Approximate Expressions for the Magnetic Potential and Fields of 2-D, Asymmetrical Magnetic Recording Heads

Abstract

Two-dimensional asymmetrical magnetic head are characterised by parallel inclination of the semi-infinite, inner gap walls, and where the gap length and head-to-underlayer separation are small compared to the other dimensions in the head. With head corner inclination, these structures contribute to reduction in the effective gap length of the head and therefore increase in the field magnitude and narrowing of the field distributions near the acute gap corner. Asymmetrical heads were therefore proposed for increasing the writing and readout resolutions in gapped magnetic head structures. There are currently no explicit or approximate analytical solutions for the potential and fields from two-dimensional asymmetrical magnetic heads. This paper is concerned with the detailed theoretical derivation of relatively simple closed-form approximations for the scalar magnetic potential and fields from twodimensional asymmetrical magnetic heads and their Fourier transforms, applicable to any arbitrary corner inclination angle. A general theory based on the translated Sine Fourier series is developed to model and study the reaction of a soft magnetic underlayer (SUL) on the surface potential of any magnetic head structure, and applied to the asymmetrical head. The approximate potential and field expressions derived in this paper demonstrated very good agreement with finite-element calculations of two-dimensional asymmetrical heads.

Frequency Response of a Moving Two-Dimensional Defect in Magnetic Flux Leakage Inspection

“…Asymmetrical (tilted) defects with small tilt angles can still produce detectable width nulls in the leakage field spectrum due to the large concentration of charges in the corner regions. However large tilt angles can lead to reduction of the effective defect width and smearing of the nulls in the frequency response [Aziz et al 2016b]. Further investigation is needed to understand the dependence of the frequency response of the leakage fields from asymmetrical defects with finite depth and realistic charge distribution on the tilt angle.…”

Theoretical Analysis of Gap Potential Functions and Corner Saturation in 2-D, Symmetric Magnetic Recording Heads With Tilted Gap Corners

“…In this case the gap length is assumed small compared to the other head dimensions (cross-track width and throat height). The effect of a soft underlayer is not included in this paper due to limited space, but can be easily modeled using the integral transform theory developed by the authors in [15] to determine the reaction of the underlayer on the magnetic potentials and fields for any head geometry. The boundary value problems solved in this work are all based on static scalar and vector potentials since the focus is on field mapping and characterising corner saturation and its dependence on corner angle, and therefore transient effects are ignored.…”

Optimization of Asymmetric Magnetic Recording Heads Inclination Angle and Study the Characteristics for a Higher Bit Density Recording of HDD

“…Two-dimensional geometry of the asymmetrical head, with gap length g, exterior corner inclination angleqo and poles potentials ±U0(Aziz et al, 2016).…”