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A method of producing a bit-patterned media on a flexible substrate using a low-cost, hot nanoimprinting process is investigated. Using a topographic master with features as small as 40 nm, a flexible plastic substrate is patterned with high fidelity. Magnetic material is sputter-deposited onto the patterned substrate to produce a magnetic tape media with densities as high as 100 Gigadot/in $^{ {2}}$ . Magnetic recording characteristics of the coated bit-patterned tape is evaluated in an apparatus which slides a recording head on the media with a high-resolution positioning capability.

Results of experiments in which hard-disk drive (HDD) tunnel valve (TV) sensors were run in continuous contact with magnetic recording tape are presented. In one mode, suspended HDD sliders were run against tape backed by a supporting air film in a novel configuration. In another, tape was run in an air-skiving mode over HDD rowbars mounted on support beams, similar to the way tape wraps a conventional tape head. The data indicate that HDD TV sensors can successfully operate in continuous contact with running tape media. Measurements show that roughness of older generation metal particle tape limits the signal-to-noise ratio achievable using existing narrow HDD TV sensors. However, TV sensors optimized for running on smoother barium ferrite tape are now a viable candidate for future high areal density tape recording platforms.

The recording performance of a new magnetic tape based on perpendicularly oriented barium ferrite particles was investigated using a 90-nm-wide giant-magnetoresistive reader and a prototype enhanced-field write head. A linear density of 600 kb/in with a postdetection byte-error rate $ was demonstrated based on measured recording data and a software read channel that used a noise-predictive maximum likelihood detection scheme. Using a new iterative decoding architecture, a user bit-error rate of $ can be achieved at this operating point. To facilitate aggressive scaling of the track density, we made several advances in the area of the track-following servo. First, we developed an experimental low-noise tape transport. Second, we implemented an optimized servo channel that together with an experimental timing-based servo pattern enables the generation of position estimates with nanoscale resolution at a high update rate. Third, we developed a field-programmable gate array-based prototyping platform in which we have implemented the servo channel and an $H_{\infty }$ -based track-following controller, enabling real-time closed-loop track-following experiments. Combining these technologies, we achieved a position-error signal (PES) with a standard deviation of 10.3 nm. This magnitude of PES in combination with a 90-nm-wide reader allows the writing and reading of 177-nm-wide tracks at 600 kb/in, for an equivalent areal density of 85.9 Gb/in $^{2}$ . This paper clearly demonstrates the continued scaling potential of tape technologies based on low-cost particulate media.

The magnetic recording performance of perpendicularly oriented advanced metal evaporated (AME) media is studied in a linear tape drive. A modified evaporation process produces the perpendicular orientation, which substantially reduces the writing asymmetry of obliquely oriented AME media in a linear recording environment. While the read back signal exhibits characteristics of perpendicular media, the timing-based servo signal in the drive enables track-following performance with a 1 sigma position error signal (PES) of 0.2 mum . The read channel correctable error rate at the LTO Gen 4 operating point is 10-6 in both the forward and backward directions and the durability of the tape exceeds 100 000 passes without signal degradation.

The recording performance is compared for two barium ferrite magnetic recording tapes which differ by a factor of two in friction, but are otherwise very similar. The error rate of the tapes is similar at a tape speed of 4 m/s, but as the read or write speed decreases to 1.16 m/s, the error rate of the smoother, higher friction tape increases by a factor of 100. This effect arises from velocity variations in the tape, which prevent accurate timing recovery and uncertainty in the phase of the recorded waveform. The velocity variation is measured by recording a periodic waveform. Its power spectrum demonstrates the effect of the compressional sound wave resonating between rollers on either side of the recording head.

Magnetic recording characteristics of a thin-film sputtered media on tape are studied with an HDD head in a high precision nano-positioning system. Signal spectrum roll-off slope is used to determine the effective magnetic spacing to be about 108 nm. The optimum broadband SNR at a linear density of 254 kbpi is 10 dB with a GMR read width of 0.1 mum. The estimated minimum track pitch, limited by side-track interference, is approximately 0.45 mum.