STUDY OF CO-CR FILMS DEPOSITED BY MAGNETRON SPUTTERING UNDER DIFFERENT NITROGEN PARTIAL PRESSURES

Co-Cr alloy thin films are considered to be an applicable perpendicula r magnetic recording medium. The existence of nitrogen residual gas du ring sputtering has significant effects on the structure and propertie s of Co-Cr films. With the increasing of N-2, a phase transformation f rom hcp to fee structure happens gradually when the partial pressure o f N-2 (P-N2) is in the range of 9.6 x 10(-3)-4.0 x 10(-2) Pa, and a tr ansition from tensile to compressive stress takes place. The further i ncreasing of P-N2 stabilizes the fee phase. Finally, when P-N2 is grea ter than 0.23 Pa, a nitride appears with a possible form of (Co1-xCrx) (2)N (where 0 < x < 1). The existence of N-2 degrades the preferred or ientation of crystallines of hcp phase and has detrimental effects on the perpendicular magnetic properties. according to the experimental r esults, a mechanism for the effect of N-2 is proposed. The existence o f N-2 lowers the surface mobility of deposited atoms, and causes the l attice distortion of grains. The transformation from hcp to fee phase is the result of the nucleation and expansion of stacking faults. A me tastable phase with bet (body-centered tetragonal) structure may exist during the formation of fee phase because of the existence of lattice distortion. With the increasing of film thickness, the metastable pha se transforms gradually to the stable fee phase.