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Epitaxial Zn<sub>x</sub>Fe<sub>3−x</sub>O<sub>4</sub> thin films : A spintronic material with tunable electrical and magnetic properties

Epitaxial ZnxFe3−xO4 thin films : A spintronic material with tunable electrical and magnetic properties

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VENKATESHVARAN, Deepak, Matthias ALTHAMMER, Andrea NIELSEN, Stephan GEPRÄGS, M. S. RAMACHANDRA RAO, Sebastian T. B. GÖNNENWEIN, Matthias OPEL, Rudolf GROSS, 2009. Epitaxial ZnxFe3−xO4 thin films : A spintronic material with tunable electrical and magnetic properties. In: Physical Review B. American Physical Society (APS). 79(13), 134405. ISSN 2469-9950. eISSN 2469-9969. Available under: doi: 10.1103/PhysRevB.79.134405

@article{Venkateshvaran2009Epita-53287, title={Epitaxial ZnxFe3−xO4 thin films : A spintronic material with tunable electrical and magnetic properties}, year={2009}, doi={10.1103/PhysRevB.79.134405}, number={13}, volume={79}, issn={2469-9950}, journal={Physical Review B}, author={Venkateshvaran, Deepak and Althammer, Matthias and Nielsen, Andrea and Geprägs, Stephan and Ramachandra Rao, M. S. and Gönnenwein, Sebastian T. B. and Opel, Matthias and Gross, Rudolf}, note={Article Number: 134405} }

Opel, Matthias terms-of-use Venkateshvaran, Deepak Gross, Rudolf Gross, Rudolf Nielsen, Andrea eng Nielsen, Andrea 2021-03-29T10:42:25Z Althammer, Matthias Ramachandra Rao, M. S. Epitaxial Zn<sub>x</sub>Fe<sub>3−x</sub>O<sub>4</sub> thin films : A spintronic material with tunable electrical and magnetic properties Venkateshvaran, Deepak Ramachandra Rao, M. S. 2009 Opel, Matthias Gönnenwein, Sebastian T. B. Geprägs, Stephan Geprägs, Stephan 2021-03-29T10:42:25Z Althammer, Matthias The ferrimagnetic spinel oxide Zn<sub>x</sub>Fe<sub>3−x</sub>O<sub>4</sub> combines high Curie temperature and spin polarization with tunable electrical and magnetic properties, making it a promising functional material for spintronic devices. We have grown epitaxial Zn<sub>x</sub>Fe<sub>3−x</sub>O<sub>4</sub> thin films (0≤x≤0.9) on MgO(001) substrates with excellent structural properties both in pure Ar atmosphere and an Ar/O2 mixture by laser molecular beam epitaxy and systematically studied their structural, magnetotransport, and magnetic properties. We find that the electrical conductivity and the saturation magnetization can be tuned over a wide range (10<sup>2</sup>…10<sup>4</sup> Ω<sup>−1</sup> m<sup>−1</sup> and 1.0…3.2 μ<sub>B</sub>/f.u. at room temperature) by Zn substitution and/or finite oxygen partial pressure during growth. Our extensive characterization of the films provides a clear picture of the underlying physics of the spinel ferrimagnet Zn<sub>x</sub>Fe<sub>3−x</sub>O<sub>4</sub> with antiparallel Fe moments on the A and B sublattices: (i) Zn substitution removes both Fe<sup>3+</sup><sub>A</sub> moments from the A sublattice and itinerant charge carriers from the B sublattice; (ii) growth in finite oxygen partial pressure generates Fe vacancies on the B sublattice also removing itinerant charge carriers; and (iii) application of both Zn substitution and excess oxygen results in a compensation effect as Zn substitution partially removes the Fe vacancies. Both electrical conduction and magnetism are determined by the density and hopping amplitude of the itinerant charge carriers on the B sublattice, providing electrical conduction and ferromagnetic double exchange between the mixed-valent Fe<sup>2+</sup><sub>B</sub>/Fe<sup>3+</sup><sub>B</sub> ions on the B sublattice. A decrease (increase) in charge carrier density results in a weakening (strengthening) of double exchange and thereby a decrease (increase) in the conductivity and the saturation magnetization. This scenario is confirmed by the observation that the saturation magnetization scales with the longitudinal conductivity. The combination of tailored Zn<sub>x</sub>Fe<sub>3−x</sub>O4 films with semiconductor materials such as ZnO in multifunctional heterostructures seems to be particularly appealing. Gönnenwein, Sebastian T. B.

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