The understanding of the mechanisms of magnetic recording systems requires careful measurements. The improvement in both design and fabrication of these devices also necessities thorough experimental investigations. In this dissertation, several key phenomena in magnetic recording are studied experimentally in detail. Issues including the characterization, cause, effect, and avoidance (when desirable) are addressed for each phenomenon. Various experimental techniques are used and new measurement methods are developed and discussed.
An introduction to the magnetic recording channel is given in Chapter 1. The measurement configurations are discussed in Chapter 2. Chapter 3 examines various data averaging and alignment methods, which are crucial to time domain measurements. Investigations on nonlinearities and transition instabilities, both occur at high recording densities, are discussed in Chapter 4 and 5, respectively. Chapter 6 focuses on overwrite in thin film head and disk recording system. An analytical model is given in parallel with the measurements. Noise in thin film media is studied in time and frequency domains in Chapters 7 through 9. Medium noise is correlated and measured autocorrelation functions are discussed for an isolated transition in Chapter 7. Noise is found to be dominated by a few leading noise modes and each mode is associated with a particular physical variation of the signal. Chapter 8 examines the noise autocorrelation functions at high recording densities. Noise behavior is also related to that of the signal, which are discussed is Chapter 4 and 5. Chapter 9 presents a frequency domain analysis along with corresponding measurements of correlated medium noise. The key parameters that govern noise are easily measured in frequency domain using the approach discussed in this chapter.
