Optical Properties of thin Fims of oxidized Ni-Fe.
Poster Presentation at the 2013-WISE conference.
Texas State University at San Marcos, Department of Physics, RFM 3228, 601 University Drive, San Marcos, TX78666.
Nickel Iron, commonly referred to as permalloy, is a magnetic material that is used in the reading heads of magnetic hard disks. Goran et al recently showed that the performance of reading heads employing permalloy can be significantly enhanced up to a factor of 10 if the permalloy layer is partially oxidized. In order to apply oxidized permalloy (PyO) in the production line of hard disk reading heads, one would need a technique to monitor the thickness of a thin PyO layer. Film thicknesses of transparent layers are normally measured by optical spectroscopy. One would measure the reflection spectrum and determine the film thickness from the observed interference maxima and minima in the spectra and the optical properties of the thin film material. The optical properties of PyO, however, have yet to be determined. Therefore PyO cannot be used in electronic devices at this moment.
Measurements were made on samples made by reactive dual ion beam sputtering on glass substrates. The samples were deposited at room temperature on cleaned glass microscope slides mounted to a water cooled substrate. Samples were rotated during deposition in order to ensure an uniform film. The optical properties of the substrates and the samples were measured using a Woollam M2000 variable angle spectroscopic ellipsometer. The transmission spectra shows that PyO is transparent above 600 nm and strongly absorbs below 300 nm indicating a band gap between 2 and 4 eV. The optical properties above 600 nm are well described by a Cauchy dispersion and can be used to determine the film thickness. Optical properties over the measured spectral range (200nm – 1000 nm) are well described by a Gaussian, a Cody-Lorentz, or a Tauc-Lorentz dispersion. The bandgap obtained from the models varied for different samples and had no physical meaning which suggest that a simple thin film model is not correct.
 Goran Mihajlovic et al., Appl. Phys. Lett. 97, pp. 112502 (2010).
Publications and Presentations:
 Michael Robinson, Maclyn Compton, Wilhelmus Geerts, "Optical Properties of thin films of oxidized NiFe", poster presentation at the 2013 Wise conference, Texas State University, San Marcos.
Michael is currently enrolled in the undergraduate Electrical Engineering program at Texas State University.