Very Thin Protective Film of Fe-Mo-B Based Hard Alloy for Curl-Free Magnetic Tape
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VERY THIN PROTECTIVE FILM OF Fe-Mo-B BASED HARD ALLOY CURL-FREE MAGNETIC TAPE
FOR
SETSUO AKIYAMA, N.MATSUSHITA, S.NAKAGAWA and M.NAOE Dept. of Physical Electronics, Tokyo Institute of Technology, 2-12-1 0-okayama, Meguro-ku, Tokyo 152, Japan
ABSTRACT Tribological troubles and tape-curling of perpendicular magnetic Thin films of a wear recording tapes are critical for their practical use. resistant and electrically conductive Fe-Mo-B based alloy were prepared on method tape substrates by the facing targets sputtering (FTS) plasma-free for applying them as protective layers in the magnetic tapes. The films were The alloy very flexible and almost non-magnetic. perfectly amorphous, molybdenum atoms at a concentration as targets for these films contained The Mo atomic weight is higher than that of working gas high as 24 at%. Accordingly, not only Ar but also Kr atoms were recoiled atoms Ar and Kr. from the target planes and then bombarded the growing layers to cause large compressive stress in the deposited films. Therefore, these protective films must be very thin to avoid tape-curling. Protective films as thin as 100 A could largely reduce the dynamical friction coefficients of the surfaces additioq of magnetic tapes owing to the hardness of their ceramic phase. In to this merit they possessed electrical resistivity as small as 1.2x10Q.cm. owing to their metallic binder phase. Consequently they are'applicable as protective layers of curl-free magnetic tapes.
INTRODUCTION magnetic recording systems with ultra-high density such as the In the spacing perpendicular one for the high definition television (HDTV), between head and tape must be extremely decreased and tribological accidents such as a headcrash are apt to happen. One of the subjects required for putting the perpendicular magnetic recording tape with Co-Cr thin film into practical use is to prevent tribological troubles on the tape surface. Therefore the magnetic tape surface must be protected by a thin layer of electrically conductive and wear-resistant material with extremely small for preventing frictional fragments of the medium friction coefficient since surface from clinging to the head through static electrical effect, these sticking fragments on the head wear out the tape surface fatally. required for the practical use of the perpendicular Another subject tape with a Co-Cr recording layer is to suppress the curling of magnetic Thin films deposited by sputtering method possessed the magnetic tape. internal stress which caused the apparent curling of magnetic tape composed of deposited films and substrate, because tape substrates must be thin to attain higher volume recording density. It is important to control the internal stress 0t in the deposited films in order to avoid curling of the magnetic tape, since significant tape curling prevents the tape from moving smoothly and from making good contact with the sliding plane of the head. Not only the Co-Cr recording layer but also the protective layer may cause tape-curling. The authors have developed a
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