Regensburg 2002 – wissenschaftliches Programm
MA 15.8: Vortrag
Donnerstag, 14. März 2002, 17:00–17:15, H10
Critical phenomena near the surface of antiferromagnetic single crystals and thin films studied by depth selective CEMS — •Sarbari Bhattacharya1, Branko Stahl1,2, Jens Ellrich1, Mohammad Ghafari1, Horst Hahn1, Holger Schmitt1, Marcel Müller1, and Jörg Ebert1 — 1Fachbereich Material- und Geowissenschaften, Petersenstr. 23, TU Darmstadt, 64287 Darmstadt — 2Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe
In an FeBO3 single crystal a wetting phenomenon was oberserved near the Neel temperature. Depth selective conversion electron Möss bauer spectroscopy (DCEMS) gives access to the thickness of this wetting layer as a function of reduced temperature. In addition, the line shape analysis reveals dynamical aspects of the magnetic moments. The observed wetting phenomenon is unexpected for the present second order phase transition. The partial exchange of Fe with Ga in the single crystal changes the behaviour to the expected ordinary surface transition. The Neel temperature of 348 K in the pure crystal is reduced to ≈270 K. DCEMS experiments on two γ-FeOOH thin films of different thickness show a similar magnetic behaviour as in the single crystals. Due to the finite thickness of the thinner film a reduction in the Neel temperature is observed whereas the thicker film clearly exhibits bulk properties.