Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 28: Magnetic Thin Films III
MA 28.1: Vortrag
Donnerstag, 28. Februar 2008, 14:30–14:45, H 1012
Structural and magnetic properties Nickel/rubrene(peroxide) bilayers — •Wen Li1, Felix Springer2, Manfred Albrecht1, Dietrich R.T. Zahn1, and Georgeta Salvan1 — 1Chemnitz University of Technology, D-09107 Chemnitz, Germany — 2University of Konstanz, Department of Physics,D-78457 Konstanz,Germany
Bilayers of nickel/rubrene were obtained by sequential deposition of rubrene and Ni onto Si(111) substrate under ultra-high vacuum conditions. Ex situ AFM studies show that the growth mode of Ni is significantly influenced by the thickness of the underlying rubrene layer. When deposited onto a 14nm rubrene layer Ni forms large islands, hundreds of nanometers in lateral dimension, with large voids between them. On thicker rubrene layers the Ni islands are much smaller forming an almost continuous film.
The hysteresis curves recorded ex situ by magneto-optical Kerr effect (MOKE) measurements in polar geometry show that the magnetic properties change according to the different growth modes. The hysteresis behavior of Ni(7nm)/rubrene peroxide(14nm) shows a combination of ferromagnetic and superparamagnetic behaviour. When the thickness of the rubrene underlayer increases the system behaves ferromagnetically.
The spectroscopic MOKE measurements show that the signal intensity and the energetic position of the spectral features are strongly influenced by the rubrene thickness. Compared to the single Ni(7nm) layer deposited on Si, the MOKE signal of bilayers can be enhanced by about a factor of three.