Micromagnetics study on the noise characteristics in magnetic recording media

Abstract

Micromagnetic treatments of recording physics in the hard disk drive (HDD) can reveal detailed information on the magnetic dynamics during the recording process. The understanding of the medium magnetization process during recording, the write head field, and even the response of magneto-resistive sensors during reproducing process is becoming increasingly important for high end recording achievement in the HDD industry. In order to achieve ultra-high density, it is necessary to make the media with enhanced signal to noise ratio (SNR) characteristics and high thermal stability and to design a writing head which gives sufficiently high writing field and sharp field gradient. In this study, read and write simulations were performed for antiferromagnetically coupled (AFC) media and double layered perpendicular recording media respective with the proper write heads. The SNR and the cause of noise were analyzed. Several modifications and suggestions of the alternative recording systems are proposed and some of them have been checked and proved to improve the noise characteristics of recording system by micromagnetic simulations. Micromagnetic simulations on the AFC media with high antiferromagnetic exchange constant J of 0.9erg/㎠ have been performed for the various thickness and crystalline anisotropy of the bottom layer. In such the strongly coupled AFC media, spin-tilting phenomena occurred for the most part along track in written bits, i.e. magnetizations of each layer are slightly tilted to form magnetization flop in the orthogonal direction to the longitudinal head field. The SNR characteristics of such media are closely related to the degree of spin-tilting. It was also found that head field optimization is necessary in the strongly coupled AFC media to increase signal intensity. The AFC media are an attractive path to postpone the limits of the longitudinal magnetic recording (LMR) In double layered perpendicular magnetic recording media, magnetostatic in...