Magnetic force microscopy of skew angle dependencies in perpendicular magnetic recording

Abstract

Magnetic force microscopy measurements of perpendicular media with a CoCr-based hard layer and a CoFe soft underlayer has been made to investigate skew angle effects. The recorded tracks were produced using a focused ion beam made single pole head with a track width of approximately 400 nm and a gap thickness of approximately 1 μm at a 25 nm flying height. Magnetic force microscopy images of tracks recorded at write currents above and below the saturation value of approximately 100 mA turn were studied at different values of the linear density, 20–100 kfci, at zero skew angle as well as −15° and +15°. Calculated perpendicular recording fields versus the distance down the track, and across the track, near the trailing pole edge was performed using three-dimensional boundary element modeling and compared to the results from the microscopy data. Drawbacks and possible solutions to the skew angle problem for perpendicular recording are discussed.

Perpendicular magnetic recording: Writing process

“…8,35 As mentioned above, unlike in longitudinal recording, for which the recording is produced by the fringing field in the physical gap region of a RH, shown in Fig. 2, in perpendicular recording, the recording is produced in the gap near the trailing edge of the main pole of a SPH, shown in Fig.…”

Micromagnetic Modeling of SNR Performance of Longitudinal and Perpendicular Media With Various Head/SUL Combinations

“…To explain the writing using a longitudinal head on perpendicular media, one needs to resort to the Stoner-Wohlfarth field [12] rather than the perpendicular field component only, as the strong in-plane field is playing a crucial role here. For a perpendicular media grain with anisotropy field , the angle-dependent switching field is given by the criterion (1) where and are the head field components perpendicular to and along the easy axis, respectively, i.e., in-plane and normal to the media film, and is the Stoner-Wohlfarth field. Although in real media there will be a small correction for (1) due to the magnetostatic and exchange interaction between grains, the above criterion gives a first-order estimate.…”

“…First, due to the thickness of the pole tip that is typically much larger than the write gap of a longitudinal head, the head skew at outer diameter (OD) and inner diameter (ID) could cause a side writing band as wide as 100% of the track width at zero skew [1] and, therefore, a significant loss of tracks per inch (TPI). On the other hand, to maintain a good crystallographic structure and, therefore, magnetic property of the media, a thick interlayer between the media and the SUL is usually needed, yielding a large spacing between the head air-bearing surface (ABS) and the SUL.…”

Protein-Based Disk Recording at Areal Densities beyond 10 Terabits/in.2

“…In contrast, erasure of an adjacent track by a stray field or the field generated by part of the recording head is one of the most critical issues in modern magnetic recording technologies. 48…”