Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
2000-09-01
2003-06-24
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
Disk
Reexamination Certificate
active
06583958
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium and a magnetic storage system which are capable of recording a large amount of information and, more particularly, to a magnetic recording medium suitable for high-density magnetic recording and a magnetic storage system in which this magnetic recording medium is used.
Needs for large-capacity design of magnetic storage systems are growing more and more. In recent years, to meet the needs, it has rapidly proceeded to adopt a composite type head in which a writing head and a reproducing head are separately provided and in which a highly sensitive magneto-resistive head is used as the reproducing head. Further, a more highly sensitive head has also been put to practical use. In this more highly sensitive head, in order to increase the sensitivity of a magneto-resistive head that utilizes a change in the electric resistance of elements caused by a change in the leakage flux from a medium, there is utilized a very large magnetoresistance change (giant magnetic resistance effect or spin-valve effect) occurring in a plurality of magnetic films layered via a non-magnetic film. This head utilizes the phenomenon that the relative magnetization direction of a plurality of magnetic films layered via the non-magnetic film is changed by a leakage magnetic field, resulting in a change in magnetoresistance.
On the other hand, as requirements for high-density design of magnetic recording mediums, a noise reduction and a reduction in a regenerative output change occurring with the lapse of time due to thermal fluctuations are necessary.
In order to realize a recording density exceeding 20 Gb/inch
2
in a magnetic disk medium, it is necessary to increase coercivity and besides to reduce the unit of magnetization reversal occurring in a magnetic film. For this purpose, it is necessary to make magnetic grains fine in size which constitute the magnetic film.
JP-B-2674131 discloses a thin magnetic film which is expressed by a composition equation (Coa Ptb Bc Mä)100−x Ox (where a, b, c, &dgr;, x are atomic %), and has composition ranges of:
0
<a=
100
−b−c−&dgr;;
0
<b≦
50;
0.1
≦c b≦
30;
0<&dgr;≦30;
and
0≦
x≦
15
where, the above M is at least one kind selected from the group consisting of Ti, Zr, V, Cr, Nb, Mo, Ta, W, Fe, Ni, Si, Al, Ge, Ga, In, Sn, Pb, Sb, Bi, P, Se, C, Zn, Cu, Ag, Au, Ru, Pd and Re.
As an example in which this thin magnetic film is applied to a magnetic recording medium, JP-A-2-73511 discloses a CoPt-base alloy or CoPto-base alloy magnetic recording medium which has a thin magnetic film containing B or at least one kind selected from the following group of elements MI, wherein the above thin magnetic film is formed on an underlayer which contains at least one kind selected from the following group of elements MII and has a thickness of 1 to 1×104 nm (1×10 to 1×105 Å). The thin magnetic film contains, as the above elements MI, at least one kind selected from the group consisting of Ti, Zr, V, Cr, Nb, Mo, Ta and W and, the underlayer contains, as the above elements MII, at least one kind selected from the group consisting of Ti, Zr, V, Cr, Nb, Mo, Ta, W, Hf, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Ti, C, Si, Ge, Sn, Pd, P, As, Sb, Bi, S, Se, Te, Be, Mg, Ca, Sr, Ba, Sc, Y and rare-earth elements.
Further, there is proposed in JP-A-60-228637 a Co-base alloy for magnetic recording medium's which contains Cr in an amount of 9.0 to 22.5 wt., %, at least one kind selected from the group consisting of Sc, V, Nb, Ta, W, Mn, Tc, Re, Fe, Os, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ca, In, Tl, C, Si, Ge, Sn, Pb, P, As, Sb, Bi, S, Se, Te, lanthanoid elements and actinoid elements in an amount of 0.001 to 5 wt. % in total, and the balance Co.
SUMMARY OF THE INVENTION
The technology described in the above JP-B-2674131 relates to a perpendicular magnetic recording medium and was unsuitable for longitudinal magnetic recording because of a larger perpendicular coercivity than a longitudinal coercivity. Further, in the conventional technology described in JP-A-2-73511, there is proposed a medium structure for improving perpendicular coercivity, longitudinal coercivity or perpendicular magnetic anisotropy. However, when a magnetic recording medium was formed by optionally selecting Cr and Ru, respectively, from the above element groups MI and MII, it was difficult to reduce medium noise and hence it was necessary to further reduce the noise. Further, there was a limit to the control of the crystal grain size of a magnetic film constituting the above magnetic disk medium, and fine grains and coarse ones coexisted in the magnetic film. Such magnetic films were affected by a leakage magnetic field from surrounding magnetic grains in information recording and, inversely, coarse magnetic grains gave interactions, with the result that stable signal regeneration was sometimes impossible in high-density recording with a recording density exceeding 20 Gb/inch
2
.
The technology described in the above JP-A-60-28637 relates to a perpendicular magnetic recording medium and it was necessary to adjust saturation magnetization to not more than 8.5×10
−2
T (850 gauss) which is a practical range. Saturation magnetization of not more than 8.5×10
−2
T (850 gauss) was too small and this perpendicular magnetic recording medium was inappropriate for a material composition for longitudinal magnetic recording.
Further, the present inventors have found out that making the distribution of magnetic grain size uniform, along with making magnetic grains fine in size, is important for a reduction in thermal fluctuations.
Therefore, the first object of the invention is to provide a low-noise, high-performance magnetic recording medium by making magnetic grains fine in size through the optimization of the composition of a magnetic film.
The second object of the invention is to provide a magnetic recording medium of low thermal demagnetization by controlling the distribution of the magnetic grain size in a small range.
The third object of the invention is to provide a large-capacity magnetic storage system capable of high-density recording with a recording density exceeding 20 Gb/inch
2
.
In the magnetic recording medium having a recording film formed of at least one magnetic layer formed on a substrate via an underlayer, the above first object is achieved when the above at least one magnetic layer is formed of an alloy containing cobalt as the main constituent thereof, chromium and germanium as the additives of the alloy and containing boron or phosphorus as the third additive of the alloy. The above first object is more readily achieved by use of layered structure having at least two underlayers as the above underlayer. Furthermore, when the residual magnetic flux density of the above recording film measured while applying a magnetic field in the relative traveling direction of a magnetic head during recording to the recording medium is expressed as Br while the thickness of the above recording film is expressed as “t”, it is preferred that the value of the product Br×t be not less than 1.6 mA but not more than 5 mA. Here, in a case where the recording film is formed of a plurality of magnetic layers, “t” is the total of the thicknesses of all magnetic layers constituting the recording film. Further, in a case where the magnetic recording medium is a magnetic disk medium used in a magnetic disk device, the above expression “relative traveling direction of a magnetic head during recording to the recording medium” means the circumferential direction of the magnetic disk.
Further, it is preferred that, when the third additive is boron, the contents of the boron and germanium both contained in the above at least one magnetic layer be not less than 1 but not more than 14 atomic % and not less than 5 but not more than 22 atomic %, respectively. In this case it is preferred that the content of
Hosoe Yuzuru
Suzuki Hiroyuki
Tanahashi Kiwamu
Kenyon & Kenyon
Klimowicz William
Watko Julie Anne
LandOfFree
Magnetic recording medium and magnetic storage system using... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic recording medium and magnetic storage system using..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic recording medium and magnetic storage system using... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3127695