Noise characteristics of recording media become more important as the density of magnetic recording is ever increasing. In this thesis, recorded bit patterns and noise characteristics of longitudinal magnetic recording media have been studied by adopting numerical micromagnetic model.
For this purpose, three different kinds of recording media is studied; a well-oriented film with an unique anisotropy constant, an isotropic film with an unique anisotropy constant and a well-oriented film with varying anisotropy constants of a gaussian distribution. For those three different media, no exchange coupling and weak exchange coupling assumption between grains are considered.
Multiple bit patterns are simulated by head fields and magnetic properties of media are analyzed statistically. Magnetization pole densities in recorded bit are calculated as well as magnetization patterns.
In the well-oriented film with an unique anisotropy constant and no exchange coupling case, it is found that the transition extends significantly to track edges, and this trend becomes more severe in the case of the medium of weak exchange coupled grains. There are shifts of transition position along the track edge and such shifts result in a broadening and shifting of read-back voltage. Magnetic moments in the track edge are in saturation magnetization states, which is expected to serve as a noise source of a cross talk type in the case of a narrow track recording. The noise within bit is concentrated at the transitions, namely transition noise.
In the isotropic film with an unique anisotropy constant, the recorded transition does not extend to the recording track edge unlike the previous medium. When a bit is written in this medium some cells not within the head gap are also magnetically reversed by the head fields, unlike the previous medium. However, these patterns are expected to be erased easily as the cells are not in saturation magnetization states. Transition noise of this medium is lower than that of the previous medium but edge noise seems higher in this medium as the noise more widely.
For the well-oriented film with varying anisotropy constants in gaussian distribution, a rectangular type bit with very small V-type patterns at bit edges is found and the medium noise is concentrated at the transitions.
