Co-Cr Perpendicular Media Research Articles

Perpendicular Magnetic Recording Medium Optimized for an MR Head

We optimized a perpendicular magnetic recording medium for use with a merged MR head designed for longitudinal media. The dual-layer perpendicular medium with a low-Hc underlayer, has problems in write operation and MR bias current dependence of signal distortion. The single-layer Co-Cr perpendicular medium has similar MR bias current dependence of the signal amplitude and the signal distortion to the longitudinal medium. The Cr content increase from conventional 22% to 28% results the signal to noise ratio increase. The Ti underlayer contributes to increase the recording resolution but not to decrease the medium noise. The Cr-rich Co-Cr perpendicular medium with large thickness and low Ms value is expected to be used with the future high-sensitivity MR head for realizing high-density recording of more than 10 Gbits/inch2.

Noise and ΔM⊥ analysis of a Cr-rich Co-Cr perpendicular medium for an MR head

The medium noise in a Cr-rich Co-Cr alloy perpendicular medium was investigated by using an MR head designed for longitudinal recording. Medium with a Cr content of 28 at.% showed a high crystalline orientation and a low write-demagnetization effect. The signal-to-noise ratio (S/N) of the medium was higher than that of conventional Co-Cr perpendicular media for inductive heads. The advantages of the medium derive from the large inter-particle perpendicular magnetic interaction (/spl Delta/M/spl perp/) of media, which increased linearly with the Cr content, reaching a maximum value at 28 at.%. This strong interaction in the medium results in a high S/N for a recording system using a single-layer perpendicular medium and an MR head.

Co-Cr perpendicular media with semi-soft magnetic and ultra thin back layer for ring-type head

In order to use a ring-type head instead of a single-pole head, a newly designed Co-Cr perpendicular recording medium has been investigated in terms of its recording properties and medium design. A hard disk system with a non-flying metal-in-gap (MIG) head was used for the test. By setting an ultra-thin semi-soft back layer at the back side of the Co-Cr layer, the reproduced pulse shape has been dramatically improved, showing single peak pulses different from the so-called di-pulses obtained for a single-layer Co-Cr medium. This Co-Cr/Fe-Co composite medium was compared with a longitudinal medium of Co-Cr-Ta/Cr with regard to the spacing effect of the output voltage and the density response. The new composite medium showed recording properties superior to those for either the longitudinal medium or a Co-Cr single-layer medium for a very small value of head-medium spacing.

Perpendicular Magnetic Recording Media on Various Hard-Disk Substrates

Co-Cr perpendicular media on rigid substrates were studied. We used untextured glass substrates for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard disk media deposited onto different substrates: untextured glass, silicon single crystal, chemically textured alumite, and Mn-Zn ferrite. We compared these substrates with respect to their crystallographic properties, head-to-medium spacing, and record/playback characteristics.

垂直磁気ハードディスク媒体における基板の検討

Co-Cr perpendicular media on rigid substrates were studied. We used a non-texturing glass substrate for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard-disk media deposited on different substrates, namely, non-texuring glass, silicon monocrystal, chemically textured alumite, and Mn-Zn ferrite. We compared those substrates from the viewpoints of crystallographic properties, head-tomedium spacing, and recording and reproducing characteristics.

ANALYSIS OF UNUSUAL TRANSITION OF Co-Cr MEDIUM IN SINUSOIDAL WAVE RECORDING USING RING HEAD

The Co-Cr perpendicular medium shows superior recording characteristics using a ring head. We observed an unusual reproduced waveform for a transition in sinusoidal recording which is quite different from a usual dipulse. The phenomenon became apparent with lower recording current levels and longer wavelengths. The waveform of the unusual transition was analysed using a waveform transition based on the Hilbert transformation. We determined that the transition consisted of one main pulse followed by two sub-pulses. We propose a simple model for the unusual transition.

CoPtB(O) alloy films as new perpendicular recording media

In search of new hard magnetic materials with high saturation magnetization and large coercivity, a comprehensive study was made on numerous Co- and CoPt-base crystalline alloys by means of sputtering techniques. It revealed that a newly found CoPtB(O) alloy system possessed excellent hard magnetic properties with remarkably large perpendicular coercivity and high saturation magnetization. This new alloy film, deposited onto room temperature substrates, shows the magnetic properties of 4πMs=12 kG, H⊥c=4000 Oe, and perpendicular anisotropy field Hk=22 kOe. These values are superior to those of prevailing materials such as CoCr perpendicular and CoPt or CoNi longitudinal recording media. The typical composition is Co69Pt20B6O5 (at. %), and oxygen plays a momentous role on the coercivity in this alloy film. As a magnetic recording medium, a write/read experiment of this film shows that the readout signal has a +9 dB peak-to-peak amplitude compared with that of metal particle tape at 1 μm wavelength and has +10 dB compared with that of a CoCr perpendicular medium at 0.5 μm wavelength.

Corrosion rate activation energy of sputtered CoCr perpendicular media

Corrosion rate activation energy ΔE has been evaluated by measuring electrical resistance increase due to corrosion for CoCr (0 ∼ 26 at%Cr) film stripe patterns under exposure to various temperatures and 85% relative humidity. A relation of corrosion layer thickness X to Cr density x, test temperature T and test time t were obtained. The relation was expressed by X = C \cdot \exp(-\gamma \cdot x) \cdot \exp(-\Delta E/k T)\cdot \log(t+l) , where K, γ and C are the coefficient and Boltzmann's constant,respectively. ΔE values for CoCr films (0∼ 26 at%Cr) depend upon Cr density and preparation conditions. These values ranged from 0.075 to 0.32 eV. Corrosion characteristics are varied by not only film microstructure, but also to Cr atom distribution in crystalline matrix even for films with same Cr density.

Magnetic properties of vacuum deposited Co-Cr perpendicular media and their recording performances

To clarify the magnetic properties required for the continuously vacuum deposited Co-Cr single layer media, the dependence of reproduced voltage using the ferrite ring heads on Hkeff, Hc\perp , Ms and thickness is studied. The media with Hkeff of 2 - 4.5 kOe, Hc\perp of 500 - 700 Oe, Ms of 300 - 600 emu/cc and thickness more than 0.2 μm yield high reproduced voltage and high CN ratio at high linear density over 100 kFRPI. Even the media with Hc\perp less than 200 Oe have high reproduced voltage, but media noise is high too. Besides the above factors, it is found that the shearing of the perpendicular hysteresis loops measured by VSM affects the recording performances. The shearing slope of the loops is about 1/3\pi for the perpendicular anisotropy media which have high reproduced voltage at high linear density. The CN ratio of 45 dB is obtained at 130 kFRPI by use of a narrow track ferrite head with track width of 5 μm at the medium-head relative speed of 3 m/s.

Wear resistance, mechanical strength and microstructure on sputtered CoCr perpendicular media

Wear resistance for sputtered CoCr perpendicular recording media has been investigated. Wear resistance and mechanical strength (tensile strength and Young's modulus) have been measured for CoCr (0-33 at% Cr) films deposited under various sputtering conditions. Furthermore, their correlations to CoCr film microstructures have been studied. The wear resistance on the CoCr films strongly depends upon the mechanical strength, and their relationship can be explained in terms of Archard's adhesive wear theory. Wear resistance and mechanical strength for CoCr (5-33 at% Cr) films decrease steeply at high sputtering Ar pressure. However, those for pure Co films are independent from sputtering pressure. Microstructure analyses for CoCr and pure Co films indicate that a main factor reducing the wear resistance and the mechanical strength is Cr segregation in the CoCr films.

Internal Stress of Co-Cr Perpendicular Media

Internal Stress of Co-Cr Perpendicular Media