Electrical and Optical Properties of Permalloy Oxide grown by dual ion beam sputtering.
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Electrical and Optical Properties of Permalloy Oxide grown by dual ion beam sputtering. Maclyn Stuart Compton (1), Nelson A. Simpson (1), Elizabeth G. LeBlanc (1), Michael A. Robinson (2), Wilhelmus J. Geerts (1). (1) Department of Physics, Texas State University, San Marcos. (2) Department of Electrical Engineering, Texas State University, San Marcos. ABSTRACT Electrical and Optical measurements were carried out on permalloy oxide (PyO) thin films made by reactive dual ion beam sputtering at room temperature. VSM measurements at room temperature and 15 Kelvin did not reveal any magnetic moment in 120 nm thick films. The optical refraction and extinction spectra from 200-1000 nm were determined from ellipsometry measurements using a Cody-Lorentz model and provided in a reproducible method to determine the film thickness of PyO films on different substrate materials. PyO is transparent above 700 nm and is strongly absorbing below 500 nm. The resistivity values of PyO samples sputtered at room temperature depend on the oxygen flow rate and is approximately 4E3 Ohm cm for films prepared at 10 sccm. The resistivity of PyO decreases as a function of temperature. The dielectric constant is strongly frequency dependent, decreasing from 500 at 500 Hz to 10 at 1 MHz. INTRODUCTION Permalloy (Py) is used in most magnetic recording heads. It can flip its state easily; and, its magnetic properties do not depend on stress, a quantity that is difficult to control in integrated magnetic thin film heads. Whenever Py is oxidized, its magnetic properties change drastically. This was always seen as a defect in industry where companies would encapsulate Py-based sensors to prevent oxidation. It was recently shown that a lateral spin valve, a sensor used in a magnetic reading head, became much more sensitive whenever the Py layer was oxidized [1]. More recently in 2013, low turn on voltages for hematite water splitting cells were achieved by adding an amorphous NiFeOx layer [2]. So now Permalloy Oxide (PyO) is suddenly a very interesting material to study for devices. But since PyO was always seen as a defect, there is little information published on just PyO. To understand how PyO can be used in devices to make them more efficient we need to understand the electronic properties of PyO itself. And, to be able to apply PyO thin films in devices, we need measurement tools and methods to characterize the PyO, such as the thickness of a PyO layer. Film thicknesses are best measured by optical techniques, but one would need the optical properties of PyO to do so. We therefore also determined its optical properties. EXPERIMENTAL PROCEDURE Dual Ion Beam Sputtering (DIBS) is known to create highly adhesive films with a large density. Since the plasma is contained in the ion guns one can sputter at much lower pressures while not exposing the film directly to the plasma. This leads to dense films that have a superior adhesion to the substrate. Other advantages of DIBS are a better use of gasses and less contamination. The
PyO thin films reported
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