[Zurück]

P. Varga, W. Rupp, B. Kamenik, M. Schmid:
"Ion beam induced magnetism of thin Fe films on Cu(100)";
Poster: 24th Europ. Conf. on Surface Science (ECOSS-24), Paris/F; 06.09.2006; in: "European Conference on Surface Science", (2006), S. 230.

The structure and magnetism of ultra thin epitaxial Fe films grown on Cu(100) at 300 K (RT) have been investigated by STM (scanning tunnelling microscopy), low-energy electron diffraction (LEED) and by surface magneto-optical Kerr effect (SMOKE) [1]. Hysteresis loops in longitudinal and polar geometry can be determined. Depending on the film thickness, three regimes with different magnetic properties and different orientation of the magnetic anisotropy are known [2] and could be confirmed. Further it is also known that the fcc phase, which has no magnetic moment, can be achieved at room temperature (RT) only for a thickness of 5 to 10 monolayers (ML). In these films small (needle-like) nuclei of the bcc structure were found [3]. We have observed that in these Fe films the phase transition from the fcc phase to the bcc phase can be induced and promoted by ion bombardment. By LEED measurements we observe the structural change from fcc to bcc-like structures after ion bombardment (e.g. ion dose around 0,5 Argon ions / surface atom). At RT, the structural transition is accompanied by a change of in-plane magnetization from paramagnetic to ferromagnetic behaviour. Additionally, our SMOKE data show the disappearance of the low temperature surface ferromagnetism (with perpendicular magnetic anisotropy) [2, 4] as the films becomes bcc during ion bombardment.
The magnetic properties and crystallographic structure of such treated films depending on ion dose, ion energy and ion mass will be discussed.


[1] S.D. Bader, J. Magn. Magn. Mater. 100, 440-454 (1991)
[2] J. Thomassen, F. May, B. Feldmann, M. Wuttig and H. Ibach, Phys. Rev. Lett. 69, 3831 (1992)
[3] A. Biedermann, M. Schmid and P. Varga, Phys. Rev. Lett. 86, 464 (2001)
[4] A. Biedermann, R. Tscheließnig, Ch. Klein, M. Schmid and P. Varga, Surf. Sci. 563, 110-126 (2004)

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