Tomoko Taguchi

Quantitative MFM study on partial erasure behavior of longitudinal recording

In this paper, we propose a new MFM (magnetic force microscopy) method to analyze the probability and size of partial erasure (PE). An analysis classifying the linear and nonlinear partial erasure is also proposed. It was realized that the nonlinear PE is correlated with the inter-granular magnetic coupling in thin film media. The isolation of the magnetic coupling was found effective to reduce the nonlinear PE.

The effects of head configuration on write resolution for submicron track recording

This paper presents a study of track edge writing phenomena with a view to achieving submicron track width longitudinal recording. Side written bands made by 1 /spl mu/m wide high-Bs FeTaN heads were compared with those by conventional NiFe thin film heads with the same width. Off-track overwrite experiments revealed that the balanced condition of the narrowed write gap and strong head fields by high-Bs poles suppressed the width of the degraded side written band and excessive erase band forming near the track edges. An analytical write modeling considering the non-saturation side writing process also showed that optimized narrow write gap along with strong head fields improved the write resolution throughout the narrow track.

Analysis of Effective Field Gradient in Microwave-Assisted Magnetic Recording

Microwave-assisted magnetic recording (MAMR) is one of the promising techniques for future high recording density hard disk drives. In this paper, we estimate the effective field gradient in MAMR using the relation between recorded transition length πa and field gradient by dynamic write process simulation. The effective field gradients reach 600 and 700 Oe/nm on each optimum field generation layer (FGL)-position and FGL oscillation frequency when the microwave field strength (c - Hac) are 700 and 950 Oe, respectively. These results indicate extremely high linear density would be possible by MAMR.

Trilayer media for high track density longitudinal recording

This paper introduces a new recording method using a trilayer medium (recording layer/nonmagnetic layer/soft magnetic layer/substrate) to diminish the side written band width (ΔW). Magnetostatic coupling between the soft magnetic layer in the media and the write head poles decreases the side fringing field off the track edges. Off‐track overwrite experiments revealed that the trilayer media reduced ΔW by 40%–60% compared to the monolayer medium while maintaining the effective write track width and the linear resolution.

Characterization of GMR nonlinear response and the impact on BER in perpendicular magnetic recording

The giant magnetoresistive (GMR) reader nonlinear response in perpendicular magnetic recording should be characterized and studied for the impact on bit-error-rate (BER) performance, because a waveform of perpendicular recording is influenced by GMR nonlinearity differently from longitudinal recording. In this study, the read/write characteristics and BER performance under the influence of GMR nonlinearity were investigated. For a GMR saturation parameter, the amplitude ratio of the fifth harmonic spectrum of isolated patterns to same spectrum of di-bit pattern was measured. This saturation parameter is a good indicator to estimate GMR saturation. GMR asymmetry has a different impact on BER performance from GMR saturation. The raw isolated waveform of perpendicular recording is inappropriate to estimate GMR asymmetry because it does not indicate an accurate dc-ground level with the low-frequency cutoff channel. A specific test patterns which can provide dc-ground level, was found. The measured asymmetry of this test pattern correlates closely with the asymmetry of measured GMR transfer curves. The peak shift of a differential waveform is also a good indicator to estimate GMR asymmetry. Signal processing simulation and some measurement results showed BER performance is influenced by GMR nonlinear response. The impact of GMR nonlinearity on BER depends on their feature. GMR asymmetry has a strong correlation with BER performance.