Distinguishing Random and Spatially Deterministic Noise Components in Heat-Assisted Magnetic Recording

By averaging multiple writes of opposite polarity waveforms captured synchronously from heat-assisted magnetic recording (HAMR) media, we distinguish random noise of the HAMR writing process from the spatially anti-correlated repeatable noise due to media microstructure variations. We show both analytically and experimentally how the normalized cross correlation coefficient, R, of two opposite polarity waveforms quantifies the random and repeatable dc-noise fractions, showing where dc-noise reduction efforts should be concentrated. The value of R also reflects the degree of media saturation. At optimal recording conditions for the head and media studied here, the total dc-noise comprises appreciable fractions of both random and repeatable noise. The experimental results are supplemented with micromagnetic modeling and analytic calculations.