Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 32: Magnetic Thin Films I
MA 32.8: Vortrag
Mittwoch, 16. März 2011, 12:45–13:00, HSZ 04
Magnetic Properties of (CoFe)x(MgO)100−x nanogranular thin films investigated by FMR spectroscopic tool — •Olga Meshcheriakova1, Yuri Kudryavtsev2, Volodymyr Yermolenko2, Benjamin Balke1, Gerhard Fecher1, and Claudia Felser1 — 1Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg-University Mainz, D-55099 Mainz, Germany — 2Institute of Metal Physics, National Academy of Sciences of Ukraine, 252680 Kiev-142, Ukraine
The ferromagnetic and magneto-transport properties of
(CoFe)x(MgO)100−x nanogranular films were investigated. Tunneling magnetoresistance (TMR) of magnetic nanogranular films has been measured by four-probe DC conductivity measurements depending on the concentration of (CoFe)x ferromagnetic granules and the thermal treatment. The maximum TMR effect of 1.5% at H=6500 Oe occurs at x=50 in the as-deposited films. Annealing process leads to drastic reduction of TMR due to the ferromagnetic granules coalescent into magnetic clusters, thus the conductance changes from tunneling to metal type. FMR spectra are experimentally obtained for the samples in the initial and annealed states in a range of concentrations x=90, 73, 60, 50, 35, and 23. The annealing of (CoFe)x(MgO)100−x nanogranular films at 350∘C during 1 hour causes significant changes of magnetic properties of the films: effective and saturation magnetizations significantly increase and initially paramagnetic films become ferromagnetic due to the slight size increasing of ferromagnetic clusters. Further research requires more detailed structural analysis.