Corrosion-resisting Co-Pt thin film medium for high density recording

Abstract

This paper describes a new material medium for high density longitudinal recording. Sputtered Co-Pt thin films will be shown to have excellent corrosion resistance and magnetic properties. Co-Pt thin films do not need a thick overcoat like plated Co-Ni-P films do, and have higher remanent flux density than ferrite thin films. Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Pt <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> (X=0-0.60) thin films prepared by r.f. diode sputtering have a maximum Hc value near X=20. The Hc, Bs and squareness, for 20 at.% Pt film are 1,100 Oe, 12,000 G and 0.80-0.90, respectively, at 0.1 μm film thickness. These values are not changed over 1-15 Watt/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> power densities, corresponding to 6-85nm/min deposition rates. Films with more than 28 at.% Pt have no Bs change after immersion in water for over one month, indicating that the films are passive by this test, at least. Ni additions improve magnetic and corrosion properties. There is no Bs change for Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.070</inf> Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.010</inf> Pt <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.020</inf> films after immersion in water for over one month. Finally, 51 KFRPI linear recording density was obtained, at D <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</inf> , using a Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.70</inf> Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.10</inf> Pt <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.20</inf> thin film disc with a 0.46 μm gap length head and a 0.12 μm head-medium spacing.