Texture noise and its impact on recording performance at high recording density

Recent advances in the recording physics of thin-film media

“…This holds for both longitudinal and vertical magnetization transitions. Equation (43) states that the effect of head to medium spacing (d) and transition sharpness (a) on the readback signal is identical. This means that one cannot measure the transition sharpness directly; only in conjunction with careful head to medium spacing measurements (which are very difficult to accomplish), one can deduce values for the transition sharpness.…”

“…The density of these texture lines is in the order of 100 mm −1 , but they are only a few nanometres deep. For modern thin-film media, the surface roughness caused by the texture is so small, that the texture-induced noise does not have an impact on recording [43]. The wavelength of the texture is much longer than the wavelength of the recorded information.…”

“…On the other hand, the recording head itself is too slow to respond to the topography changes and maintains a constant flying height. Thus the head-to-medium spacing, d, is modulated, which leads to a band-pass modulation at read back due to the spacing loss, exp(−kd) [43]. Similar to a conventional amplitude or phase modulation, the bandpass modulation leads to side bands on either side of the 'carrier'.…”