Theory of recording on media with arbitrary easy axis orientation

Abstract

By extending the Williams and Comstock model a first order theory of magnetic recording on media with arbitrary easy axis orientation is presented. For a given easy axis orientation a recorded magnetic transition is modeled using three parameters: the transition width, the transition location, and the medium remanent magnetization. By considering media with multiple easy axes the model successfully simulates vector features of the recording process in a medium whose net orientation is longitudinal.

Parametric optimization for terabit perpendicular recording

“…Typically, is a normal distribution and is uniformly distributed between 0 and 2 , so that and (12) after which the hysteresis loop can be obtained by appropriate substitution for in (3) to (8). and are shown in Fig.…”

“…Assuming a linear hysteresis loop of slope , the field required is . The coercivity can be expressed as , where incorporates the angular variation of switching fields as described by (3)- (12). Then (19) and if the head field is limited to , then…”

“…However, the large variations of coercivity and susceptibility with field angle must be taken into account, as the head field varies in magnitude and direction as a function of position. Vector slope models were developed for metal evaporated tape [10]- [12]. We simplify the problem by assuming that in the absence of "tilt" the magnetization is confined to the perpendicular direction, that (30) and that the hysteresis loop can be described by (31) where is as defined by (7) and , the total field, is the sum of external and internal or interaction fields.…”

A Quantitative Multi-layer Recording Model for Media with Arbitrary Easy Axis Orientation

“…The recording model is based on an extended version of the Williams and Comstock model [1] developed by Noyau et al [2] for longitudinal media and on our previous work extending the Williams and Comstock model to arbitrary easy-axis angle. [3] In the model we use a Karlqvist head with a gap width of 0.25 J.il11, and an efficiency of 0.65, to write an isolated magnetic reversal on an ac-erased medium. The write current amplitude is determined experimentally as that which maximizes the measured output signal at a wavelength of 1 J.il11.…”

“…This is in agreement with previous results. [3,5,6] The crossed head field and medium easy-axis condition can be met by either the leading or trailing edge. In the model, writing occurs only at one edge of the head.…”