[Zurück]

B. Kamenik:
"Magnetic phase transformation by ion bombardment of Fe films on Cu(100)";
Vortrag: 56. Jahrestagung der Österr. Physikalischen Gesellschaft (ÖPG), TU Graz; 20.09.2006; in: "Tagungsprogramm 56. Jahrestagung der Österreichischen Physikalischen Gesellschaft", (2006), S. 96.

Structure and magnetism of ultrathin epitaxially grown Fe films on Cu(100) at room temperature (RT) have been investigated by STM (scanning tunnelling microscopy), low-energy electron diffraction (LEED) and surface magneto-optical Kerr effect (SMOKE). Hysteresis loops in longitudinal and polar geometry were measured and quantified. Depending on film thickness, three regimes [1] with different magnetic properties and orientation could be confirmed. It is known that the fcc phase, which has no magnetic moment, can be achieved at RT only for a thickness range of 5 to 10 monolayers (ML). In these films small needle-like nuclei of the ferromagnetic bcc structure were found [2]. We observed that the phase transition from the fcc phase to the bcc phase can be induced and promoted by ion bombardment. LEED measurements confirm the structural change from fcc to bcc-like structures during ion bombardment. The structural transition at RT is accompanied by a change of in-plane magnetization from paramagnetic to ferromagnetic behaviour. SMOKE measurements also show a disappearance of the low temperature surface ferromagnetism (of perpendicular magnetic anisotropy) [1, 3] as the film becomes bcc during ion bombardment.
The magnetic properties and crystallographic structure of such films depending on ion dose, ion energy and ion mass will be discussed.

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

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