Friction and wear properties of Co-Cr media with oxidized surface layer

Abstract

In order to improve the durability of Co-Cr films for perpendicular magnetic recording media, effects of partial pressure of oxygen (Po <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) on the friction and wear properties of Co-Cr films by reactive sputtering in argon / oxygen gas mixture have been investigated. At Po <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> below about 0.08 mTorr, there is no significant reduction of the coefficient of friction (µ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> ) of Co-Cr films, though Cr in the films is selectively oxidized at the column boundary. Above about 0.08 mTorr, sputtered Co-Cr films consist of the oxides of both Co and Cr, and µ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> decreases drastically. In particular, Co-Cr films deposited at Po <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> from 0.1 to 0.2 mTorr take a considerably low value of µ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> and have a good wear resistance. Accordingly, about 200 Å thick Co-Cr film by reactive sputtering at Po <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> of 0.2 mTorr was deposited on the surface of Co-Cr perpendicular magnetic films as a protective layer for Co-Cr flexible disc media. The oxidized surface layer has remarkably improved the wear resistance of Co-Cr media.