Coercivity optimization studies were done on melt-spun nanocomposite Nd 4 R 2 Fe 87Ϫx NbT x B 6 ͑RϭNd,Y,Dy; TϭAg,Cu͒ isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties ͓H C ϭ3.9 kOe, ͑BH͒ max ϭ10 MGOe͔ were obtained by annealing at 750-775°C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the annealing conditions used, Nd 4 Dy 2 Fe 87 NbB 6 samples gave moderate coercivities and in Nd 4 Y 2 Fe 87 NbB 6 samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the presence of Y.
Abstraci -For a high density recording media, the magnetic switching volume is of great importance when considering media noise and thermal stability. CoSdCr films have been prepad and the influence of the Cr underlayer thickness and of the magnetic layer preparation conditions on the magnetic switching volume have been investigated through magnetic viscosity and remnance curve measurements. The measured switching volumes ranged from 3.0 to 15.2x10-'*cm3, and implications regarding noise and thermal stability are discussed.
The magnetic and structural properties of melt-spun Sm(FeT)12 alloys where T=Ti,V,Al,Cu,Ga,Si and with some containing small amounts of B and C have been studied. The samples are magnetically soft in the as-quenched state. High coercive fields are developed upon heating the samples at temperatures ranging from 750 to 1050 °C. The tetragonal ThMn12-type structure was found in all the alloys after annealing. The highest coercivities have been obtained on a Sm10Fe80Ti7.5B2.5 sample with Hc ≂7.7 kOe. These coercivities are much higher than those obtained previously and make these alloys good candidates for permanent magnet development.
Areal density growth has enabled hard disk drives to continually fulfill the demands from new enterprise, desktop, and consumer applications. The demonstration of 100 Gb/in 2 is another milestone that was achieved recently and is described in this paper. The recording demonstration employed fully integrated magnetic recording heads and thermally stable multilayer antiferromagnetically coupled (AFC) media through a commercially available channel chip. At a track density of 149 ktpi and linear density of 680 kbpi, the achieved off-track capability with 5% track squeeze was 10% of the track pitch, while maintaining a raw biterror rate (BER) of 10 4 or better. This yielded an areal density of 101 Gb/in 2 with measured on-track raw BER of 5 10 5 .Index Terms-Disk drives, magnetic heads, magnetic recording, system analysis and design.
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