The recording performance of a new magnetic tape based on ultra-fine, perpendicularly-oriented BaFe particles was investigated. Specifically, using a low lateral tape motion demonstration platform, a new servo pattern written on the advanced perpendicularly oriented BaFe medium, a new low friction head technology, a novel synchronous servo channel design, and advanced servo control concepts, we were able to demonstrate a record closed-loop track-follow performance with a 23.4 nm standard deviation of position-error signal, roughly one order of magnitude better than in current tape products. In addition, using read back waveforms captured on the same advanced perpendicularly oriented BaFe medium with a 0.2-m-wide data reader, we demonstrated write/read performance at 518 kbpi using advanced noise-predictive maximum likelihood (NPML) detection schemes. Combining these two results, we estimate that the new medium can support an areal recording density of up to 29.5 Gb/in 2 . This result demonstrates the scalability and extendability of tape technology using low-cost particulate media.

We report the first high-field x-ray diffraction experiment using synchrotron x-rays and pulsed magnetic fields exceeding 30 T. Lattice deformation due to a magnetic-field-induced valence transition in YbInCu4 is studied. It has been found that the Bragg reflection profile at 32 K changes significantly at around 27 T due to the structural transition. In the vicinity of the transition field the low-field and the high-field phases are observed simultaneously as the two distinct Bragg reflection peaks: This is a direct evidence of the fact that the field-induced valence state transition is the first order phase transition. The field-dependence of the low-field-phase Bragg peak intensity is found to be scaled with the magnetization.

The magnetic field-induced valence transition in YbInCu 4 has been studied by X-ray absorption spectroscopy at the Yb L III -edge up to 41 T. The field-induced valence transition is clearly observed as a significant change in the absorption spectra. Magnetic field dependences of Yb valence at low temperatures are directly determined for the first time. It is found that the valence above the metamagnetic transition recovers from Yb 2:84þ to Yb 2:96þ which is identical to that in the hightemperature phase. Variation of the valence is also obtained in the B-T (magnetic field-temperature) plane at 0 < B < 41 T and 5 < T < 50 K.

No abstract

The recording performance of a new prototype magnetic tape based on perpendicularly oriented strontium ferrite particles is investigated using a 29 nm wide tunneling magnetoresistive reader. At a linear density of 702 kbpi, a post-detection byte-error rate of 2.8e-2 is demonstrated based on measured recording data and a software read channel. The read channel uses a 64-state implementation of an extended version of a data-dependent noise-predictive maximum-likelihood detection scheme that tracks the first and second order statistics of the data-dependent noise. At the demonstrated post-detection byte-error rate, a post-error-correction-coding byte-error rate of less than 1e-20 can be achieved using an iterative decoding architecture. To facilitate aggressive track-density scaling, we made multiple advances in the area of track following. First, we developed a new timing-based servo pattern and implemented a novel quad channel averaging scheme. Second, we developed a new field programmable gate array prototyping platform to enable the implementation of quad channel averaging. Third, we enhanced our low disturbance tape transport with a pair of 20 mm diameter air bearing tape guides and a prototype track-following actuator. Fourth, we developed a novel low friction tape head and finally, we designed a set of tape speed optimized track-following controllers using the model-based H∞ design framework. Combining these technologies, we achieved a position error signal (PES) characterized by a standard deviation ≤ 3.18 nm over a tape speed range of 1.2 to 4.1 m/s. This magnitude of PES in combination with a 29 nm wide reader enables reliable recording at a track width of 56.2 nm corresponding to a track density of 451.9 ktpi, for an equivalent areal density of 317.3 Gb/in 2 .