Thin Film Recording Media

Abstract

The rapidly growing demand for magnetic information storage systems at lower cost and higher capacity has driven the magnetic recording industry to accelerate development of thin film magnetic recording media. The ultimate recording density depends on the bit transition lengths, as shown in Figure 1 for various media, and on signal-to-noise ratio, which is proportional to the number of particles per bit. Longitudinal thin film media bit transition lengths are limited by thickness, magnetic properties, and zig-zag magnetic domain microstructures at the transitions, whereas in perpendicular media the principal limitation is the diameter of the grains. The recent development of quasi-particulate longitudinal and perpendicular thin film media indicates that areal bit densities substantially exceeding 109 bits/inch2 will be achieved in the future.This article will review magnetic phenomena relevant to thin film recording media, describe macromagnetic and micromagnetic characterization techniques, survey the development of state-of-the-art thin film media, correlate micromagnetics with magnetic properties, media noise, and recording performance, and discuss future requirements of longitudinal and perpendicular thin film recording media.Ferromagnetic and ferrimagnetic thin films exhibit a nonlinear, multivalued, and hysteretic relationship between the magnetic dipole moments per volume or magnetization M and the magnetizing field intensity H as shown in Figure 2 for the component of M in the direction of H.