Digital signal evaluation for a thin-film single-pole head and double layer perpendicular disk was carrited out with an error rate tester. An AMR head was used as a reading head. The channel of the tester was the PR4ML with the 8/9 endec. Waveform for the MR head was transformed with a differentiator consisted of passive LCR circuitry and high speed linear amplifier. A D50 of 185 kFRPI, a PW50 of 130nm, and an NLTS at 300 kFRPI were measured. A byte error rate of 10^<-6> was obtained at 310 kFRPI for a read trackwidth of 1.4μm.
"High Density Recording" has been a main stream in magnetic recording. Another recent stream is "High Frequency Recording". It is not enough to analyze only magnetic fields in high frequencies above 500MHz. Electromagnetic field analyses considering the capacitances among conductors and between lines are required. We will report the basic principles and application examples of numerical analysis methods such as FEM, finite element method, and FDTD, finite difference time domain, to high frequency magnetic recording heads.
Spin-valve-like ferromagnetic tunnel junctions with Fe-Mn pinning layer were fabricated by magnetron sputtering using metal mask. As insulator barrier layers, Al layers were oxidized by methods of natural oxidization and plasma oxidization. The junctions showed spin-valve-like R-H properties in both cases, and MR ratio of 24% were obtained by 300 Oe, 1 hour annealing. We can fabricate junctions more quickly in plasma oxidization compared to natural oxidization.
The magnetically super resolution (MSR) and magnetic amplifying magneto-optical system (MAMMOS) have been proposed for high area-density recording above 10Gbit/in^2. These disks need multi-layer structure in principle, therefore interlayer phenomena of each layer is important. Readout power, recording power, readout signal-output, readout magnetic bias field etc., as a concern of each layer and layer-interaction, were inspected in MSR and MAMMOS disks. As integrating inter-relations of each layer, we could acquire the main conditions, which are layer thickness and composition, etc. And, as a result, we recognized that flow of heat, exchange force, magneto-static force, coercive force and thickness of non-magnetic intermediate layer were important.
A single chip encoder was developed including many functions for consumer application use. The main features are as follows : 1) Wide search range motion estimation, H±288 pixels, V±96 pixels. 2) Required external circuitry is only 32Mbit SDRAM. 3) Internal DSP controller to handle system and rate control. 4) Encoding NTSC and PAL image for MP@ML up to M=3. 5)Robustness against signal jitter. 6) Constant length coding for each GOP. 7) Auto detection of 3-2 pull down signal and 3-2 pull down inversion. 8) Temporal noise reduction, Scaling and Image cropping. The chip was designed using 0.4um CMOS process technology, the chip size is 13.7mm×12.4mm with 4.5M Tr and the power consumption is 1.2W at 3.3V.
The performance comparison of the various PRML systems for (1,7) RLL code, 8/9(0,4/4) code and 16/17(0,6/6) code is studied. The bit-error rates of PR4ML, EPR4ML, E^2PR4ML, ME^2PR4ML, PR(1,2,1,-1,-2,-1)ML and PR(1,2,1,0,-1,-2,-1)ML systems are obtained by computer simulation and the relationships between the reduction parameter in partial erasure and the required SNR are studied. The results show that PR(1,2,1,-1,-2,-1)ML system exhibits the good performance for (1,7) RLL code, and PR(1,2,1,0,-1,-2,-1)ML system offers the excellent performance for 8/9(0,4/4) code and 16/17(0,6/6) code.