MAGNETIC INTERACTION AND REMANENCE PROPERTIES IN CONIPT(SIO2) GRANULAR FILMS FOR HIGH-DENSITY LONGITUDINAL RECORDING

Magnetic interaction and remanence properties in (Co81Ni7Pt12)(100-x)( SiO2)(x) films (x=0-8) have been studied for high-density longitudinal recording. Films with SiO2 contents of 6 and 8 mol %, in which suffic iently isolated CoNiPt grains with a diameter of about 10 nm and a ran dom orientation of the c axis of hcp structure are observed, show a si gnificant low-noise property as well as high coercivity. Both frequenc y dependence of the media noise and magnetic domain structure in the r emanent-magnetized state show that the exchange interaction between gr ains is eliminated by the grain boundary of the SiO2 phase with the wi dth of 2 nm. In such films, high coercive squareness of 0.9 on the rem anence curve is obtained, while the squareness on the hysteresis curve decreases as the SiO2 content increases. Henkel plot indicates that ' 'ferromagnetic'' interaction among the grains sustains such high squar eness on the remanence curve, The strength of the interaction depends on the film thickness and is proportional to the squareness on the rem anence curve. The origin of the ''ferromagnetic'' interaction among gr ains is discussed, mainly based on the magnetostatic interaction. (C) 1996 American Institute of Physics.