Regensburg 2004 – scientific programme
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MA: Magnetismus
MA 4: Oberfl
ächenmagnetismus
MA 4.6: Talk
Monday, March 8, 2004, 11:30–11:45, H22
Spin waves in ultrathin Fe films on Co/Cu(001) — •Markus Etzkorn1, P. S. Anil Kumar1, W. Tang1, R. Vollmer1, H. Ibach2, and J. Kirschner1 — 1Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle — 2Institut für Schichten und Grenzflächen ISG3, Forschungszentrum Jülich, 52425 Jülich
By using spin polarized electron energy loss spectroscopy (SPEELS) we measured spin-wave excitations in 3 ML Fe on 1 ML Co/Cu(001). Similar to Co on Cu(001) [1], the spin waves appear as a single peak in the SPEEL-spectra that can be followed up to the surface Brillouin zone (SBZ) boundary. The spin-wave energy at the SBZ boundary is about 140 meV. The ratio of spin-wave width to spin-wave energy is about one for large wave vector spin waves. This suggests that these spin waves strongly interact with Stoner excitations. In contrast to the case of Co the dispersion in Fe can not be fitted by a nearest neighbor (NN) Heisenberg model with a single exchange coupling constant J. In theoretical calculations [2] the exchange coupling constant of the surface layer of Fe on Cu(001) is enhanced by about a factor of 2 compared to its bulk value. Using a NN Heisenberg model with an enhanced surface exchange coupling constant J1 = 2J a spin-wave stiffness of about 150 meVÅ2 results from the fit to the data. This is significantly lower than the value of bulk bcc Fe (280 meVÅ2).
[1] R. Vollmer, M. Etzkorn, P. S. Anil Kumar, H. Ibach, and J. Kirschner, Phys. Rev. Lett. 91 (2003) 147201.
[2] M. Pajda, J. Kudrnovský, I. Turek, V. Drchal, and P. Bruno, Phys. Rev. Lett. 85 (2000) 5424.