Magnetic and Magneto-Optic Properties of dc Magnetron Sputtered Co-Cr/Al Multilayers
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MAGNETIC AND MAGNETO-OPTIC PROPERTIES OF dc MAGNETRON SPUTTERED Co-Cr/Al MULTILAYERS
G.W. Auner, R. Naik*, U.M. Rao*, Y. Zhao, and B. Wang Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202; *Department of Physics, Wayne State University, Detroit, MI 48202 ABSTRACT
Single layers of Co82Cr18 with thickness in the range of 100-1500A and multilayers of Co-Cr/Al with Co-Cr thickness in the range of 100-200A and Al at 7A were prepared by dc magnetron sputtering. The films were deposited on to Si(1 11) and glass substrates at room temperature. A 100A thick Al buffer layer was deposited to improve the c-axis orientation. X-ray diffraction (XRD) measurements on the multilayers show a predominant Co-Cr (00.2) peak. Polar magneto-optic measurements were performed to determine the Kerr rotation (OK) and figure of merit. The results indicated an enhancement in the figure of merit at X = 632.8 nm for the multilayered structures compared to single layer samples. All of the films show a 4rMs value around 6 kG and ferromagnetic resonance measurements indicate an enhancement in the perpendicular anisotropy field for the 150A multilayered sample. INTRODUCTION
Since Iwasaki [1] et al. proposed the use of Co-Cr films as perpendicular recording media, numerous studies on Co-Cr films have been performed on a wide range of topics from fabrication methods to film microstructure [2-10]. The positive anisotropy is considered to be one of the basic favorable properties. The magnetic properties are very sensitive to the microstructure, though a clear relationship between them has not been established. The primary problem associated with microstructure is phase segregation. The magnetic properties have been studied by measurement of magnetization curves, torque measurements and ferromagnetic resonance method [7,8]. There are very few reports about the magnetooptic properties of Co-Cr/Al films [9,10]. Co-Cr films prepared by rf diode and dc magnetron sputtering methods show a OK values of 0.0360 and 0.0660, respectively. Recent observation of a large magneto-optic Kerr rotation of 0.4-0.50 for Co-Cr/Al prepared by Facing Target Sputtering (FTS) is very encouraging [10]. In this paper we present the results of magnetic and magneto-optic properties of dc magnetron sputtered single layer and multilayer Co82Crl 8/Al films. EXPERIMENTAL
Samples of Glass and Si (111) were cleaned ultrasonically in acetone and methanol. The Si samples were etched with 10% HF for one minute immediately prior to loading into the deposition system in order to facilitate a hydrogen terminated surface. The samples were deposited in a UHV magnetron sputter deposition system with a rotating substrate holder [11]. The deposition system was evacuated to a base pressure of 4 x 10-8 Torr prior to backfilling with 99.999% pure Ar gas. The samples were deposited using approximately 200 watts dc power at a system pressure of 3.5 mTorr. The target to substrate distance was ten inches. This distance was chosen in order to minimize plasma-
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