Ferrimagnetic Cobalt Ferrite Films Prepared by the Sol-Gel Process
- PDF / 375,655 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 0 Downloads / 261 Views
FERRIMAGNETIC COBALT FERRITE FILMS PREPARED BY THE SOL-GEL PROCESS
EVA M. WONG, HAIXING ZHENG*, JOHN D. MACKENZIE* AND T. TSUCHIYA** .University of California, Los Angeles, Department of Materials Science and Engineering, 405 Hilgard Avenue, Los Angeles, California 90024 **Science University of Tokyo, Department of Materials Science and Technology, Tokyo, Noda, Chiba 278 Japan.
ABSTRACT Ferrimagnetic oxide films have been shown to have potential for use as magnetooptical information storage materials. Cobalt ferrite films are particularly interesting for magneto optical information storage due to their high magneto optical rotation [1]. In this work, synthesized soluble cobalt (II) and iron (III) methoxyethoxides were mixed in stoichiometric ratios for use as Co and Fe precursors in the preparation of CoFe2O4 ferrimagnetic films. The decomposition of the precursors was characterized by thermogravimetric analysis. CoFe,0 4 films were prepared by the dip coating technique using fused silica substrates. These films were then heat treated at temperatures ranging from 200°C to 600°C to study the transformation from an amorphous film to a crystalline film as determined by x-ray diffraction. The magnetic hysteresis behavior of the films as a function of heat treating temperature and hence crystallinity was also studied. As a general trend, films having a greater degree of crystallinity exhibited larger values of saturation magnetization and remanent magnetization. The amorphous film was found to exhibit the highest coercive field, but low values of saturation and remanent magnetization. The effect of heat treating under the influence of a magnetic field of 1.88 kOe was found to enhance crystallization only slightly and had very little effect on the magnetic properties of the film.
INTRODUCTION Materials generally used for magneto optical recording are amorphous rare earthtransition metal compounds, but these materials exhibit low polar Kerr contrast (OK0. 5 °) [2,3]. Advantages are that oxide films have greater corrosion resistance, are very reproducible and are typically less expensive. Amorphous oxide films offer the additional advantage that the absence of grain boundaries reduces media noise [2]. Ferrimagnetic thin films are of interest for a number of novel applications including, but not limited to magneto-optical recording, spatial light modulators and magneto elastic devices. Many deposition methods have been investigated including epitaxial growth [4], spray pyrolysis [3], sputtering [5] and double source evaporation [6], however these methods require expensive and elaborate equipment, continual atmosphere control and long deposition times. NiO and CoO have recently been sputtered by Berkowitz [7] and Fe 30 4 and NiO using reactive MBE by Lind [81 with relatively high deposition rates of 2.0-2.5 Aisec. However, these techniques are still limited to single component systems. Multicomponent systems with controlled stoichiometry can not be easily made. Conversely, sol gel processing can overcome many of the probl
Data Loading...
