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MA: Fachverband Magnetismus

MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)

MA 19.26: Poster

Dienstag, 15. März 2011, 10:45–13:00, P2

Magnetotransport properties of iron microwires grown by local electron beam induced activation — •Fabrizio Porrati¹, Roland Sachser¹, Marie-Madeleine Walz², Florian Vollnhals², Hans-Peter Steinrück², Hubertus Marbach², and Michael Huth¹ — ¹Physik. Institut, Goethe-Univ., Frankfurt a. M. — ²Physikalische Chemie II, Uni Erlangen-Nürnberg, Erlangen

We have grown iron microwires under UHV conditions and we have measured their magnetic and transport properties in a 4-probe geometry. The growth process takes place in two-steps: First, a SiO₂ substrate is locally activated by electron beam irradiation. Second, the molecules of a precursor gas (Fe(CO)₅) injected in the UHV chamber decomposes and grows autocatalytically. The growth process can be controlled by tuning the electron beam dose, the dosage of precursor flux and the deposition time. For the transport measurements, the temperature dependence of the longitudinal resistivity (ρ_xx) shows a typical metallic behaviour with resistivity at room temperature of about 30 mW cm, i.e. only a factor 3 larger than the bulk value. Furthermore, we have measured isothermal Hall-resistivities in the range between 4.2 K and 260 K. These measurements reveal positive ordinary and anomalous Hall coefficients, which, respectively, decrease and increase by increasing temperature. The relation between anomalous Hall resistivity (ρ_AH) and longitudinal resistivity is quadratic, ρ_AH ∼ ρ_xx², revealing an intrinsic origin of the anomalous Hall effect. Finally, we have measured at low temperature in the transversal geometry a negative magnetoresistance in the order of 0.2%.