Magnetic recording and reading device Number:7,177,115 from the United States Patent and Trademark Office (PTO) owispatent A magnetic recording and reading device having a transfer rate of not less than 50 MB/s includes a magnetic recording medium having an absolute value of normalized noise coefficient per recording density of not more than 2.5.times.10.sup.-8 (.mu.Vrms)(inch) (.mu.m).sup.0.5/(.mu.Vpp), and magnetic head which is mounted on an integrated circuit suspension so that a total inductance is reduced to be not more than 65nH and having a magnetic core which is not more than 35 .mu.m of length, wherein a part of the magnetic core being formed by a magnetic film having a resistivity exceeding at least 50 .mu..OMEGA.cm or by a multilayer film consisting of a magnetic film and an insulating film. The device also includes a fast R/W-IC having a line width of not more than 0.35 .mu.m which is installed in a position within 2 cm from a rear end of the magnetic head.<H recording, Magnetic, Magnetic, record, 7177115.html, Patent, pto, 7177115

Title: Magnetic recording and reading device

Abstract: A magnetic recording and reading device having a transfer rate of not less than 50 MB/s includes a magnetic recording medium having an absolute value of normalized noise coefficient per recording density of not more than 2.5.times.10.sup.-8 (.mu.Vrms)(inch) (.mu.m).sup.0.5/(.mu.Vpp), and magnetic head which is mounted on an integrated circuit suspension so that a total inductance is reduced to be not more than 65nH and having a magnetic core which is not more than 35 .mu.m of length, wherein a part of the magnetic core being formed by a magnetic film having a resistivity exceeding at least 50 .mu..OMEGA.cm or by a multilayer film consisting of a magnetic film and an insulating film. The device also includes a fast R/W-IC having a line width of not more than 0.35 .mu.m which is installed in a position within 2 cm from a rear end of the magnetic head.

Patent Number: 7,177,115 Issued on 02/13/2007 to Shiroishi

Inventors: Shiroishi; Yoshihiro (Hachioji, JP)
Assignee: Hitachi Global Storage Technologies Japan, Ltd. (Odawara, JP)

Appl. No.: 10/644,824

Filed: August 21, 2003

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10115917	Apr., 2002	6819531
09725317	Nov., 2000	6407892
09377189	Aug., 1999	6266210

Foreign Application Priority Data


Aug 20, 1998 [JP]			10-233827

Current U.S. Class: 360/97.01

Current International Class: G11B 5/00 (20060101)

Field of Search: 360/317,126,245.9,67,73.03,77.03,97.01 428/65.3,332,694B,141,822 216/38 430/316 369/13.02

References Cited [Referenced By]

U.S. Patent Documents


4651248	March 1987	Shiiki et al.
4809232	February 1989	Baumbaugh et al.
4949039	August 1990	Grunberg
5143794	September 1992	Suzuki et al.
5206590	April 1993	Dieney et al.
5363251	November 1994	Kamo et al.
5446307	August 1995	Lux et al.
5493467	February 1996	Cain et al.
5494722	February 1996	Oka et al.
5563752	October 1996	Komuro et al.
5572490	November 1996	Kazama
5621596	April 1997	Santini
5712747	January 1998	Voldman et al.
5739988	April 1998	Gill
5761166	June 1998	Sedlmayr et al.
5773199	June 1998	Linliu et al.
5932343	August 1999	Hayashi et al.
5949623	September 1999	Lin
5956208	September 1999	Kawazoe
5969523	October 1999	Chung et al.
5970602	October 1999	Harada et al.
5995329	November 1999	Shiraishi et al.
6002555	December 1999	Tagawa
6014289	January 2000	Goss
6024886	February 2000	Han et al.
6034851	March 2000	Zarouri et al.
6038102	March 2000	Balakrishnan et al.
6043959	March 2000	Crue et al.
6043960	March 2000	Chang et al.
6046882	April 2000	Pattanaik et al.
6055131	April 2000	Takahashi et al.
6069774	May 2000	Arisaka et al.
6090480	July 2000	Hayashi
6114850	September 2000	Hayashi
6122818	September 2000	Lee
6125019	September 2000	Hoshiya et al.
6134084	October 2000	Ohwe et al.
6141190	October 2000	Nakamoto et al.
6163443	December 2000	Hatagami et al.
6178144	January 2001	Huber
6180208	January 2001	Shiratori et al.
6181514	January 2001	Santini et al.
6188546	February 2001	Nakajima et al.
6191911	February 2001	Cai et al.
6194896	February 2001	Takahashi et al.
6201667	March 2001	Yamamoto et al.
6203934	March 2001	Naoe et al.
6215609	April 2001	Yamashita et al.
6266216	July 2001	Hikami et al.
6313969	November 2001	Hattori et al.
6324035	November 2001	Shiroishi
6407892	June 2002	Shiroishi
6410133	June 2002	Kirino et al.
6417998	July 2002	Crue et al.
6423430	July 2002	Hong et al.

Foreign Patent Documents


0 797 187	Sep., 1997	EP
61-97906	May., 1986	JP
63-148411	Jun., 1988	JP
63-234407	Sep., 1988	JP
2-61572	Mar., 1990	JP
2-148643	Jun., 1990	JP
2-218904	Aug., 1990	JP
3-16013	Jan., 1991	JP
4-358310	Dec., 1992	JP
6-20258	Jan., 1994	JP
6-274827	Sep., 1994	JP
7-134820	May., 1995	JP
7-296304	Nov., 1995	JP
7-333015	Dec., 1995	JP
8-153309	Jun., 1996	JP
9-69440	Mar., 1997	JP
9-091660	Apr., 1997	JP
10-143820	May., 1998	JP

Primary Examiner: Chen; Tianjie
Attorney, Agent or Firm: Antonelli, Terry, Stout and Kraus, LLP.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 10/115,917, filed Apr. 5, 2002, now U.S. Pat. No. 6,819,531, which is a continuation of U.S. application Ser. No. 09/725,317, filed Nov. 29, 2000, now U.S. Pat. No. 6,407,892, which is a continuation of U.S. application Ser. No. 09/377,189, filed Aug. 19, 1999, now U.S. Pat. No. 6,266,210, the subject matter of which is incorporated by reference herein, and is related to U.S. application Ser. No. 09/725,253, filed Nov. 29, 2000, now U.S. Pat. No. 6,404,605, which is a continuation of U.S. application Ser. No. 09/377,189, now U.S. Pat. No. 6,266,210, and is related to U.S. application Ser. No. 09/836,481, filed Apr. 18, 2001, now U.S. Pat. No. 6,324,035.

Claims

What is claimed is:

1. A magnetic recording and reading device having a data transfer rate of more than 50 MB/s and a recording density of more than 5 Gb/in.sup.2, which comprises: a magnetic recording medium having a substrate and at least one magnetic recording layer formed above the substrate; a magnetic head enabling the data transfer rate of more than 50 MB/s and the recording density of more than 5 Gb/in.sup.2 on the magnetic recording medium, the magnetic head comprising a recording head having a magnetic core with a magnetic core length l.sub.1 of not more than 35 .mu.m and having a resistivity of more than 50 .mu..OMEGA.cm, and a reading head provided with a read element having a track width of not more than 0.9 .mu.m; and a R/W-IC; wherein the at least one magnetic recording layer contains (1) at least one metal element selected from a first group consisting of Co, Fe and Ni as a primary component, (2) at least two elements selected from a second group consisting of Cr, Mo, W, V. Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, and (3) at least one element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B, said at least one element selected from the third group being in an amount of 0.1 to 15 atomic %.

2. A magnetic recording and reading device according to claim 1, wherein the R/W-IC has a line width of not more than 0.35 .mu.m.

3. A magnetic recording and reading device according to claim 1, wherein the at least one magnetic recording layer contains amorphous material.

4. A magnetic recording and reading device according to claim 1, wherein the magnetic recording medium further comprises a non-magnetic intermediate layer containing at least one element selected from the group consisting of Ru, Pt, Cr, Mo, W, V, Nb, Ta, Zr, Hf, Ti, Ge, Si, Co, Ni, C and B.

5. A magnetic recording and reading device according to claim 1, wherein the magnetic recording medium has a perpendicular anisotropy magnetic recording layer.

6. A magnetic recording and reading device according to claim 5, wherein the recording head has a magnetic pole length I.sub.2 of not more than 50 .mu.m.

7. A magnetic recording and reading device according to claim 5, wherein the perpendicular anisotropy magnetic recording layer has a granular structure.

8. A magnetic recording and reading device according to claim 1, wherein the magnetic recording medium is a magnetic disk which is rotatable at a speed in a range of more than 10,000 rpm.

9. A magnetic recording and reading device according to claim 1, wherein a magnetic pole of the magnetic core is composed of any one material selected from the group consisting of a NiFe-base alloy and an amorphous alloy, the NiFe-base alloy including 42Ni-57Fe-1Cr, 46Ni-52Fe-2Cr, 43Ni-56Fe-1Mo, 51Ni-47Fe-2S and 54Ni-43Fe-3P, and the amorphous alloy includes CoTaZr and CoNbZr.

10. A magnetic recording and reading device according to claim 1, wherein the at least one magnetic recording layer enables reproduction therefrom.

11. A magnetic recording and reading device comprising: a magnetic recording medium having a substrate and at least one thin magnetic recording layer formed above the substrate; a magnetic head enabling a data transfer rate of more than 50 MB/s, and a recording density of more than 5 Gb/in.sup.2 on the magnetic recording medium, the magnetic head having a recording head and a reading head; and a R/W-IC; wherein the recording head has an upper magnetic core and a lower magnetic core with a magnetic core length I.sub.1 of not more than 35 .mu.m; wherein the reading head has a read element having a track width of not more than 0.9 .mu.m; and wherein the at least one thin magnetic recording layer includes a magnetic crystal grains containing (1) at least one metal element selected from a first group consisting of Co, Fe and Ni as a primary component, (2) at least two elements selected from a second group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, and (3) at least one element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Td, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B, said at least one element selected from the third group being in an amount of 0.1 to 15 atomic %.

12. A magnetic recording and reading device according to claim 11, wherein the I.sub.1 is a length between an air-bearing surface of the magnetic core and a connection which connects the upper magnetic core with the lower magnetic core.

13. A magnetic recording and reading device according to claim 11, wherein the RW-IC has a line width of not more than 0.35 .mu.m.

14. A magnetic recording and reading device according to claim 11, wherein the magnetic recording medium further comprises a non-magnetic intermediate layer containing at least one element selected from the group consisting of Cr, Mo, W, Ta, V, Nb, Ta, Zr, Hf, Ti, Ge, Si, Co, Ni, C and B.

15. A magnetic recording and reading device according to claim 11, wherein the at least one thin magnetic recording layer enables reproduction therefrom.

16. A magnetic recording and reading device comprises: a magnetic recording medium having a substrate and a thin magnetic layer formed above the substrate; a magnetic head having a recording head and a reading head; and a RW-IC; wherein the recording head has an upper magnetic core and a lower magnetic core with a magnetic core length I.sub.1 of not more than 35 .mu.m; wherein the reading head has a read element having a track width of not more than 0.9 .mu.m; wherein an absolute value of normalized noise coefficient per recording density of the magnetic recording medium is not more than 2.5.times.10.sup.-8 (.mu.Vrms)(inch)0.5/(.mu.Vpp); and wherein a data transfer rate of the device is more than 50 MB/s, and a recording density is more than 5 Gb/in.sup.2.

17. A magnetic recording and reading device according to claim 16, wherein the RW-IC has a line width of not more than 0.35 .mu.m.

18. A magnetic recording and reading device according to claim 16, wherein the thin magnetic layer includes magnetic crystal grains.

19. A magnetic recording and reading device according to claim 16, wherein the thin magnetic layer includes amorphous magnetic material.

20. A magnetic recording and reading device according to claim 16, wherein the thin magnetic recording layer is a granular type medium.

21. A magnetic recording and reading device according to claim 16, further comprising a rotary type actuator to position the magnetic head in at least two stages.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a magnetic disc device used in computers, information storage devices and so on, a magnetic storage device used in such information home appliances as digital VTRs, and a magnetic recording, and and, more particularly, to a magnetic recording and reading device suitable for realizing high-speed recording and reading, and for high-density recording.

Semiconductor memories, magnetic memories, etc., are used in the storage or recording devices of information equipment. Semiconductor memories are used in internal primary storage in the light of high-speed accessibility and magnetic memories are used in external secondary storages in the light of a high capacity, low cost and nonvolatile property. Magnetic disk devices, magnetic tapes and magnetic cards are the main current in the magnetic memories. A magnetic recording portion which produces a strong magnetic field is used in order for writing magnetic disks, magnetic tapes or magnetic cards. Further, reading portions based on the magnetoresistance effect or the electromagnetic induction effect are used in reading magnetic information recorded at a high density. In recent years, for reading, the giant magnetoresistance effect and the tunneling magnetoresistive effect have also begun to be examined. These functional portions for recording and reading are both installed in an input-output part which is called a magnetic head.

The basic configuration of a magnetic disk device is shown in FIGS. 10A and 10B. FIG. 10A shows a plan view of the device and FIG. 10B shows a vertical-sectional view of the device. Recording media 101-1 to 101-4 are fixed to a hub 104 to be rotated by a motor 100. In FIG. 10B shows one example which comprises four magnetic disks 101-1 to 101-4 and eight magnetic heads 102-1 to 102-8. However, the magnetic disk device may comprise at least one magnetic disk and at least one magnetic head. The magnetic heads 102-1 to 102-8 move on the rotating recording media. The magnetic heads 102-1 to 102-8 are supported by a rotary actuator 103 via arms 105-1 to 105-8. Suspensions 106-1 to 106-8 have function of the pressing the magnetic heads 102 against the recording media 101-1 to 101-4 under a determined load, respectively. A given electric circuit is needed for processing of reproduction signals and for inputting and outputting of information. Recently, a signal processing circuit in which waveform interference at high-density is positively utilized, such as PRML (Partial Response Maximum Likelihood) or EPRML (Extended PRML) which is an enhanced. PRML, has been adopted, contributing greatly to a high-density design. The signal processing circuit is installed in a circuit board on a cover 108, etc.

The functional portion for writing and reading information on a magnetic head assembly is comprises components shown in FIG. 11A, for example. A writing portion 111 is comprised of a spiral coil 116 between magnetic poles 117, 118 which are magnetically connected with each other. The magnetic poles 117, 118 are both composed of a magnetic film pattern, which are made of an NiFe alloy, etc., respectively. The reading portion 112 comprises a magnetoresistance element 113 made of an NiFe alloy, etc. and an electrode 119 for applying a constant current or a constant voltage to the element 113 and for detecting changes in resistance. The magnetic pole 118, which is made of an NiFe alloy, etc. and serves also as a magnetic shielding layer, is provided between the writing and reading portions. There is further a shielding layer 115 underneath the magnetoresistance element 113. A reading resolution is determined by the clearance distance between the shielding layer 115 and the magnetic pole 118 (serving also as another shielding layer). The functional portion is formed on a magnetic head slider 1110 (FIG. 11B) via an underlayer 114 made of Al.sub.2O.sub.3, etc. Incidentally, the magnetic head slider, which is provided with a protection layer made of hard-carbon, etc. on the surface opposed to the magnetic recording medium, is supported by a gimbal 1111 and a suspension 1113, as shown in FIG. 11B. The magnetic head slider moves relatively to the magnetic recording medium while floating from the medium surface and, after positioning in an arbitrary position by an arm 1114 connected to a motor, realizes the function of writing or reading magnetic information via lead lines 1116 and 1115. With respect to the above function, there is also provided an electric control circuit together with the aforementioned signal processing unit or on the head carriage.

A detailed structure of a recording medium is schematically shown in FIG. 12. As described in JP-A-3-16013, most of the conventionally used recording media are produced by forming a magnetic layer 123 made of a Co--Cr--Ta alloy, or a Co--Cr--Pt alloy, etc. on a non-magnetic substrate made of Al plated with an NiP alloy, a glass, a high-hardness ceramics, a polished Si or the like, or a plastic substrate 121 by the sputtering method, or the evaporation method, or the plating method, etc. Usually, an under layer 122 made of Cr, or a Cr alloy, etc. for orientation control of the magnetic layer is often formed on the substrate. Furthermore, a protection film 124 made of diamond-like carbon containing nitrogen and/or hydrogen, or SiO.sub.2 or SiN or ZrO.sub.2, etc. is provided to ensure durability of sliding resistance, and a lubricating film 125 made of perfluoro alkyl polyether having an adsorptive or a reactive end group, or organic fatty acids, etc. is provided.

In addition to the magnetic recording device, magneto-optic recording devices that perform recording and reading on a magnetic recording medium through the use of light have also been put to practical use. The magneto-optic recording devices are classified into one type in which recording is performed only by light modulation and another type in which recording and reproduction are performed by light with a modulated magnetic field. However, the both types greatly rely on heat when recording and reading. Therefore, according to such type of devices, it is impossible to perform recording and reading in high data transfer rate and thus they have been adopted mainly in backup systems, etc.

The importance of a storage device is determined by its storage capacity and the speed during inputting-outputting operations. In order to increase competitiveness of products, it is necessary for the storage device to increase capacity by higher recording density, higher rotational speed and higher data transfer rate than those of the prior art. Thus, an important problem to be solved by the present invention is to provide a device capable of recording and reading at a high data transfer rate of not less than 50 MB/s and, more preferably, that at a high density of not less than 5 Gb/in.sup.2. A magnetic recording medium capable of recording and reading at a high frequency and capable of obtaining a high S/N ratio at a high density and a magnetic head capable of generating a sufficient magnetic recording field at a high frequency are necessary for meeting the requirement.

In conventional magnetic recording media, there have been proposed and actually carried out to reduce noise by refining crystal grains in order to obtain a high S/N ratio at a high density of about 1 to 3 Gb/in.sup.2, and by promoting segregation of non-magnetic components at grain boundaries to reduce exchange coupling among crystal grains as being taught in JP-A-63-148411, JP-A-3-16013 and JP-A-63-234407 so as to make the coercive squareness S* to not more than 0.85 and the rotational hysteresis loss RH to the range of 0.4 to 1.3. Noise can be considerably reduced by recording and reading at a data transfer rate of not more than about 20 MB/s. However, when the magnetic recording was carried out on that film media of the prior art at a high frequency of not less than 50 MB/s, thermal fluctuation effects in fine magnetic crystallines is remarkable due to weak exchange coupling among crystal grains and the apparent coercive force is high resulting in that it was impossible to record on it accurately. Furthermore, even when recording is performed under a large current with utilization of a modified recording circuit, etc., the magnetic recording transition region is widened due to a broad magnetic recording field resulting in that noise increases and/or recorded information is lost when it was alowed to stand for a long time.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a low-noise magnetic recording medium composed of fine crystal grains which is capable of recording and reading at a high data transfer rate of not less than 50 MB/s and further permits high-density recording at not less than about 5 Gb/in.sup.2, a recording and reading magnetic head with high reading sensitivity which is capable of sufficiently sharp recording on the medium, and a magnetic recording device of a high data transfer rate and high density which is realized by using the magnetic recording medium and the magnetic head of the present invention.

In order to achieve the above object, the present inventors pushed forward studies on chemical compositions of magnetic recording media, deposition processes and technologies related to devices such as magnetic heads, and found out that the following means are very effective.

There is proposed a magnetic recording medium with a magnetic layer comprising at least one metal element selected from the group consisting of Co, Fe and Ni as a primary component, at least two elements selected from a second group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, and at least one element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B. According to the magnetic recording medium, it is possible to obtain a high S/N (signal-to-noise) ratio even under recording at high data transfer rate of not less than 50 MB/s and to reduce the absolute value of normalized noise coefficient per a unit transition {square root over (Nd.sup.2-No.sup.2)} {square root over (Tw)}/(S.sub.0D)(Nd: recorded media noise, No: DC erase noise, Tw: effective read track width, S.sub.0: isolated pulse output, D: recording density in the unit of flux change per inch) to not more than 2.5.times.10.sup.-8 (.mu.Vrms) (inch)(.mu.m).sup.0.5/(.mu.Vpp)

The invention can provide a magnetic recording device which can perform recording at a high data transfer rate of not less than 50 MB/s by using the above magnetic recording medium, a magnetic recording head and an R/W-IC having the following features; that is, the magnetic recording head assembly is given a total inductance reduced to not more than 65 nH because it has a magnetic core length of not more than 35 .mu.m, because it is provided with a magnetic film with a resistivity exceeding 50 .mu..OMEGA.cm or a multilayer film composed of a magnetic film and an insulating film in part of the magnetic core, and further because it is mounted on an integrated circuit suspension; and the R/W-IC produced using a process of a line width of not more than 0.35 .mu.m and is capable of operating at high frequencies. Furthermore, the magnetic recording device of the present invention can perform the reading of magnetic information at a high density of not less than 5 Gb/in.sup.2 by using a magnetic head provided with a read element having a giant magnetoresistance effect or a tunneling-magnetoresistance effect and with an effective track width of not more than 0.9 .mu.m.

Recording density can be increased about 20% by forming the magnetic layer of the magnetic recording medium through a non-magnetic intermediate layer comprising at least one element selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Zr, Hf, Ti, Ge, Si, Co, Ni, C and B as a primary component

A magnetic recording and reading device of higher density can be provided by performing magnetic recording immediately after heat application to a magnetic recording medium through the use of a semiconductor laser, etc. and performing reading with the aid of the above giant magnetoresistance effect element or an element having a tunneling-magnetoresistive thin film.

Furthermore, in order to shorten an access time and perform positioning with higher accuracy, it is effective to adopt a rotary type actuator to position the head in at least two stages of coarse and fine movement adjustments.

The present inventors pushed forward on read-and-write properties of a magnetic recording medium as shown in FIG. 12, which is fabricated by forming a magnetic layer of a Co alloy, etc., a protective layer of C--N, etc., and a lubricating layer of perfluoro-alkyl-polyether, etc., in this order, directly on a non-magnetic substrate or via a non-magnetic underlayer which comprises at least one element selected from the group consisting of Cr, Mo, W, Ta, V, Nb, Ta, Ti, Ge, Si, Co and Ni as a primary component, the above magnetic layer was formed by controlling film deposition conditions, such as substrate temperature, atmosphere and deposition rate, heat treatment conditions, compositions of magnetic layer or under layer, a thickness of each layer, crystalline, the number Cf layers, etc. At a recording density of 3 Gb/in.sup.2 and at 10 kprm, these magnetic media were evaluated through the use of a conventional magnetic head with the MR element as shown in FIGS. 11A and 11B on a conventional magnetic disk device as shown in FIGS. 10A and 10B. As a result, the present inventors found out that by giving the above magnetic layer of a composition containing at least one metal element selected from the group consisting of Co, Fe and Ni as a primary component, and at least two elements selected from a second group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, it is possible to refine crystal grains and reduce the exchange interaction among crystal grains and also to reduce the absolute value of normalized noise coefficient per recording density to not more than 3'10.sup.-8 (.mu.Vrms) (inch) (.mu.m).sup.0.5/(.mu.Vpp) even when recording and reading are performed at a transfer rate of not more than 20 MB/s of conventional technology. This effect was remarkable especially during low-pressure, high-temperature and high.sub.irate film depositions or during film depositions at a high pressure and a low deposition rate. Under other conditions, however, this effect was good enough by optimizing compositions and combinations.

On the other hand, in order to record at a high rate of not less than 50 MB/s, it was necessary to use an R/W-IC (Read and Write IC) which is capable of a high speed processing by putting fine-pattern-width for not more than 0.35 .mu.m to partial use at least and, in addition, it was necessary to develop a magnetic recording head structure capable of generating a strong magnetic recording field at a high rate in response to this fast driving current. In order to prevent the deterioration of fast signals, it is important that the IC be installed in a position as close to the head as possible and it was desirable to reduce the distance to not more than 2 cm. The present inventors examined magnetic pole and head structures and materials for magnetic poles, and developed a magnetic head assembly with a total inductance reduced to not more than 65 nH in which the magnetic core length l.sub.1 of a magnetic recording core composed of the lower magnetic pole 118 and the upper magnetic pole 117 in FIG. 11A is not more than 35 .mu.m, and which is provided with a magnetic film with a resistivity exceeding 50 .mu..OMEGA.cm or a multilayer film composed of a magnetic film and an insulating film in part of the magnetic poles composing the magnetic core, and which is mounted on a suspension 113 with an integrated conductive line through insulator 1116. Recording magnetic fields obtained by this magnetic head were evaluated with the aid of a magnetic field SEM, MFM, etc. As a result, the present inventors could ascertain that a sufficient magnetic field can be generated even at a data transfer rate of not less than 50 MB/s, and found out that recording at a transfer rate of not less than 50 MB/s is, in principle, possible. Materials for magnetic poles with a resistivity exceeding 50 .mu..OMEGA.cm include, for example, NiFe-base alloys, such as 42Ni-57Fe-1Cr, 46Ni-52Fe-2Cr, 43Ni-56Fe-1Mo, 51Ni-47Fe-2S and 54Ni-43Fe-3P, and amorphous magnetic alloys, such as CoTaZr and CoNbZr. Examples of multilayer film composed of a magnetic film and an insulating film include a multilayer film composed of 89Fe-8Al-3Si and SiO.sub.2 and a multilayer film composed of 80Ni-20Fe and ZrO.sub.2.

When recording and reading on the above medium at 50 MB/s through the use of the magnetic head and circuit of the above construction, satisfactory recording was incapable due to a bad overwrite characteristic, etc. and besides noise increased twice or three times. Thus, it became apparent that further ideas are necessary for ensuring recording and reading both in high-density and high data transfer rate. Here, signals were read through the use of a conventional MR read element with a narrow track width of 2 .mu.m.

The reason for the above phenomenon was examined. The present inventors considered that the above phenomenon is due to a bad frequency response in the recording characteristic of the medium. Therefore, the cause was analyzed by performing a simulation through the use of a super computer, etc. and as a result, it became evident that there is a problem in thermal fluctuations of magnetization and spin damping during recording process. Therefore, studies were carried out on medium additives capable of optimizing thermal fluctuations and damping coefficient. As a result, the present inventors found out that by adding at least one element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B to the composition of the above medium, it is possible to reduce the absolute value of normalized noise coefficient per recording density to not more than 2.5.times.10.sup.-8(.mu.Vrms) (inch) (.mu.m).sup.0.5/(.mu.Vpp) even when recording is performed at 50 MB/s. This effect was observed when the above elements were added in amounts of not less than 0.1 at %. However, their addition in an amount of 1 at % is sufficient. Addition in amounts of not more than 15 at % was undesirable because of a remarkable decrease in output. Furthermore, the effect was remarkable when rare earth elements were added. The above effect was also ascertained in what is called a granular type medium in which a non-magnetic substance, such as SiO.sub.2 and ZrO.sub.2, and a magnetic material with a high crystalline anisotropy constant, such as CoPt and CoNiPt, were simultaneously formed by sputtering and the magnetic material with a high crystalline anisotropy constant was precipitated and dispersed by heat treatment at a temperature of about 300.degree. C. to obtain the above composition. Furthermore, in a case where the above magnetic layer is made of an amorphous magnetic substance, the magnetic layer often has perpendicular anisotropy. However, the same effect was also observed in this case. Furthermore, in any of these instances, when the above magnetic layer was formed via a non-magnetic intermediate layer containing at least one element selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Zr, Hf, Ti, Ge, Si, Go, Ni, C and B as a primary component, noise could be remarkably reduced because of statistical addition of signals and this was especially favorable for noise reduction. Furthermore, what is especially noteworthy is that by reducing the magnetic core length of the above magnetic head to not more than 50 .mu.m, a sharp and strong magnetic field could be generated with increased efficiency and recording on a medium with a higher coercive force was possible. This is preferable because higher densities can be obtained. Furthermore, by installing the above R/W-IC near the suspension, the rise time of a recording magnetic field could be made further shorter. This permitted sharp recording and enabled medium noise to be relatively reduced. Therefore, this is more preferable.

In order to perform recording and reading at a high density of not less than 5 Gb/in.sup.2, it was necessary to perform the reading of magnetic information through the use of a magnetic head having an effective read-track width of not more than 0.9 .mu.m with giant magnetoresistive effect or tunneling-magnetoresistive effect, and performs the reading of magnetic information at a high density of not less than 5 Gb/in.sup.2. By performing reading like this, a signal-to-noise ratio of not less than 20 dB of the device necessary for the operation of the device was obtained with the aid of the signal processing method and it was necessary to combine the magnetic head with signal processing such as EPRML or EEPRML, trellis coding, ECCs, etc. Incidentally, the giant magnetoresistive element (GMR) and tunneling magnetic head technologies are disclosed in JP-A-61-097906, JP-A-02-61572, JP-A-04-35831, JP-A-07-333015, JP-A-02-148643 and JP-A-02-218904. An effective track width of not more than 0.9 .mu.m was realized by putting lithography technology based on an i-line stepper or a KrF stepper, FIB fabrication technology, etc. to full use.

The above system was a very epoch-making product as a magnetic disk. However, the present inventors found out that recording can be assisted by instantaneously heating a medium to the temperature range of from about 50.degree. C. to 250.degree. C. with a magnetic disk provided with a heat-generating portion and thereby reducing the coercive force at a high frequency, and that this idea is further effective. In other words, in this system the load put on the recording portion and the material for recording magnetic poles could be reduced, and recording at a high density of not less than 5 Gb/in.sup.2 and a high data transfer rate of not less than 50 MB/s was possible even with a recording track width of not more than 0.9 .mu.m and even when a magnetic pole material with a saturation magnetic flux density of 1 T was used. Thus, this was especially advantageous.

With respect to this effect, access time can also be shortened by performing magnetic recording immediately after heat application to a magnetic recording medium and performing reading with the aid of the above giant magnetoresistive element or element having a tunneling-magnetoresistive effect. This is further preferable.

Furthermore, by using a semiconductor laser chip as the above heat-generating portion, an effective head volume can be reduced and high-speed positioning becomes possible. This is especially preferable. In addition, in order to shorten access time and ensure positioning with a higher accuracy, it is especially effective to position the head by a rotary actuator method in at least two stages of coarse and fine movement adjustments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically the essential portion of a magnetic recording medium of the invention;

FIG. 2 shows schematically the essential portion of a magnetic head assembly of the invention;

FIG. 3A shows schematically a plan view of a magnetic recording device of the invention;

FIG. 3B shows a cross-sectional view of the magnetic recording device shown in FIG. 3A;

FIG. 4 shows schematically the essential portion of another magnetic head assembly of the invention;

FIG. 5A shows schematically the essential portion of a magnetic head of the invention;

FIG. 5B shows schematically the essential portion of another magnetic head of the invention;

FIG. 6A shows schematically the essential portion of magnetic write head pole structure of the invention;

FIG. 6B shows a cross-sectional view of the magnetic head pole structure shown in FIG. 6A;

FIG. 7A shows schematically the essential portion of another magnetic write head pole structure of the invention;

FIG. 7B shows a cross-sectional view of the magnetic write head pole structure shown in FIG. 7A;

FIG. 8A shows schematically the essential portion of still another magnetic write head pole structure of the invention;

FIG. 8B shows a cross-sectional view of the magnetic write head pole structure shown in FIG. 8A;

FIG. 9 is a graph showing an effect of additive elements;

FIG. 10A shows schematically a plan view of a conventional magnetic disk device;

FIG. 10B shows a sectional view of the conventional magnetic disk device shown in FIG. 10A;

FIG. 11A shows schematically a partial sectional view of the essential portion of a conventional magnetic head with write and read elements;

FIG. 11B shows schematically the conventional magnetic head shown in FIG. 11A; and

FIG. 12 shows schematically the essential portion of a conventional magnetic recording medium.

EXAMPLE 1

The magnetic disk of the invention is shown in FIGS. 3A and 3B. FIG. 3A is a plan view of the device and FIG. 3B is a sectional view of the device. In the device of the invention, a recording medium 31 of the invention, which will be described later in detail by referring to FIG. 1, is fixed to a rotary hub 34 and rotated by a motor 310, and recording is performed by a magnetic head 32, which will be described later in detail by referring to FIGS. 11A and 11B. The magnetic head 32 is supported by a rotary actuator 33 via an arm 311 and positioned fast and in a stable manner in a prescribed position of the rotating recording medium 31. In the drawing, the numeral 313 denotes a suspension and numeral 20 denotes a gimbal. As shown in FIG. 2 which illustrates the details of the suspension 313, the suspension 313 used in this device is an integrated circuit suspension in which the wiring 21 and an insulating layer are integrally formed on a plate spring through the use of the thin film technology so that the inductance of the wiring 21 is not more than 15 nH. Lead lines 25 are connected to the wiring 21. Usual wiring of twist wires and wiring with an inductance of not less than 15 nH, signals higher than 50 MB/s attenuate greatly. Thus, conventional types of wiring could not been adequately put to practical use when circuits of usual power were used. In a case where an R/W-IC portion 314 was formed on the above integrated circuit suspension 313, in which the thin-film wiring and insulating layer were directly formed on the plate spring, or an FPC for wiring, and the distance from the head was not more than 2 cm, the attenuation of signals was not practically observed and an improvement in transfer rate of not less than tens of megabytes per second was observed compared to a case where an R/W-IC was integrated with a signal processing circuit and mounted on a circuit board as conventionally. Thus, this was especially preferable. In this example of the invention, the distance was set at 1.5 and 1 cm. Incidentally, FIGS. 10A and 10B illustrates an example in which four magnetic disks 31-1 to 31-4 and eight magnetic heads 32 are mounted. However, at least one magnetic disk and at least one magnetic head may be installed. In this example of the present invention, 1 to 30 heads and 1 to 15 magnetic disks were mounted on a casing 312 of magnetic disk device shown in FIG. 3.

The same prescribed electric circuit as conventional technology is required for recording information, processing read signals and inputting/outputting information. In terms of power consumption, however, a circuit using a CMOS is advantageous in comparison with a circuit using a Bi-CMOS and it is necessary to downsize circuitry in order to perform recording and reading at a high rate of 50 MB/s. In all cases, therefore, it was necessary to adopt the patterning process for not more than 0.35 .mu.m in fabricating a part of the R/W-IC. In an actual case where a patterning process for not less than 0.5 .mu.m was adopted, good recording could not be performed. Incidentally, for channel LSIs for signal processing, etc., it is necessary to reduce the circuit scale in order to reduce power consumption and a patterning process for not more than 0.25 .mu.m was adopted. In this example, a signal processing circuit in which waveform interference in the age of high-density design is positively utilized was introduced and separated from the above R/W-IC. This signal processing circuit is called MEEPRML (Modified EEPRML), in which EEPRML (Extended Extended Partial Response Maximum Likelihood) is enhanced and the ECC function is also enhanced. Furthermore, in the case of perpendicular magnetic recording, reading was performed by the PR5 signal processing method, etc. These components were installed in the circuit board on the cover 312, etc. The number of revolutions of the device was 10,000 rpm and the flying height was from 26 to 28 nm in all cases.

The medium and magnetic head of the present invention, which compose the magnetic recording and reading device of the present invention, is explained below in further detail.

First, the medium of the present invention is explained by referring to FIG. 1. The numeral 11 indicates a non-magnetic substrate which is made of glass, NiP-plated Al, ceramics, Si, plastics, etc. and formed on a disk with a diameter of, for example, 3.5'', 2.5'', 1.8'' and 1'', a tape or a card. The numeral 12 indicates a non-magnetic underlayer which is made of Cr, Mo, W, CrMo, CrTi, CrCo, NiCr, CoCr, Ta, TiCr, C, Ge, TiNb, etc. and contains at least one kind of element selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Ge, Si, Co and Ni as a primary component. The numeral 13 indicates a hard magnetic layer which comprises a crystalline magnetic substance of CoCrPtLa, CoCrTaCe, CoNiPtPr, CoPtNd--SiO.sub.2, FeNiCoCrPm, CoFePdTaSm, NiTaSiEu, CoWTaGd, CoNbVTb, GdFeCoPtTa, GdTbFeCoZrRh, FeRhSiBi--N, CoPtIrSn--CoO, etc., which crystalline magnetic substance contains at least one metal element selected from the group consisting of Co, Fe and Ni as a primary component, at least two elements selected from a second group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, and a least one kind of element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B. This hard magnetic material has an absolute value of normalized noise coefficient per recording density of not more than 2.5.times.10.sup.-8 (.mu.Vrms)(inch)(.mu.m).sup.0.5/(.mu.Vpp). The numeral 14 indicates a protective layer made of C to which N and H are added in combination, H-added C, BN, ZrNbN, etc. The numeral 15 indicates a lubricant of perfluoro-alkyl-polyether having adsorptive or reactive end-groups such as OH and NH.sub.2, an organic fatty acid, etc. Between the non-magnetic under layer 12 and the hard magnetic layer 13, there may be provided a second non-magnetic underlayer whose composition is further adjusted and which has a lattice constant capable of being more easily matched to that of the magnetic film. When the above magnetic layer is divided by a non-magnetic intermediate layer which contains at least one element selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Zr, Hf, Ti, Ge, Si, Co, Ni, C and B as a primary component, noise decreases almost in proportion to the square root of the total number of magnetic layers. Therefore, this is more preferable.

Embodiments of medium of the present invention are explained below in further detail. The magnetic disks of the present invention shown in Table 1 were obtained by first forming an underlayer on a glass disk substrate with a diameter of 3.5, 2.5, 1.8 or 1 inch, then forming a magnetic layer of single-layer, two-layer or multilayer structure, a 10-nm thick carbon protective film to which 10% N is added, and finally forming a 5-nm thick lubricating film of perfluoro alkyl polyether having--OH end group after surface treatment. The above underlayer is made of the Cr alloys, Mo alloys, Ti alloys, W alloys, etc., which contains at least one element selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Ge, Si, Co and Ni as a primary component. The above magnetic layer comprises a crystalline magnetic material of CoCrPtGd, CoCrPtTaNd, CoPtDy--SiO.sub.2, FeCoNiMoTaBi, NiFeCrPtGe, FeNiTaIrSm, etc., which crystalline magnetic material contains at least one metal element selected from the group consisting of Co, Fe and Ni as a primary component, at least two elements selected from a second group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, Pd, Pt, Rh, Ir and Si, and at least one element selected from a third group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, Sb, Pb, Sn, Ge and B.

The above underlayer and magnetic layer were both formed by means of a DC magnetron sputtering device and the above protective film was formed in an N.sub.2 gas atmosphere by the plasma-induced reactive magnetron sputtering method. Incidentally, in this example, parameters could be varied independently of the underlayer and magnetic film each other and Ar pressures of from 1 to 10 m Torr, substrate temperatures of from 100 to 300.degree. C. and deposition rates of from 0.1 to 1 nm/s were used. In the underlayer, Cr, Ta, Nb, V, Si and Ge or alloys such as Co60Cr40, Mo90-Cr10, Ta90-Cr10, Ni50Cr50, Cr90-V10, Cr90-Ti10, Ti95-Cr5, Ti--Ta15, Ti--Nb15, TiPd20, TiPt15, etc. were used as a single layer or two layers composed of dissimilar metal layers. Thus, samples of different underlayer compositions were prepared. The total film thickness of the underlayer was from 10 to 100 nm, that of the magnetic layer was from 10 to 100 nm, and that of the protective film was 10 nm. A multilayer medium 70 nm in thickness was also made by way of trial by depositing ten layers of a combination of 5-nm thick CoCr.sub.7Pt.sub.6Gd.sub.3 and 2-nm thick Pt layers. The ma