Magnetic recording media used today are based on sputtered cobalt alloy films with thicknesses in the order of 50 nm. As recording density is increased, the microstructure of the film must be controlled with increasing level of sophistication to achieve the magnetic properties necessary for good recording performance. Recording density has been increasing at the compound annual rate of 30%, and in recent years at a higher rate. Already, 1 Gb/in2 has been achieved in the laboratory [1], and 10 Gb/in2 is being contemplated [2]. In order to achieve such densities, microstructural characteristics such as grain morphology, size distribution, crystallographic orientation, and grain separation must be controlled with great precision, and their relationship to magnetic properties must be understood. The paper will describe the effect of sputter process conditions and the selection of magnetic alloys on the film microstructure and describe what might be required to achieve high recording densities. Particular attention will be paid to grain size distribution and grain separation. Grain separation is important for low noise performance of the media. Alloy selection and sputtering conditions can be manipulated to achieve different levels of separation between the grains.
In thin film magnetic media, the magnetic hysteresis properties and micromagnetic domain behavior are strongly influenced by both interparticle exchange interactions and by magnetostatic interactions. The exchange interactions are short-range in nature; therefore, they are very sensitive to interparticle separation. Consequently, the magnetic hysteresis properties and the recording behavior of the thin film magnetic media can be drastically altered by the introduction of grain separation during the film deposition process. In this study, thin film media of a CoNiPt alloy of one composition was processed under two different conditions. Transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HRSEM) were used to investigate and explain the difference in magnetic hysteresis characteristics of the films.The structure of the thin film media consisted of a 600 Å thick CoNiPt alloy sputtered on textured 130mm diameter NiP-plated aluminum substrates. A single sputtering parameter was varied to produce two types of films, labelled type I and type II, which exhibited significant differences in their magnetic recording characteristics.
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