Ferromagnetism and n-type conductivity in Zn$_{1-x}$Fe$_{x}$O

Room temperature ferromagnetism in Zn$_{1-x}$Fe$_{x}$O can be obtained by precipitation of ZnFe$_{2}$O$_{4}$ impurity phase (with the Curie temperature of 440 K) after low-oxygen-pressure synthesis.* This impurity can be controlled by changing the synthesis temperature, which makes this material promising for spintronic applications. We have studied this material by magnetic, transport and thermoelectric experiments. The electrical resistivity shows a semiconducting behavior with $\rho \sim $0.4 $\Omega $cm at 300 K, much lower than Mn- and Co-substituted ZnO. Hall effect measurements show n-type conductivity with mobility $\sim $1-10 cm$^{2}$/Vs. The n-type conductivity is independent of the presence of ferromagnetic impurities. A high negative Seebeck (-300 $\mu $V/K at 300 K) would make this material suitable for thermoelectric applications if its resistivity could be further reduced. *S. Kolesnik et al., J. Appl. Phys. \textbf{95}, 2582 (2004). Supported by NSF (DMR-0302617) and the U.S. Department of Education.