Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)

MA 13.3: Poster

Tuesday, March 9, 2004, 15:00–19:00, Bereich A

Influence of thickness on microstructural and magnetic properties in Fe₃O₄ thin films produced by PLD — •A. Bollero, M. Ziese, R. Höhne, H. C. Semmelhack, U. Köhler, A. Setzer, and P. Esquinazi — Division of Superconductivity and Magnetism, University of Leipzig, Linnéstrasse 5, 04103 Leipzig

Films of magnetite (Fe₃O₄) have been prepared on (100) MgAl₂O₄ substrates by pulsed laser deposition (PLD) with a thickness ranging from 10–350 nm. Epitaxial growth of the films has been verified by in-situ RHEED measurements. The relaxation degree of the films and the micro-strains between the grains have been studied by X-ray diffraction. Scanning tunnelling microscopy has revealed a homogeneous microstructure for very thin films, a columnar disposition of elongated grains for films with thicknesses of 80 and 160 nm and the formation of islands for the 350 nm thick film, as those typically observed in bulk magnetite. The Verwey transition at T_V has been investigated via SQUID magnetometry; magnetisation has been measured as a function of the applied field at 300 and 5 K for each sample. Additionally, hysteresis loops have been measured at selected temperatures from 300 to 5 K for two films with thicknesses of 30 and 350 nm. At the isotropic point, T_i ∼ 130 K, coercivity goes through a minimum and then rises cooling below T_V. Higher coercivities are obtained for the thinner film attributed to the strong interfacial strain induced in the film by the lattice mismatch with the substrate.