Determination of the Dielectric Function of Nickel Ferrite Thin Films Luis A. Barrera1, Khadijih N. Mitchell1, Lina S. Abdallah1, Stefan Zollner1, Arunava Gupta2 1Department of Physics, New Mexico State University, Las Cruces, NM, 88003 2Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL, 35487 Background 5 mm x 5 mm substrate 1 micron thick Single side polished NiFe2O4 has a crystal structure of inverse spinel MgAl2O4 has a crystal structure of normal spinel NiFe2O4 is an indirect band gap system Face-centered cubic oxygen lattice Results Conclusions NiFe2O4 exhibits one indirect band gap (minority channel) and two different direct band gaps (minority and majority channels) The increase of Fe leads to cation disorder, thus broadening the lattice vibration The metallic properties are 1000 times weaker than actual metal Characterized the optical properties of nickel ferrite thin films Modeled data using Tauc-Lorentz oscillator Found approximate band gaps Plotted the absorption coefficient This characterization will allow… Stoichiometric Fe-rich 2 srough 64.88 Å 1 genosc 11346.13 Å 0 spinel vuv tabulated (1) 1 mm 2 srough 48.54 Å 1 genosc 11135.72 Å 0 spinel vuv tabulated (1) 1 mm MSE: 2.569 MSE: 3.845 Applications Fiber-optic thermometers Electronics Data Storage Spintronics Objective Precision measurements of the optical constants for NiFe2O4 with MgAl2O4 substrate in stoichiometric and Fe-rich samples using variable-angle spectroscopic ellipsometry. References C. Himcinschi, I. Vrejoiu, G. Salvan, M. Fronk, A. Talkenberger, D. Zahn, D. Rafaja, J. Kortus, J. Appl. Phys. 113, 084101, (2013). A Gupta et al. (need specifics) H. Fujiwara, Spectroscopic Ellipsometry: Principles and Applications (Wiley, Chichester, England, 2007). Method Ellipsometry is a non-invasive optical technique that measures the change in polarization state of a light beam reflected from or transmitted through the sample under study. Some basics: n: index of refraction (real value) k: extinction coefficient (imaginary value) MSE: mean-squared error ε~= ε1+ i ε2 : complex dielectric function n~=n+ik: complex index of refraction ε 1=n2-k2 ε 2=2nk Measurements: 0.76-6.60 eV by 0.02 eV steps slow scan 65-75°with alignment detector Linearly polarized light reflects off the sample surface at an oblique angle, resulting in elliptically polarized light Tauc-Lorentz oscillator models were used to fit the data in the transparent region Atomic Force Microscopy measurements (AFM) were conducted to compare with WVASE32 generated models AFM Image rms: 22.0 Å Image rms: 24.4 Å Acknowledgements We are grateful to Dr. Peter Cooke for guidance on performing atomic force microscopy measurements. This work was supported, in part, by the National Science Foundation under grant numbers DMR-1229558 (MRI), HRD-135011 (New Mexico AMP), and DMR-1104934. NSF HRD # 1305011