Magnetic Recording Properties Research Articles

Pd/Co multilayers for perpendicular magnetic recording

We have demonstrated that Pd/Co metal multilayers have superior perpendicular magnetic recording properties when compared with conventional CoCr perpendicular alloy media. Using a perpendicular contact probe transducer, the multilayers exhibit more than two times the readback signal of CoCr media. For instance, at 145000 flux changes per inch, multilayer media exhibited a track amplitude of 380 /spl mu/V, compared with 140 /spl mu/V for conventional media using the same transducer. The multilayers can be made with low roughness suitable for contact recording, and can generate narrow 12 microinch readback pulses with large amplitude. In addition, the multilayers have essentially no dead layer. Many aspects of Pd/Co performance can be predictably optimized for a given set of transducer properties.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Laminated media for high-density recording

The magnetic recording properties of laminated media structures on hard disks are discussed, including an overview of work on this topic. The primary performance advantage of laminated media is a significant reduction in media noise. The various mechanisms proposed for this noise reduction are considered. Other issues discussed include the optimal properties for the nonmagnetic interlayers, the influence of lamination on bulk magnetic properties, soft error rate measurements, and process challenges. The most important mechanism for the improved performance that has been obtained is decoupling of the noise sources in the various layers. The optimum interlayer thickness is in the range of 20-50 AA and seems to depend on the sputtering system and process conditions used. >

Magnetic Recording Properties of Double Layered Coating Media

Double-layered particulate media were prepared with excellent magnetic recording characteristics over a wide frequency range. Video luminance signals were recorded only to a depth of 0.3 μm from the tape surface; however, video chrominance signals were recorded to a depth of 0.6 μm from the surface. By utilizing these characteristics, high-coercivity magnetic particles suitable for recording high-frequency signals can be used in the upper layer of the medium. However, performance is affected by the thickness of the upper layer and the coercive force of each layer. Hence these parameters should be chosen carefully, taking into account the recording depths of different signals.

磁性粉の混練，分散状態に及ぼす表面処理の影響

Magnetic paint was produced by using magnetic powder subjected to inorganic or organic surface treatments, in order to make clear the influence of surface treatment exerted on the state of kneading and dispersion. The change of surface characteristic of magnetic powder was estimated from the heat of wetting for organic solvents and the amount of binder absoption. Also, the influences of the degree of surface treatment, water ratio of magnetic powder and the solubility parameter of organic solvent were studied.The state of kneading and dispersion of magnetic powder was evaluated by measuring the mixing torque, glossiness and magnetic recording properties of coated videotape.From the results, the effect of surface treatment for obtaining the well-dispersed state of magnetic powder was clarified.

Magnetic Recording Properties of Spinel Rich Barium Ferrite Tapes

Perpendicularly and longitudinally oriented (PO and LO) tapes were prepared from spinel-rich barium ferrite pigments with different coercivities H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> . The SFD and SFDr for LO tapes were much smaller than for metal particulate (MP) tape. Tape outputs were measured on a drum tester using a Sendust sputtered sheet laminated head. In the low recording density region, the LO tapes yielded higher output than the PO tapes, but at high recording densities, the PO tape output was about 3 dB higher than for LO tapes with nearly the same H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> in the oriented direction. The D <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</inf> of the LO tape was greater than that of MP tape with almost the same longitudinal H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> .

Anisotropy in thin-film media—origins and applications (invited)

The magnetic recording properties of thin-film media are sensitive to a variety of deposition variables. Detailed analyses of these variations generally indicate that the cause of this sensitivity is anisotropy of the films at the microcrystalline level. The origins of anisotropy in thin films are reviewed as are the effects of anisotropy on magnetic recording performance. Applications where anisotropy is used to create enhanced performance for magnetic recording are presented. The problems involved in controlling the microstructural properties of recording media are considered. Finally, strategies to repeatably produce high-performance recording media are presented.

磁気を制御するもの

磁気を制御するもの

Control of parameters in rare earth-transition metal alloys for magneto-optical recording media

The techniques which can be used to control the magnetic and magneto-optical recording properties of sputtered amorphous thin films containing Fe,Co,Tb and Gd are reviewed. It is shown that by proper selection of composition one may independently vary the Curie temperature, the compensation temperature, and coercivity. On-the-other-hand it is shown that the uniaxial anisotropy perpendicular to the film plane and the magneto-optical Kerr rotation are dependent upon the substrate bias and argon pressure used during deposition. A procedure for optimizing the magnetic and magneto-optical properties of these materials for magneto-optical recording applications is outlined. Magneto-optic recording technology today employs amorphous thin films of rare earth-transition metal alloys. The films exhibit a preferred axis of magnetization perpendicular to the plane of the film. At room temperature the coercivity is high so the magnetization remains saturated perpendicular to the film plane, but at high temperatures (> 100°C) the coercivity is low, allowing the magnetization to reverse its direction in local submicrometer regions addressed by a focussed laser beam. To read out the recorded magnetization pattern, the kerr magneto-optic effect is used. This technology allows order of magnitude higher data densities than present rigid disk magnetic recording technology, freedom from head crashes, and removable media. The magnetization of the rare earth-transition metal thin films is determined by antiferromagnetic coupling between the rare earth and transition metal subnetwork magnetizations. Typically at low temperatures the rare earth magnetization dominates, whereas at high temperatures the transition metal magnetization is largest. At some intermediate temperature the two subnetwork magnetizations are equal and opposite resulting in zero net magnetization. At this so-called compensation temperature the coercivity tends toward infinity since there is no net magnetic moment to be acted upon by a magnetic field. At a sufficiently high temperature, the Curie temperature, the net magnetization and coercive force both tend toward zero. In this paper the factors which control the magnetic properties of sputtered GdTbFeCo amorphous films are discussed. Methods to independently control compensation point, Curie temperature, uniaxial anisotropy, and coercivity are explained.

A high orientation effect of cobalt-adsorbed gamma and chromium-dioxide particles for audio recording

Co-adsorbed gamma and chromium-dioxide particles were coated at magnetic fields of O, 1.0KOe, 2.5KOe to investigate magnetic and audio recording properties. We have achieved very high Rs of 91.5% and Br of 1830 gauss for Co-adsorbed gamma, and Rs of 86.3% and Br of 1700 gauss for chromium-dioxide particles coated at 2.5KOe. The increase of MOL(315Hz) was 4.4dB for Co-adsorbed gamma and 3.7dB for chromium-dioxide tape corresponding with the increase of tape Br. But the increase of bias noise level(A-weighted) was only O.6dB and O.7dB respectively.

Relationship of γ-Fe&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;O&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;audio tape properties to particle size

A series of γ-Fe 2 O 3 samples has been prepared and the relationship between particle size and magnetic and audio recording properties studied. The particles ranged in length and width from 0.4 and 0.06 μm, to 0.6 and 0.1 μm, respectively. This corresponds to a variation in calculated volume from 4 to 16 × 10-4μm3. The magnetic and audio recording properties varied significantly with variation in particle size. Tape coercivity decreased from 319 to 241 Oe. Bias noise varied nearly linearly from -68 to -64 dB. Additional correlation of tape properties to particle size is also reported.

Improvements to a self-consistent model for the magnetic recording properties of non-particulate media

Three aspects of self-consistent calculations are considered. The first includes various numerical techniques for reducing by a factor of 60 the running time of the original program. Second, a detailed treatment of the recording characteristics of the thin film head is given. Third, the model is expanded to two dimensions and used to compute with head motion the magnetization vector in a Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> storage medium of moderate thickness. The role of this usually neglected out-of-plane magnetization component is discussed.

Effect of switching field distributions and coercivity on magnetic recording properties

Two series of tapes were coated to investigate the effect of switching field distribution (SFD) and intrinsic coercivity (H ci ) on audio recording properties. In the first series the concentration of γ-Fe 2 O 3 was varied by dilution with α-Fe 2 O 3 . The SFD, which increased with the amount of α-Fe 2 O 3 present, had a large effect on the linear recording range. Signal loss associated with SFD was separated from demagnetization loss. In the second series γ-Fe 2 O 3 was blended with different amounts of cobalt doped γ-Fe 2 O 3 in order to vary H ci . The ratio of short wavelength saturated output to sensitivity expressed in volts was proportional to H ci .