Berlin 2012 – wissenschaftliches Programm
MA 27.9: Vortrag
Mittwoch, 28. März 2012, 11:45–12:00, EB 202
Zinc ferrite - magnetic thin films with highly tunable conductivity — •Kerstin Brachwitz, Katja Mexner, Michael Lorenz, Francis Bern, Michael Ziese, Pablo Esquinazi, and Marius Grundmann — Institut für Experimentelle Physik II, Universität Leipzig, Germany
Zinc ferrite (ZnFe2O4) has been investigated in several studies, especially because of its promising magnetic properties. However, also the electrical properties are remarkable and important for the application of ZnFe2O4 in spin filters and magnetic tunnel junctions. In this regard, ZnFe2O4 thin films were grown by pulsed-laser deposition. The substrate temperature TS and the oxygen partial pressure p(O2) were varied for different samples in the range of 430∘C≤ TS ≤ 730∘C and 5· 10−5≤ p(O2)≤ 10−2 mbar, respectively.
The electrical conductivity of the resulting ZnFe2O4 films can be tuned over 7 orders of magnitude in a range from 10−5 to 102 S/m by
varying TS . The conductivity of such thin films is thermally activated with activation energies between 70 and 120 meV. The free carrier concentration and their mobility were determined by anomalous Hall effect measurements. Thin films with the largest conductivity exhibit values of about n=1020 cm−3 and µ=0.07 cm2/Vs.
Furthermore, the structural properties were investigated by X-ray diffraction. These measurements revealed an increasing a-lattice constant with increasing conductivity, indicating a disorder- and vacancy-induced conduction mechanism.
 M. Lorenz et al., Phys. Status Solidi RRL 5, 438 (2011)