Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 24: Magnetic Heuslers, Half-Metals and Oxides II (organized by MA)
TT 24.4: Vortrag
Montag, 31. März 2014, 16:15–16:30, BEY 118
Combined theoretical and optical band gap determination of NiFe2O4 and CoFe2O4 — •Markus Meinert and Günter Reiss — Center for Spinelectronic Materials and Devices, Bielefeld University, Germany
In a theoretical study we investigate the electronic structure and the band gap of the inverse spinel ferrites NiFe2O4 (NFO) and CoFe2O4 (CFO). The experimental optical absorption spectrum of NFO is well reproduced by fitting the Tran-Blaha parameter in the modified Becke-Johnson (mBJLDA) potential. For CFO, the agreement is less satisfying. The accuracy of the commonly applied Tauc plot to find the optical gap is assessed based on the computed spectra and we find that this approach can lead to a misinterpretation of the experimental data.
The minimum gap of NiFe2O4 is found to be a 1.53 eV wide indirect gap, which is located in the minority spin channel. In CoFe2O4, the band gap is about 0.9 eV wide and is also located in the minority spin channel.