crystal structure of the pure Bi (0001) film. The surface of this alloy orders in a (2 × 3) reconstruction. For a larger amount of Mn, clusters of the intermetallic compound MnBi are formed. We show the dependence of the work function of the alloys on the Mn coverage measured with UPS using a He discharge lamp. The work function reaches a sharp maximum at 25 Å Mn, which can be explained by the above described structural transition. Angle-resolved photoelectron spectroscopy has been performed at the TGM3 beamline of BESSY I, using a movable hemisperical electron-analyser (ARIES). We have measured the band structure in the Γ − A direction of the MnBi films at different temperatures to investigate the electronic structure during the annealing process. We found a strong temperature dependence of the bandwidth of the Mn states and of the density of states at the Fermi energy.