A generalized slope model for magnetization transitions

Abstract

Based on a multilayer approach, a generalized slope model is outlined for tape media with arbitrary magnetic layer thickness. A systematic study is performed which includes the role of demagnetization, angle dependence of the switching fields, switching field distribution, particle orientation, particle sizes, and geometric effects such as spacing between head and medium. The theoretical results are compared with experimental ones for high-density digital recording and yield excellent agreement between theory and experiment. Fundamentally, this type of lamina model is found to be incapable of treating magnetic screening effects correctly. In the case of metal evaporated (ME) tape with the easy axis tilted out of the film plane, this turns out to limit the usefulness of multilayer models for nonsaturation recording.

Parametric optimization for terabit perpendicular recording

“…In the three-dimensional (3-D) case (9) and the probability density function for can be obtained from (10) From (9)…”

“…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.…”

Metal Evaporated Media

“…The metal evaporated media are more characteristic of thick granular structures than thin-films, and variations of transition location and transition width are important within the depth of the medium. Extensions of the 1-D models have been proposed to account for the 2D nature of the metal evaporated medium (Cumpson et al, 1997;Jubert et al, 2010;Krijnen et al, 1988;Richter, 1997). The thick medium is assumed to be composed of a discrete number of layers, each layer being thin enough for the thin film approximation to be valid.…”

“…The discussion above gives a phenomenological description of the recording process. To evaluate quantitatively the transition width written into tilted medium, self-consistent macroscopic models have been developed based on the extension of the Williams-Comstock model (Williams and Comstock, 1971) for arbitrary axis orientation (Cumpson et al, , 1997Richter, 1993bRichter, , 1997Stupp et al, 1993Stupp et al, , 1994. The initial developments of the model were 1D Richter, 1993b;Stupp et al, 1993).…”

“…Again the difficulty is to properly take into account the interactions between the layers and the demagnetization fields: each transition within each layer produces a vector demagnetizating field, and the total demagnetizing field is the combination of the demagnetizing fields of all the layers. Different techniques were employed to solve numerically the system of couple equations (Cumpson et al, 1997;Richter, 1997;Stupp et al, 1998). The 2D models allowed calculating the transition profiles properly within the medium depth, with a transition parameter that increases with the distance to the write head (Cumpson et al, 1997;Krijnen et al, 1988;Stupp et al, 1998).…”