Barium Ferrite Media Research Articles

Effect of Thermal Conditions on Bit Error Rate for Barium-Ferrite Particulate Media

In this study, the thermal stability of user data written on perpendicularly oriented barium-ferrite media was evaluated in terms of the bit error rate. To determine whether recorded data can be read back after long-term preservation, we recorded a pseudorandom data pattern on barium-ferrite media at a linear density of 500 kbpi and baked the media at 65°C for an extended period. After baking, the recorded data were read back using a 0.45m-wide giant magnetoresistive read head. The bit error rate was calculated using the GPR4ML-AR model. It was found that the bit error rate was stable even after one year at 65°C. This result indicates that perpendicularly oriented barium-ferrite media has high thermal stability.

Planar Thin-Film Servo Write Head for Magnetic Tape Recording

We present a planar thin-film servo write head for writing timing-based servo patterns. The planar head operates at low current ( ~ 100 mA) with nanosecond switching times. The planar head can handle dc current, enabling trailing-edge writing. Magnetic force microscopy measurements of the transitions written by the planar head and a conventional commercial servo write head on longitudinal metal particle and nonoriented barium ferrite media were made to assess the quality of the written transitions. The transition response width PW50 is found to be independent of the tape velocity during write for the planar head. For the conventional head, PW50 is larger and increases with the tape write velocity. The reduced PW50 results in larger readback signal amplitude and hence an improved track-follow performance. The faster switching capability of the planar head enables formatting at higher tape velocity.

6.7 ${\hbox{Gb/in}}^{2}$ Recording Areal Density on Barium Ferrite Tape

We investigated the performance of a barium ferrite tape medium in linear tape recording, using a giant-magnetoresistive read head of 0.5 mum track width. A linear density of 400 kbpi with an error rate of 6 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> was demonstrated based on measured recording data and a simulated channel with advanced noise predictive maximum likelihood detection schemes. Using a timing-based servo format that reduces the position error signal (PES) due to medium jitter and servo-writer velocity variations, we achieved a PES of 0.07 mum standard deviation and a maximum PES (in a 10-s interval) of 0.35 mum. This PES magnitude allows the writing and reading of 1.5-mum tracks at 400 kbpi, for an equivalent areal density of 6.7 Gb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Effects of Cr2O3 or Y2O3 doping in barium ferrite thin-film medium for high-density recording

The effects of Cr2O3 or Y2O3 doping on the surface morphology and magnetic properties in barium ferrite thin films have been studied. Thin films were deposited by co-sputtering a barium ferrite target with a Cr2O3 or Y2O3 target. The deposited amorphous films were homogenized at a temperature of 600 °C for over 10 h followed by annealing at 800 °C in a tube furnace. It was observed that, whereas stoichiometric barium ferrite shows 5000 Å×500 Å acicular grainlike features, films doped with Cr2O3 or Y2O3 had equiaxed topographic features with an average size of 500 Å. Magnetic studies showed that the coercivity of the doped films was over 3500 Oe and was larger than that of stoichiometric films. A weak magnetostatic interaction was found in all the films. Studies of the magnetic after effect indicated excellent thermal stability in all the films.

Texture and interaction effects in barium ferrite media

The nature and strength of the interactions in barium ferrite tapes with different degrees of easy axis texture have been studied by measurement of remanence curves. Easy axis distribution measurements as a function of the squareness have also been made and a correlation has been established between this data and the interactions. The implications of the results for the performance of the tapes as recording media are discussed.

Fluctuation fields of reversal in oriented and non-oriented barium ferrite media

Measurements of time dependent magnetization have been made on samples of partially oriented and nonoriented barium ferrite recording media. From these data and complementary measurements of the irreversible susceptibility, the variation of the fluctuation field H/sub f/ with applied field has been obtained. For the nonoriented sample the variation is quite broad whereas for the aligned case a rapid variation is found. These different types of behavior are attributed to the marked differences in the interaction configurations in the two samples. The interaction in the samples has been characterized via the delta I technique. >

Computation of switching fields of stacked magnetic hexagonal platelet particles

Abstract Switching fields of magnetic hexagonal platelet particles, which were stacked to the easy axis directions, were investigated by computer simulation. The particles had the easy axes perpendicular to the hexagonal planes. The angular dependence of the switching fields became smaller when more particles were stacked and when the particles were stacked closer together. This result is considered as one of the reasons for the small angular dependence of the remanence coercivity of a longitudinally oriented barium ferrite medium. Absence of exchange interaction between adjacent layers in a particle also reduces the angular dependence of the switching field.

Micromagnetic predictions for signal and noise in barium ferrite recording media

A dynamic, micromagnetic recording process simulation is used to predict signal and noise for barium ferrite media. The model has a high spatial (particulate level) and temporal ( approximately=10/sup -9/ s) resolution. The theory includes head saturation, image charge, particle magnetostatic interactions, and particle anisotropy. Most input media and head characteristics are taken from direct measurements, such as electron microscopy or magnetometry, or from the literature. However, several variables, such as head-medium spacing, can only be estimated from the available data; errors in these estimates could affect the predicted numbers by several dBV. Overall, the calculations yield very high accuracy; both signal and bulk erase noise match experiment to within approximately=1 dBV. This unusually close agreement for the bulk erase noise is obtained without the benefit of particle-particle interactions. This latter point places barium ferrite in interesting contrast to acicular particle media where interactions are believed to substantially reduce short-wavelength bulk erase noise. >

Advanced particulate media for high density DASD

Barium ferrite and Co- gamma Fe/sub 2/O/sub 3/ particles comprise the leading particulate media for high-density direct-access storage devices (DASD). The physical, chemical, and magnetic properties of barium ferrite and Co- gamma Fe/sub 2/O/sub 3/ particles and media having film thicknesses of 0.25 mu m are compared. Magnetic and recording properties of isotropic and longitudinally oriented barium ferrite, Co- gamma Fe/sub 2/O/sub 3/, and mixtures thereof confirm its potential for high-density DASD. Linear densities (-3 dB) exceeding 1400 fc/mm were achieved without equalization. Barium ferrite media show both particulate and metal-films noise behavior. >

Magnetic properties and recording characteristics of barium ferrite media

Particle properties i.e., particle diameter, thickness, aspect ratio(diameter/thickness), particle size distribution etc., are important factors governing barium ferrite medium properties and performance. The effects of aspect ratio on saturation magnetization, coercivity, output level, orientability etc. are discussed. Wavelength response for barium ferrite media were investigated, assuming log-normal particle size distribution. Smaller particles with narrower distribution are important for obtaining better short wavelength response and better signal to noise ratio. If aspect ratio is kept constant, an optimum particle diameter exists for maximizing the output at a given wavelength. By comparing perpendicularly, longitudinally and randomly oriented media, perpendicular orientation was found to be prominent in obtaining higher output at submicron wavelengths. Test results show that barium ferrite media are free from corrosion and pressure induced demagnetization. Some barium ferrite media application aspects are also discussed.

Distinctive characteristics of barium ferrite media

Barium ferrite magnetic recording media have demonstrated the capability of achieving much higher recording densities than other particulate media. Even though the best performance is obtained with perpendicularly oriented media, longitudinally oriented and non-oriented Ba-ferrite media also exhibit exceptional recording characteristics. These media have very distinctive magnetic and switching field (SFD) characteristics, exhibiting very small SFD values, almost rectangular remanence loops (indicating no irreversible losses over a wide range of reverse fields), and minor loops very close to the major loop until the driving field becomes almost equal to the coercivity. These unique magnetic and switching field characteristics can explain the very low or negligible demagnetization losses (including recording demagnetization) which we observe in Ba-ferrite media and which result in their outstanding recording performance. The fundamental reasons for these unique magnetic and switching field properties are the predominant high uniaxial crystalline anisotropy of the platelets and their single domain character. On the negative side, the high anisotropy field is directly implicated as the main reason behind the marginal overwrite modulation which characterizes these media.

Micromagnetic recording process simulation

A dynamic model is introduced for simulating the magnetic recording process. This model has high spatial (particulate level) and temporal ( \sim10^{-9} second) resolution. The theory includes head saturation, image charge, particle magnetostatic interaction, and particle anisotropy. Several applications to barium ferrite media are presented.

Digital recording performance of Ba-ferrite media

Barium ferrite media have created a lot of interest for digital and analog applications because of their potential to achieve high recording densities. To fully exploit this potential, it is necessary to develop media with good perpendicular orientation and to employ high saturation narrow gap heads. It is possible, however, to obtain very good recording performance utilizing Ba-ferrite media which are nonoriented or only partially oriented and ordinary ferrite heads for high-density digital recording applications. In this study, we investigated the performance of such media in rigid disk form using conventional and narrower gap ferrite heads, and obtained much better short wavelength response than that obtained from high-coercivity cobalt-modified iron oxide media. The overwrite modulation of these media, however, is only marginally acceptable. The modulation noise observed is much larger for longitudinally oriented than for perpendicularly oriented media. A simple model is proposed to explain the origin of this noise and its dependence on the direction of orientation.

Magnetic contact duplication for R-DAT with Barium ferrite media

The experiments on magnetic contact duplication using a newly developed duplicator for R-DAT (Rotary type Digital Audio Taperecorder) was carried out and evaluated at the wavelength of 0.6 to 40 µm with the track width of 10 to 20 µm. The metal particulate(MP) master tape, barium ferrite(BF) particulate slave tape and Co-γFe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (Co-γ) slave tape were evaluated. (1) The transfer efficiency was about 2 dB greater with the BF medium than with the Co-γ medium. (2) The reproduced wave form of a BF slave tape duplicated from digitally recorded MP master tape was more symmetrical than that of a BF slave tape directly recorded by a recording head. (3) The block error rate of the BF slave tape duplicated by contact duplication was about 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> before error correction. This value indicates that the BF medium is suitable for contact duplication with R-DAT. The above results clarified the superiority of BF medium as a slave tape for contact duplication.