Ion Beam Deposited Gmr Materials
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ION BEAM DEPOSITED GMR MATERIALS J. M. Lannon Jr.*, C.C. Pace*, D. Temple*, G.E McGuire*, A.F. Hebard**, and M. Ray*** * MCNC, Materials and Electronic Technologies Division, Research Triangle Park, NC, [email protected] ** Department of Physics, University of Florida, Gainesville, FL *** Integrated Electro-Optics, Inc., Raleigh, NC
ABSTRACT Ion beam sputter deposition (IBSD) techniques for deposition of giant magnetoresistance (GMR) films have been studied using an automated IBSD system designed and built in-house. We have studied the properties of Fe/Cr multilayers deposited using either Ar or Xe ions with the primary ion beam energy varying from 500 eV to 1100 eV. The films were characterized using transmission electron microscopy (TEM), atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), magnetization measurements, and magnetoresistance measurements. The maximum value of GMR obtained was 49% (measured at 10K). For the Cr spacer thickness layer chosen, this GMR ratio is larger than the values reported for polycrystalline Fe/Cr multilayers deposited by magnetron sputtering. In general, we have found that GMR ratios for the Fe/Cr multilayers increase with decreasing primary ion beam energy, and are greater for films deposited using Xe ions than for films deposited using Ar ions. We explain the observed effects on the basis of energy distributions of sputtered atoms and backscattered working gas atoms (neutrals). The energy distributions were calculated using TRIM (Transport of Ions in Matter) software based on the Monte Carlo method. INTRODUCTION Since its discovery in 1988 by Baibich et al.1, the giant magnetoresistant (GMR) phenomenon has led to rapid expansion of the magnetoelectronics field. The GMR effect was originally observed in magnetic multilayered structures deposited by molecular beam epitaxy (MBE). Techniques such as magnetron sputtering, e-beam evaporation, and ion beam sputtering have also been shown effective for deposition of GMR multilayers.2 However, continued advancements in GMR technologies requires better understanding of the influence of deposition conditions on the properties of resulting magnetic multilayer films. We present results from ion beam sputter deposition (IBSD) studies of magnetic thin film multilayers designed to address this issue. EXPERIMENTAL DETAILS Fe/Cr multilayers were deposited at room temperature on 4” Si(100) wafers in an inhouse, automated ion beam sputter deposition system at operating pressures of 2 to 7 x 10-4 Torr F9.12.1
(base pressures of 10-9 to 10-8 Torr). Films were deposited using an rf ion source that could provide either Ar+ or Xe+ sputtering species with primary ion beam energies ranging from 500 to 1100 eV. Deposition rates ranged from 10 to 60 Å/min, depending on the primary ion beam energy. Typical Fe/Cr multilayer structures had the form Si/Cr(50Å)/[Fe(20Å)/Cr(tCr))]n/Cr(50Å-tCr) where tCr is the Cr spacer thickness and n is the number of periods. The Cr spa
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