Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 44: Magnetic Half-metals and Oxides I
MA 44.3: Vortrag
Mittwoch, 16. März 2011, 17:30–17:45, HSZ 401
Cation energetics in epitaxially strained inverse spinel ferrites CoFe2O4 and NiFe2O4 — •Daniel Fritsch and Claude Ederer — School of Physics, Trinity College Dublin, Ireland
Inverse spinel ferrites CoFe2O4 (CFO) and NiFe2O4 (NFO) are both insulating ferrimagnetic oxide materials with high magnetic ordering temperature and large saturation magnetisation which make them very attractive for a variety of applications. Many of these applications require the corresponding materials to be grown on lattice-mismatched substrates which can incorporate significant amounts of strain in the thin films. It has been shown that density functional theory (DFT) calculations together with the Hubbard “+U” approach provide reliable insight in strain-induced changes of the structural and magnetic properties of these materials [1].
The degree of inversion λ in spinel materials describes the concentration of divalent cations (Co2+, Ni2+) on the octahedrally coordinated B-sites. While for bulk NFO the inversion is essentially complete, i.e., λ = 1, for CFO the degree of inversion can depend strongly on the specific preparation conditions and is typically around 0.7 .. 0.8. We present DFT total energy calculations for CFO and NFO with different degrees of inversion and different amounts of epitaxial strain. We address the question of whether epitaxial strain can influence the degree of cation inversion in these materials, and compare our results with available experimental data.
[1] D. Fritsch and C. Ederer, Phys. Rev. B 82, 104117 (2010).