WO2004070710A1

WO2004070710A1 - Magnetic recording medium and magnetic storage apparatus

Info

Publication number: WO2004070710A1
Application number: PCT/JP2003/001264
Authority: WO
Inventors: E. Noel Abarra
Original assignee: Fujitsu Limited
Priority date: 2003-02-06
Filing date: 2003-02-06
Publication date: 2004-08-19
Also published as: AU2003206135A1

Abstract

A magnetic recording medium is providedwith a magnetic layer on a NbRuV alloy underlayer.A buffer layer made of either a bcc Cr alloy or anhcp CoCr alloy is disposed between the magnetic layer and the underlayer to minimize diffusion between the layers. The underlayer preferablycontains less than 50 at.% Nb and less than 40 at.%Ru. The lattice parameter is > 3Å but < 3.2Å, and promotes small grain sizes and good in-planeorientation for the magnetic layer.

Description

DESCRIPTION

MAGNETIC RECORDING MEDIUM AND MAGNETIC STORAGE APPARATUS

TF1CHNTCAT, FIELD

The present invention generally relates to magnetic recording media and magnetic storage apparatuses, and more particularly to a magnetic recording medium having an underlayer and a buffer layer under a magnetic layer, and to a magnetic storage apparatus which uses such a magnetic recording medium.

BACKGROUND ART

A typical longitudinal magnetic recording medium includes a substrate, a seed layer, a Cr or Cr alloy underlayer, a Co alloy magnetic layer where information is written, a C overlayer, and an organic lubricant. Substrates that are being presently used include NiP-plated Al-Mg and glass substrates. Glass substrates have been getting more popular due to their resistance to shock, smoothness, hardness, light weight, and reduced flutter especially at a disk edge in case of a disk-shaped magnetic recording medium.

The icrostructure of the magnetic layer which includes grain size, size distribution, preferred orientation and Cr segregation, strongly affects the recording characteristics of the magnetic recording medium. The microstructure of the magnetic layer has widely been controlled by the use of seed layers and underlayers . Small grain size and size distribution with excellent crystallographic orientation are desired.

Underlayers are crystalline and mostly bcc such as Cr and NiAl , and have either a (002) , (110) , or (112) fiber texture. Seed layers are usually amorphous or at least have amorphous surfaces such as NiP which is electroplated or sputtered on the substrate . Underlayers are subsequently grown and develop a particular crystallographic texture. The heteroepitaxial relationships that lead to Co [ 0002 ] being in the plane are Cr (002) //Co (1120) , Cr (110) //Co(1010) , and Cr (112 ) //Co (1010) . Cr(llO) also results in Co (1011) which is ~ 28° from the plane resulting in poor resolution, that is, high density bits are difficult to realize. Present magnetic recording media are composed of small grains of average size of < 10 nm. The epitaxial relationships occur for each grain with the Co [0002] randomly directed in the plane or in some preferred direction as occur in magnetic recording media based on mechanically textured substrates .

The most extensively used underlayer has been Cr or alloys of Cr such as CrMo, CrMn, CrNb,

CrRe, CrRu, CrV, CrTi and CrW, where typically, the Cr content is at least 70 at . % and the additives are most often for enlarging the lattice parameter. The alloying elements can be mixed, and for example, Mo and W can be added to Cr, but the predominant component is still Cr (> 70 at.%) to take advantage of the Cr property of growing with a (002) texture on various seed layers.

Little investigation has been made on using the above described additives or their alloys without Cr . In most cases, for bcc alloys not mainly made of Cr, a strong (110) texture is developed and not the desired (002) or (112) textures . A notable exception is V-rich VMn which grows with a (002) texture when deposited at high temperatures (> 200°C). The texture is further improved when seed layers such as Ta-N are used. Kataoka et al . , "Magnetic and recording characteristics of Cr-, T , W and Zr pre-coated glass disks", IEEE Trans. Magn., vol.31, pp .2734-2736 , No 1995 reported Cr, Ta , , and Zr "pre-coating" layers on glass. For Ta films, reactive sputtering with a proper amount of N₂ actually improves the succeeding Cr underlayer crystallographic orientation as noted in a United States Patent No.6,174,582 to Bian et al . , but media performance cannot match those on NiP seed layers. Cr directly deposited on glass at high temperatures (> 200°C) develop the preferred (002) orientation, but the undesirable (110) texture also arises .

Cr alloy underlayers are usually grown at Ts > 180 °C on mechanically textured or nontextured Ni₈₁P₁₉ seed layers. Low Ts deposition may result in smaller grains, but a (110) texture is developed. Mechanical texturing invariably exposes NiP to air which oxidizes the film surface. Oxidation is important for the Cr to grow with a (002) texture which results in the subsequently deposited magnetic layer to have a (1120) crystallographic texture (or to use a different notation, [1120] preferred orientation) . This is taken advantage of by in a United States Patent No.5, 866, 227 to Chen et al . in which a reactively sputtered NiP (with 0₂) seed layer on glass substrates is described. NiP does not adhere very well to glass such that an adhesive layer such as described in a United States Patent No.6, 139, 981 to Chuang et al . is usually employed.

Mechanical texturing of the NiP seed layer or of the substrate gives rise to orientation ratio (O.R.) > 1, and the c-axes are anisotropic in the plane with most of them pointing towards the groove (disk circumferential) direction in the case of the disk-shaped magnetic recording medium. An O.R. > 1 results in improvements in media signal-to-noise ratio (SNR) as well as thermal stability. An O.R. > 1 can only occur on underlayers with the (002) texture due to the two possible directions (90° from each other) which Co [0002] can take. The Co (1120) surface is ~4.lA X ~4.3A on each side such that if the tecc lattice is stressed (rhombus-like) , one direction will be preferred over the other.

On NiP seed layers, underlayer grain sizes in the order of .8 nm to 10 nm can be realized by using two Cr alloy layers and by reducing the total underlayer thickness t to less than 10 nm. Increasing the underlayer total thickness t tends to significantly increase the average grain size. For example, for a single layer of Cr₈₀Mo₂₀, at t = 30 nm, the average grain size can be approximately 20 nm which is obviously inadequate for present day media noise requirements. Tang et al . , "Microstructure and texture evolution of Cr thin films with thickness", J. Appl . Phys . , vol.74, p .5025-5032 , Oct. 1993 also observed grain diameter increase with thickness .

To achieve an average grain size less than 8 nm is difficult as further reduction of the underlayer thickness results in magnetic layer c- axis in-plane orientation (IPO) degradation.

Moreover, although the underlayer average grain size can be small, a few large grains occasionally occur on which two or more magnetic grains may grow. The effective magnetic anisotropy of such grains may be reduced if magnetic isolation is not complete. The crystallographic quality of the magnetic layer deposited on such a thin Cr underlayer also suffers as observed in the reduced magnetization of the stabilization layer of synthetic ferrimagnetic media (SFM) . Synthetic ferrimagnetic media (SFM) are proposed in Abarra et al . , "Synthetic Ferrimagnetic Media", IEEE Trans. Magn . , vol.37, pp .1426-1431 , July 2001 .

A United States Patent No.5, 693, 26 to Lee et al . describes ordered intermetallic underlayers with the B2 structure such as NiAl and FeAl . Ordered intermetallic alloys with structures such as B2 and ordered alloys with the L₁₀ and L₁₂ structures are expected to have small grain sizes presumably due to the strong binding between the component atoms. Both NiAl and FeAl grow on glass substrates with a (211) fiber texture. Grain sizes in the order of 12 nm can be achieved even for thick (> 60 nm) layers. However, to achieve smaller grain sizes, the thickness has to be reduced but this results in a weakening of the (211) texture. Achieving grain sizes < 10 nm with NiAl and still maintain excellent IPO is difficult.

For NiAl (211) underlayers on glass and Cr (002) on either NiP or TaN seed layers, the magnetic grain c-axes of the subsequently deposited magnetic layers are largely in the plane. However, the degree of alignment differs. Good IPO leads to an increase in remanent magnetization and signal thermal stability. It also improves resolution or the capacity of the medium to support high density bits. Recently developed SFM provides improved thermal stability and resolution compared to conventional magnetic recording media of the same Mrt (remanent magnetization and thickness product) . Underlayers that can be used for conventional magnetic recording media can also be used for SFM, but the potential of the SFM media for extending the limits of longitudinal recording can best be realized if the IPO is close to perfect.

The IPO can be quantified by low incident angle XRD such as that made by Doerner et al . ,

"Microstructure and Thermal Stability of Advanced Longitudinal Media", IEEE Trans. Mag . , vol.36, pp.43-47, Jan. 2001, and Doerner et al . , "Demonstration of 35 Gbits/in² in media on glass substrates", IEEE Trans. Magn . , vol.37, pp .1052-1058 , March 2001 (10 Gbits/in² and 35 Gbits/in² demo) or more simply by taking the ratio of the coercivity normal to and along the film plane (h = Hc-L/Hc) .

The ratio h for media on Cr ( 002 ) /NiP is typically < 0.2 and h > 0 . 2 is observed only for poorly matched underlayers and magnetic layers (in terms of lattice parameters) . For h < 0.2, the M(H) hysteresis loop perpendicular to the film normal is approximately linear with field and HcJ- is typically < 500 Oe. As mentioned earlier, the NiAl (211) texture is weak and thicknesses > 50 nm are usually needed to reduce the occurrence of magnetic grains, with a (0002) orientation. Previous work on using NiAl directly on glass as an underlayer for conventional magnetic recording media resulted in poor squareness {h > 0.25) and could not match the performance of media on Cr (002) /NiP. This is the case even when seed layers such as NiP and CoCrZr are employed.

XRD measurements by Doerner et al . showed that the magnetic c-axes are spread over an angle of > ±20° compared to < ±5° for media on NiP/Al-Mg substrates. For media on Ta-N, though the Cr(002) and Co (1120) peaks are visible from the XRD data, h > 0.2 and as mentioned above, this media underperforms media on Cr (002) /NiP. Aside from the IPO, another concern in the manu acturing of the SFM is the increase in the number of chambers necessary compared to conventional magnetic recording media especially when bare glass substrates are used. Moreover, as throughput has to be maintained at a high level, the thickness of the deposited film is limited to typically 30 nm for each process chamber. Seed layers or underlayers that need to be thicker will require two chambers . The typical sequential deposition must also be made in a rapid fashion not only for a large yield, but also to prevent the temperature of the high emissivity glass substrate to drop before the magnetic layers are deposited. Else, a heating step is needed which will require a separate process chamber. Low emissivity is preferred and substrate emissivity is decreased by each layer deposited on the substrate such that the first few layers (seed layer + underlayer) cannot be very thi .

If a bias voltage is to be applied as in a CVD C deposition, the total medium thickness needed is usually > 30 nm to provide uniform coverage and reduce C overlayer defects . Cr on NiP provides excellent IPO but at least six process chambers are needed for: (1) heating, (2) adhesive layer, (3) seed layer, (4) oxidation, (5) first Cr underlayer, and (6) Cr alloy second underlayer. Usually, a second stage heating is also employed after oxidation to make sure the underlayers and the magnetic layer are grown at a sufficiently high temperature. Steps (3) and (4) may be combined by reactively sputtering NiP in an Ar + 0₂ atmosphere although surface oxidation seems to give better properties . An underlayer + seed layer structure that does not require steps (2) , (4) and (6) and still provide good microstructure would significantly reduce costs as well as process complexity. Underlayers that grow with the proper crystallographic texture at room temperature may be advantageous in getting rid of the first heating stage, but this heating process is helpful in cleaning the substrate surface of unwanted gases.

DISCLOSURE OF THE INVENTION Accordingly, it is a general object of the present invention to provide a novel and useful magnetic recording medium and magnetic storage apparatus, in which the problems described above are eliminated.

Another and more specific object of the present invention is to provide a magnetic recording medium with a seed layer and an underlayer of small grain sizes and excellent in-plane orientation, which layers require only one or two chambers and are of adequate thickness to sufficiently improve the emissivity of a substrate, by use of a NbRuV or NbV alloy underlayer. The seed layer may also be employed which further improves the IPO, and the seed layer may be made of a NbRuV or NbRu alloy reactively sputtered with N₂ or 0₂. The underlayer grows with a (002) texture on the seed layer which promotes a (1120) crystallographic texture for a magnetic layer structure provided on the underlayer or via a buffer layer.

Another more specific object of the present invention is to provide a magnetic storage apparatus which uses one or a plurality of such magnetic recording media having improved performance, Still another object of the present invention is to provide a magnetic recording medium comprising a substrate, a magnetic layer, a NbRuV alloy underlayer provided on the substrate wherein the lattice parameter is < 3.2A and > 3.0A with a predominant fiber texture of (002), and a buffer layer disposed between the magnetic layer and the underlayer. According to the magnetic recording medium of the present invention, the underlayer results in small grain sizes and promotes good IPO, while the buffer layer prevents diffusion of underlayer atoms into the magnetic layer.

A further object of the present invention is to provide a magnetic recording medium comprising a substrate, a magnetic layer, a Nb_xRu_yV_z underlayer, where x > 10 at.%, y ≥ 10 at.%, and 60 at.% < z < 80 at . % , a seed layer disposed between the substrate and the underlayer, and a Cr alloy bcc buffer layer disposed between the underlayer and the magnetic layer, the seed layer promoting small grain sizes and a (002) fiber texture for the underlayer. According to the magnetic recording medium of the present invention, the underlayer results in small grain sizes and promotes good IPO, while the buffer layer prevents diffusion of underlayer atoms into the magnetic layer.

Another object of the present invention is to provide a magnetic storage apparatus comprising at least one magnetic recording medium, and a head recording information on and reproducing information from the magnetic recording medium, wherein the magnetic recording medium comprises a substrate, a Co alloy magnetic layer, a NbRuV alloy underlayer having a thickness of 10 nm to 60 nm disposed between the substrate and the magnetic layer, where Nb = 10 at.% to 60 at.%, Ru = 0 at . % to 40 at.%, V = 55 at.% to 85 at.%, and a lattice parameter is < 3.2A and > 3.0A with a predominant fiber texture of (002) , and a Cr alloy bcc buffer layer having a thickness of 1 nm to 10 nm disposed between the underlayer and magnetic layer. According to the magnetic storage apparatus of the present invention, the underlayer results in small grain sizes and promotes good IPO, while the buffer layer prevents diffusion of underlayer atoms into the magnetic layer, so that magnetic recording and reproduction of high quality is realized. Still another object of the present invention is to provide a magnetic storage apparatus comprising at least one magnetic recording medium, and a head recording information on and reproducing information from the magnetic recording medium, wherein the magnetic recording medium comprises a substrate, a magnetic layer, a NbRuV-alloy underlayer having a thickness of 3 nm to 20 nm with a predominant (002) fiber texture, a Cr alloy bcc layer, provided on the underlayer, and having a thickness of 2 nm to 10 nm, and a seed layer, disposed between the substrate and the underlayer, and having a thickness of 1 nm to 30 nm. According to the magnetic storage apparatus of the present invention, the underlayer results in small grain sizes and promotes good IPO, while the buffer layer prevents diffusion of underlayer atoms into the magnetic layer, so that magnetic recording and reproduction of high quality is realized.

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view showing an important part of a first embodiment of a magnetic recording medium according to the present invention;

FIG. 2 is a cross sectional view showing an important part of a second embodiment of the magnetic recording medium according to the present invention;

FIG. 3 is a cross sectional view showing an important part of a third embodiment of the magnetic recording medium according to the present invention; FIG. 4 is a diagram showing XRD spectra of magnetic recording media on NbRuV underlayers with and without seed layers; FIGS . 5A through 5D are diagrams showing plots of the perpendicular to the film plane hysteresis loop of magnetic recording media on NbRuV underlayers ; FIG. 6 is a diagram showing plots of the perpendicular to the film plane hysteresis loop of a magnetic recording medium with a Nb₁₂Ru₁₆V₇₂ underlayer directly deposited on a glass substrate;

FIG. 7 is a diagram showing XRD spectra of magnetic recording media on a Nb₄₄Ru₁₇V₃₉ underlayer with and without a Nb₃₁Ru₅₃V₁₆-N seed layer;

FIGS. 8A through 8C are diagrams respectively showing plots of the perpendicular to the film plane hysteresis loop of magnetic recording media with a 20 n -thick Nb₄₄Ru₁₇V₃₉ underlayer without a Nb₃₁Ru₅₃V_ls-N seed layer, with the Nb₃₁Ru₅₃V₁₅-N seed layer, and with a 10 nm-thick Nb₄₄Ru₁₇V₃₉ underlayer and a Nb₃₁Ru₅₃V₁₆-N seed layer;

FIG. 9 is a diagram showing an XRD spectra of magnetic recording media on NbV alloy underlayers on glass;

FIGS. 10A through 10C are diagrams respectively showing plots of the perpendicular to the film plane hysteresis loop of the magnetic recording media in FIG. 9 with a Nb₆₅V₃₅ underlayer, with a Nb₄₅V_5s underlayer , and with a Nb₂₆V₇₄ underlayer directly deposited on glass;

FIGS. 11A and 11B are diagrams respectively showing plots of the perpendicular to the film plane hysteresis loop of magnetic recording media with a Nb₁₇V₈₃ underlayer directly on glass and on oxidized NiP;

FIG. 12 is a diagram showing an XRD spectra of magnetic recording media on NbRuV with and without CrTi seed layers;

FIGS. 13A through 13C are diagrams respectively showing plots of the perpendicular to the film plane hysteresis loop of the magnetic recording medium media in FIG. 12 on NbRuV underlayers ;

FIG. 14 is a cross sectional view showing the internal structure of an important part of an embodiment of a magnetic storage apparatus according to the present invention; and

FIG. 15 is a plan view showing the important part of the embodiment of the magnetic storage apparatus shown in FIG. 14.

BEST MODE OF CARRYING OUT THE INVENTION

FIG. 1 is a cross sectional view showing an important part of a first embodiment of a magnetic recording medium according to the present invention. In this first embodiment of the magnetic recording medium, the present invention is applied to a longitudinal magnetic recording medium such as a magnetic disk. The magnetic recording medium shown in FIG,

I includes a substrate 10, a seed layer 11, an underlayer 12, a buffer layer 13, a magnetic layer 14, a C overlayer 15, and an organic lubricant layer 16. The substrate 10 is made of glass. An amorphous layer of NiP may be formed on the surface of the substrate 10 as indicated by 10A in FIG. 1, and in this case, the NiP layer 10A may be oxidized. Of course, it is possible to use an Al substrate having the surface thereof electroplated with NiP as the substrate 10.

The seed layer 11 is made of an amorphous or crystalline material to enhance (002) fiber texture and improve uniformity by masking defects that may exist on the substrate 10. The seed layer

II may be reactively sputtered with either N₂ or 0₂ gas . The seed layer 11 may be made of a NbRuV alloy wherein Nb = 20 at.% to 60 at.%, Ru = 5 at.% to 50 at.%, and V = 10 at.% to 40 at.% with a thickness of 1 nm to 30 nm, with N₂ or 0₂ partial pressure P ≥ 6%. The seed layer alloy is preferably Nb₃₀Ru₄₅V₂₅, Nb₄₀Ru₄₅V_lS, Nb₄₅Ru_3SV₂₀, Nb₅₅Ru₂₅V₂₀, or Nb₅₅Ru₁₀V₃₅.

The seed layer 11 may also be selected from a group consisting of Ni₂P , Ni₃P, Ni₈₁P₁₉ , alloys of CrMoP , CrNiP and NbNiP, wherein the seed layer 11 is surface oxidized by exposure to 0₂ gas after deposition or reactively sputtered in an Ar + 0₂ gas mixture .

In the case of the seed layer 11 made of a crystalline material, the seed layer 11 has a (002) crystallographic texture and a thickness of 10 nm to 30 nm. Hence, it is possible to control the lattice parameter using NbRuV without relying on Cr-M alloys (M = Mo , Ti, Nb, etc.) which tend to increase in grain size with thickness on a crystalline template.

The seed layer 11 may be textured. On the other hand, the seed layer 11 may be omitted.

The underlayer 12 may be made of a NbRuV alloy wherein the lattice parameter is < 3.2A and > 3. OA with a predominant fiber texture of (002) , Nb = 10 at.% to 50 at.%, Ru = 5 at.% to 40 at.%, and V = 55 at.% to 85 at.% with a thickness of 10 nm to 60 nm. The underlayer alloy is preferably Nb₁₀Ru₁₅V₇₅ , Nb₁₅Ru₁₅V₇₀, Nb₃₀Ru₁₀V₆₀, or Nb₄₅Ru₁₅V₄₀. The NbRuV alloy underlayer 12 results in small grain sizes and promotes good IPO.

The underlayer 12 may be made of 10 at.% to 40 at.% Nb and the rest V with a thickness of 10 nm to 60 nm. The buffer layer 13 prevents diffusion of underlayer atoms into the magnetic layer 14. The buffer layer 13 may be made of a Cr-M layer with a thickness of 1 nm to 10 nm, where M is a material selected from a group consisting of Mo, Nb , Ru , Ti,

V, and W of atomic proportion ≥ 10% and < 30%. Cr- rich alloys adhere well to many types of materials such that it makes a good buffer layer between the underlayer 12 and the magnetic layer 14. Hence, the buffer layer 13 prevents the diffusion of the underlayer materials into the magnetic layer 14. Since the Cr lattice parameter (a = 0.2886 nm) is smaller than the NbRuV underlayer lattice parameter (a ≥ 0.30 nm) , it is advantageous to alloy Cr with a larger element such as those listed.

The buffer layer 13 may also be made of a magnetic or nonmagnetic hep-structured CoCr-based alloy film with a thickness of 1 nm to 5 nm, in direct contact with the magnetic layer 14 on top thereof. When hep magnetic CoCr-based alloys are grown directly on bcc films, a portion of the magnetic layer in contact with the bcc underlayer is adversely affected due to lattice mismatch and/or Cr or NbRuV diffusion. Consequently, the magnetic layer magnetic anisotropy is reduced as well as the total magnetization. However, the use of the hep buffer layer 13 prevents such adverse effects to happen on the magnetic layer 14. As a result, the magnetic anisotropy is increased, as well as the coercivity, the in-plane orientation is improved as this added buffer layer 13 provides a way to gradually match lattice parameters, and the full magnetization is obtained, that is, a "dead layer" is minimized. Moreover, the formation of smaller grains at the interface is also minimized by the provision of the buffer layer 13.

The buffer layer 13 may be formed by one or a plurality of buffer layers.

The magnetic layer 14 is made of Co or Co alloys. The Co alloys include CoCr and CoCr alloys. The magnetic layer 14 may be formed by a single layer or by a plurality of layers which behave magnetically as one layer. The magnetic layer 14 has a (1120) crystallographic orientation. The C layer 15 has a thickness of 1 nm to

5 nm, and the organic lubricant layer 16 has a thickness of 1 nm to 3 nm. The C layer 15 which may be deposited by CVD is hard and protects the magnetic recording medium not only from atmospheric degradation but also from a head or slider (both not shown) which records information on and reproduces information from the magnetic recording medium. The organic lubricant layer 16 reduces stiction between the head or slider and the magnetic recording medium, FIG. 2 is a cross sectional view showing an important part of a second embodiment of the magnetic recording medium according to the present invention. In this second embodiment of the magnetic recording medium, the present invention is applied to a longitudinal magnetic recording medium employing the SFM structure such as a magnetic disk. In FIG. 2, those parts which are the same as those corresponding parts in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted.

In the magnetic recording medium shown in FIG. 2, the magnetic layer 14 is made up of a first magnetic layer 14-1 and a second magnetic layer 14-2 which are antiferromagnetically coupled through a spacer layer 24. The first and second magnetic layers 14-1 and 14-2 are made of Co or Co alloys. The Co alloys include CoCr and CoCr alloys . The spacer layer 24 is made of Ru having a thickness of 0.6 nm to 0.9 nm, for example. The SFM structure formed by the first and second magnetic layers 14-1 and 14-2 and the spacer layer 24 is further disclosed in a Japanese Laid-Qpen Patent Application No.2001-56924 , and a detailed description on the SFM structure itself will be omitted in this specification.

FIG. 3 is a cross sectional view showing an important part of a third embodiment of the magnetic recording medium according to the present invention. In this third embodiment of the magnetic recording medium, the^' present invention is applied to a longitudinal magnetic recording medium such as a magnetic disk. In FIG. 3, those parts which are -the same as those corresponding parts in FIGS. 1 and 2 are designated by the same reference numerals, and a description thereof will be omitted.

In the magnetic recording medium shown in FIG. 3, the surface of the substrate 10 is mechanically textured as indicated by 10B. The texturing 10B on the substrate surface leads to O.R. > 1 and better SNR especially at high linear densities . Each layer of the first through third embodiments of the magnetic recording medium was formed by an in-line sputtering unit. However, the seed layer 11 and the underlayer 12 were deposited in a chamber consisting of three cathodes. The substrate 10 was rotated to obtain adequate uniformity. The compositions were based on the sputtering rates . Due to the target-to-substrate geometry, the ion trajectory was largely oblique. Usually, the texture near the disk outer portion in the case of the disk-shaped magnetic recording medium is slightly better than the texture near the inner diameter. The present inventor's experience with other intermetallic materials is that the texture is improved when single targets with 90°- incidence are employed compared to oblique sputtering. Therefore, further improvements are expected when single targets are used. A person skilled in the art will appreciate that process conditions such as substrate temperature and nitrogen partial pressure may slightly vary depending on the cathode or sputtering unit used. The structures provided are not meant to be exhaustive. For example, the magnetic layer 14 may be comprised of two or more exhanged coupled layers or of two uncoupled layers. A ^λ,pre-seed" layer (not shown) having a thickness of 1 nm to 30 nm may be formed on the substrate 10 prior to forming the seed layer 11. Although these may result in greater costs and process complexity, they are certainly not outside the scope of the present inventio . FIG. 4 shows XRD patterns for magnetic recording media with structures CoCrPtBCu(15 nm) /Cr₈₀Mo₂₀ (5 nm) /NbRuV (20 nm) /Glass, with and without NbRuV-N seed layers. In other words, the structures are made up of a CoCrPtBCu magnetic layer 14, a Cr₈₀Mo₂₀ buffer layer 13 and a NbRuV underlayer 12, with and without the seed layer 11 on the glass substrate 10. In FIG. 4, the ordinate indicates the intensity in arbitrary units, and the abscissa indicates 20 (°) . The underlayer 12 is deposited at Ts ~ 200°C, and the magnetic layer 14 is sputtered at Ts ~ 230°C.

For the magnetic recording media with the Nb_2sRu_lV₆₃ underlayer 12, the (002) and (1120) peaks are enhanced with the use of the seed layer 11, as may be seen from characteristics I-l, 1-2, 1-3 and 1- . The characteristic I-l is for the structure having the Nb₂₆Ru_lxV₆₃ underlayer 12 with the Nb₅₄Ru₁₂V₃₄- 8 seed layer 11, where a nitrogen partial pressure _N = 8%. The characteristic 1-2 is for the structure having the Nb₂₆Ru₁₁V₆₃ underlayer 12 with the Nb₅₄Ru₂₄V₂₂-N8 seed layer 11, where a nitrogen partial pressure P_N = 8% . The characteristic 1-3 is for the structure having the Nb₂₆Ru₁₁V₆₃ underlayer 12 without the seed layer 11. In addition, the characteristic 1-4 is for the structure having the Nb₁₂Ru₁₆V₇₂ underlayer 12 with the Nb₁₂Ru₁₆V₇₂ seed layer 11.

The lattice parameter a = 3.08A for the NbRuV underlayer 12, and is much larger than that for Cr (2.88A). The Co (1120) surface is ~ 4.1 A X ~ 4.3 A and is larger for CoCrPt alloys. The <110> lattice parameter of NbRuV alloys tends to fit the longer Co <110> parameter (~ 4.3A) better than the c-parameter (~ 4. lA) . When the Nb content is reduced, good texture is obtained even without the seed layer 12. The lattice parameter is also slightly reduced to 3.04 A. The Ru content of these alloys are < 20 at.% and it is possible to reduce the Ru content to < 10 at.% by increasing the V content to reduce target costs.

Underlayers employed in existing magnetic recording media tend to have a < 3. OA even for Cr alloys that have significant additives (~ 30 at.%) . According to results of experiments conducted by the present inventor, it was found that good IPO can also be obtained for larger a parameters by employing the NbRuV underlayer 12.

The addition of the buffer layer 13 as well as the longer Co <110> parameter of Pt- containing Co alloys may aid in the lattice matching between the underlayer 12 and the magnetic layer 14, where the Pt content is preferably 10 at.% or greater and 20 at.% or less for fcp longitudinal media applications, and the Pt content may be on the order of 50 at.% for fct perpendicular media applications . To obtain adequate reduction of medium emissivity, the seed layer 11 is preferably 20 nm to 30 nm thick and the underlayer 13 is preferably 10 nm to 30 nm thick. The total thickness of the seed layer 11 and underlayer 12 is preferably 30 nm to 60 nm. This preferred range of thicknesses can be deposited in just two chambers and reduces the drop in glass substrate temperature during deposition of subsequent layers .

For underlayers 12 that do not need a seed layer 11, the underlayer 12 can be deposited in two steps to achieve a sufficient thickness. The intermetallic alloy underlayer 12 has a high melting point and is expected to give rise to small grains even when made 40 nm to 60 nm thick.

FIGS . 5A through 5D show the perpendicular hysteresis loops measured with a Kerr magnetometer for three magnetic recording media on the Nb₂₆Ru_lxV₆₃ underlayer 12 having the characteristics I-l , 1-2 and 1-3 in FIG. 4. In FIGS. 5A through 5D, the ordinate indicates the Kerr rotation (°) , and the abscissa indicates the applied field (kOe) . The small coercivity and approximate linear behavior with field evidence good IPO, and the parameter h < 0.2. Further improvement is expected for direct (not oblique) sputtering from a large (> 15 cm) single target or when the hep buffer layer 13 is employed.

From a perpendicular coercivity perspective, the magnetic recording media with seed layer 11 as shown in FIG. 5B and 5C are slightly better than that shown in FIG. 5A without the seed layer 11. This result is consistent with the more pronounced (002) and (1120) peaks for magnetic recording media on the Nb₂₆Ru_ιαV₆₃ underlayer 12 with the seed layer 11 in FIG. 4. FIG. 5D shows that Nb₅₃Ru₄₇-N8 also makes a good seed layer 11 although more expensive due to the high Ru content. Best results were obtained for P_N = 8% but poor IPO was obtained when the nitrogen partial pressure P_N = 4%. FIG. 6 shows the perpendicular loop for the magnetic recording medium with the Nb₁₂Ru₁₆V₇₂ underlayer 12 having the characteristic 1-4 shown in FIG. 4. In FIG. 6, the ordinate indicates the Kerr rotation ( " ) , and the abscissa indicates the applied field (kOe) . Good IPO is obtained without an amorphous-like seed layer which is again consistent with the good crystallographic texture.

FIG. 7 shows the effects of the seed layer 11 at least for the particular 20 nm-thick underlayers 12 used, which in this case is Nb-rich Nb₄₄Ru₁₇V₃₉ for a characteristic II-l with no seed layer and for a characteristic II-2 with the seed layer 11. The seed layer 11 is Nb₃₁Ru₅₃V₁₆- , where J?_N = 8% . Seed layers with P_N = 4% revealed poor properties. Although the (110) texture exists, the enhancement is little compared to that of the (002) and Co (1120) peaks.

This can also be observed in the perpendicular loops shown in FIGS. 8A and 8B . FIGS. 8A and 8B respectively correspond to the structures having the characteristics II-l and II-2 shown in FIG. 7. FIG. 8C shows some improvement in IPO when the underlayer 12 is thinner (10 nm) than for the structure having the characteristic II-2 shown in FIG. 7. In FIGS. 8A through 8C, the ordinate indicates the Kerr rotation (°) , and the abscissa indicates the applied field (kOe) .

FIG. 9 shows plots of XRD spectra for magnetic recording media with structures CoCrPtBCu (15 nm) /Cr₈₀Mo₂₀ (5 n ) /NbV (20 nm) /Glass . In other words , the structures are ma.de up of a CoCrPtBCu magnetic layer 14, a Cr₈₀Mo₂₀ buffer layer 13 and a NbV underlayer 12, without the seed layer 11 on the glass substrate 10. In FIG. 9, the ordinate indicates the intensity in arbitrary units, and the abscissa indicates θ (°) . The underlayer 12 is made of Nb₆₅V₃₅ for a characteristic III-l, Nb₄₅V₅₅ for a characteristic III-2, and Nb₂₆V₇₄ for a characteristic III-3.

The shifting of the (002) peak to lower angles with increasing Nb content, from 26 at.% of the characteristic III-l to 65 at.% of the characteristic III-l, shows that the lattice parameter is increasing with Nb content. The (110) texture is present for underlayers 12 with significant Nb composition as ^• may be seen from the characteristics III-l and III-2, but is absent for the Nb₂₆V₇₄ underlayer 12 as may be seen from the characteristic III-3. The Co (1120) peak is also more pronounced for the characteristic III-3. FIGS. 10A, 10B and 10C respectively show the perpendicular hysteresis loops corresponding to the magnetic recording media having the characteristics III-l, III-2 and III-3 shown in FIG. 9. In FIGS. 10A through 10C, the ordinate indicates the Kerr rotation (°), and the abscissa indicates the applied field (kOe) . The lowest coercivity is exhibited by the magnetic recording medium with the Nb₂₆V₇₄ underlayer having the characteristic III-3, as may be seen from FIG. IOC. FIGS. 11A and 11B respectively show plots of the perpendicular to the film plane hysteresis loop of magnetic recording media with a Nb_x7V₈₃ underlayer 12 directly on a glass substrate 10 and on a seed layer 11 formed by oxidized NiP on the glass substrate 10. In FIGS. 11A and 11B, the ordinate indicates the Kerr rotation ( ° ) , and the abscissa indicates the applied field (kOe) .

FIG. 11A shows that good IPO can also be obtained for the magnetic recording medium with the Nb₁₇V₈₃ underlayer 12 provided directly on the glass substrate 10. FIG. 11B shows that very good IPO can be obtained especially for the magnetic recording medium with the Nb₁₇V₈₃ underlayer 12 provided directly on the NiP seed layer 12 which is provided on the glass substrate 10, as shown in FIG. 11B. As may be readily understood from the description given heretofore, NiP and reactively sputtered films of NbRuV and NbRu make good seed layers 11 for the underlayers 12 provided in the magnetic recording media according to the present invention. There may be other suitable seed layers known to those skilled in the art that are capable of improving the in-plane orientation of the underlayer, the use of which does not deviate from the spirit of the present invention. These may include alloys similar to Ni₈₁P₁₉ such as Ni₂P, Ni₃P, alloys of CrMoP, CrNiP and NbNiP, all of which allow Cr to grow with a (002) texture at Ts > 150°C. Minor modifications of the NbRuV alloy may be possible such as the addition of < 5 at.% of Al , Cr , Mn, Mo, Re, Ta , Ti or W which do not significantly affect the crystallographic texture.

Known underlayers may also be used as a template and the underlayers of the present invention may be employed to achieve larger lattice parameters than which is possible with Cr alloys. This is especially helpful when thick layers (> 10 nm) are needed, such as for emissivity or biasing purposes, as Cr-based alloys tend to develop large grains with thickness. Moreover, though the embodiments were made specifically for rigid glass substrates, the present invention may be readily applied by those skilled in the art to other substrates such as metal, polymer, plastic, or ceramic flexible and rigid substrates and still not depart from the spirit of the present invention. Next, a description will be given of a modification of the first through third embodiments of the magnetic recording medium according to the present invention described above.

In this modification, the seed layer 11 may be made of a Cr_xTi_α00__x alloy having a thickness of 10 nm to 30 nm, where x = 30 at.% to 50 at.%. The CrTi alloy may be reactively sputtered with oxygen or the surface thereof may be exposed to oxygen or air after deposition, because reactive sputtering with nitrogen does not give rise to good IPO. The CrTi alloy may be reactively sputtered in an Ar + 0₂ atmosphere.

Alternatively, the seed layer may be made of a Ti_xAl_1DC,__x alloy, where x = 40 at.% to 70 at.% or, made of a Al₅CuZr₂ alloy. In this case, the TiAl alloy may be reactively sputtered with oxygen or nitrogen. For example, the Ti₇₀Al₃₀ alloy is preferably reactively sputtered with nitrogen with a partial pressure > 5%. In addition, a AlCuZr alloy such as Al₅CuZr₂ may also be used as the seed layer 11. The AlCuZr alloy may be reactively sputtered with oxygen or nitrogen.

Furthermore, the seed layer 11 may be made of a Ru₅₀Al₅₀ alloy deposited at a temperature > 100 °C and having a thickness of 10 nm to 25 nm. The RuAl alloy provides an excellent (001) texture as well as small grain sizes. The NbRuV alloy composition of the underlayer 12 can be tuned to control the lattice parameter without relying too heavily on Cr-M alloys, where M = Mo, Ti , Nb, etc., which tend to increase in grain size with thickness on a crystalline template.

The seed layer 11 may be made of a RuAl alloy, and may be reactively sputtered with nitrogen. The RuAl alloy remains crystalline with reactive sputtering with nitrogen. However, reactive sputtering with oxygen for the RuAl alloy yields poor read/write performance.

All of the materials used for the seed layer 12 of the modification described above are either amorphous or amorphous-like. At least, no XRD signal is observed.

The underlayer 12 may be made of a NbRuV alloy with a thickness of preferably 3 nm to 15 nm. Preferably, the underlayer 12 comprises 10 at.% to 30 at.% of Nb, 10 at.% to 30 at . % of Ru , and 60 at.% to 80 at.% of V. The NbRuV-alloy underlayer 12 results in small grain sizes and promote good IPO on certain substrates or seed layers.

The Cr alloy buffer layer 13 prevents diffusion of underlayer atoms into the magnetic layer 14.

The magnetic layer 14 may have a single- layer structure as shown in FIG. 1 or, have a multilayer structure (SFM structure) shown in FIGS. 2 and 3. The magnetic layer 14 may be made of a material selected from a group consisting of CoCr, CoCrTa, CoCrPt, CoCrB, CoCrPtTa, CoCrPtB and CoCrPtBCu with a (1120) texture.

Alternatively, the magnetic layer 14 may be made of a material selected from a group consisting of CoPt, CoCrPt, CoPd and FePt with a (0002) texture. FIG. 12 shows XRD patterns for magnetic recording media with structures CoCrPtBC (18 nm)/Ru(0.8 nm) /CoCrPtBCu (3 nm) /CoCrTa (1 nm) / Cr₈₀Mo₂₀(5 n ) /NbRuV with and without air-exposed CrTi-0 seed layers 11. In other words, the structures are made up of a CoCrPtBCu second magnetic layer 14-1, a Ru spacer layer 24, a CoCrPtBCu first magnetic layer 14-1, a CoCrTa second buffer layer and a Cr₈₀Mo₂₀ first buffer layer which form the buffer layer 13, and a NbRuV underlayer 12, with and without the CrTi seed layer 11 on the glass substrate 10. In FIG. 12, the ordinate indicates the intensity in arbitrary units, and the abscissa indicates 2 θ ( ° ) .

The (002) peak (near 60°) is most pronounced for the magnetic recording medium grown directly on the glass substrate 10, that is, with no seed layer 11, where the NbRuV underlayer thickness is 40 nm, as may be seen from characteristics IV-1, IV-2 and IV-3 shown In FIG. 12. The characteristic IV-1 is for the structure having the Nb₁₄Ru_lV₇₅ underlayer 12 with the Cr₄₀Ti₆₀ seed layer 11.^' The characteristic IV-2 is for the structure having the Nb₁₄Ru_xlV₇₅ underlayer 12 with the Cr₃₀Ti₇₀ the seed layer 11. The characteristic IV-3 is for the structure having the Nb_x4Ru_xxV₇₅ underlayer 12 with no seed layer 11. The (002) peak intensity is greatly reduced for magnetic recording media with the CrTi seed layer 11 which have a thinner NbRuV under layer 12 (20 nm) , as may be seen from the characteristics IV-1 and IV-2. However, no other peaks show up except Co (1120) . It was confirmed that read/write properties improve significantly with the use of the CrTi seed layer 11. The seed layer 11 was deposited at 150 °C and the underlayer 12 was grown at 240 °C. To obtain adequate reduction of medium emissivity, the total thickness of the seed layer 11 and the underlayer 12 is preferably 25 nm to 50 nm. This preferred range of thicknesses can be deposited in just two chambers and reduces the drop in glass substrate temperature during deposition of subsequent layers.

FIGS. 13A through 13C show the perpendicular hysteresis loops measured with a Kerr magnetometer for the magnetic recording media on Nb₁₄Ru_xxV₇₅ in FIG. 12. FIGS. 13A, 13B and 13C respectively show the perpendicular hysteresis loops corresponding to the magnetic recording media having the characteristics IV-3, IV-2 and IV-1 shown in FIG, 12. In FIGS. 13A through 13C, the ordinate indicates the Kerr rotation (°) , and the abscissa indicates the applied field (kOe) . The small coercivity and approximate linear behavior with field evidence good IPO, and the parameter h < 0.2. There may be more seed layers known to those skilled in the art that are capable of improving the in-plane orientation of the underlayer 12, the use of which does not deviate from the spirit of the present invention. Minor modifications of CrTi, TiAl, and AlCuZr may be possible such as the addition of < 5 at.% of Al , Cr, Mn , Mo, Re, Ta, Ti or W which do not significantly affect the IPO and grain sizes of the NbRuV underlayer 12. Known underlayers may also be used as a template.

Next, a description will be given of an embodiment of a magnetic storage apparatus according to the present invention, by referring to FIGS. 14 and 15. FIG. 14 is a cross sectional view showing the internal structure of an important part of this embodiment of the magnetic storage apparatus, and FIG. 15 is a plan view showing the important part of the embodiment of the magnetic storage apparatus shown in FIG. 14.

As shown in FIGS. 14 and 15, the magnetic storage apparatus generally includes a housing 113. A motor 114, a hub 115, a plurality of magnetic recording media 116, a plurality of recording and reproducing heads 117, a plurality of suspensions 118, a plurality of arms 119, and an actuator unit 120 are provided within the housing 113. The magnetic recording media 116 are mounted on the hub 115 which is rotated by the motor 114. The recording and reproducing head 117 is made up of a reproducing head such as a MR and a GMR head, and a recording head such as an inductive head. Each recording and reproducing head 117 is mounted on the tip end of a corresponding arm 119 via the suspension 118. The arms 119 are moved by the actuator unit 120. The basic structure of this magnetic storage apparatus is known, and a detailed description thereof will be omitted in this specification .

This embodiment of the magnetic storage apparatus is characterized by the magnetic recording media 116. Each magnetic recording medium 116 has the structure of any of the embodiments and modifications of the magnetic recording medium described above in conjunction with FIGS. 1 through 13C. Of course, the number of magnetic recording media 116 is not limited to three, and only one, two or four or more magnetic recording media 116 may be provided .

The basic structure of the magnetic storage apparatus is not limited to that shown in FIGS. 14 and 15. In addition, the magnetic recording medium used in the present invention is not limited to a magnetic disk, and other magnetic recording media such as magnetic tapes and magnetic cards may be used. Moreover, the magnetic recording medium does not need to be fixedly provided within the housing 113 of the magnetic storage apparatus, and the magnetic recording medium may be a portable type medium which is loaded into and unloaded from the housing 113. Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.

Claims

1. A magnetic recording medium comprising : a substrate; a magnetic layer; a NbRuV alloy underlayer provided on the substrate wherein the lattice parameter is < 3.2A and > 3. OA with a predominant fiber texture of (002) ; and a buffer layer disposed between said magnetic layer and said underlayer.

2. The magnetic recording medium as claimed in claim 1, further comprising: an amorphous or crystalline seed layer disposed between said substrate and said underlayer.

3. The magnetic recording medium as claimed in claim 1 or 2 , wherein said underlayer comprises Nb = 10 at.% to 50 at.%, Ru = 5 at.% to 40 at.%, and V = 55 at.% to 85 at.% and has a thickness of 10 nm to 60 nm.

4. The magnetic recording medium as claimed in claim 1 or 2 , wherein said underlayer is made of a material selected from a group consisting of Nb₁₀Ru_X5V₇₅, Nb₁₅Ru_x5V₇₀, Nb₃₀Ru_x0V₆₀ and Nb₄₅Ru_x5V₄₀, and has a thickness of 10 nm to 60 n .

5. The magnetic recording medium as claimed in claim 1 or 2 , wherein said underlayer comprises 10 at.% to 40 at.% Nb and a remaining at.% V, with a thickness of 10 nm to 60 nm.

6. The magnetic recording medium as claimed in claim 2 , wherein said seed layer is reactively sputtered with either N₂ or 0₂ gas .

7. The magnetic recording medium as claimed in claim 6, wherein said seed layer is made of a NbRuV alloy, where Nb = 20 at.% to 60 at.%, Ru =.5 at.% to 50 at.%, and V = 10at.% to 40 at.%, and has a thickness of 1 nm to 30 nm.

8. The magnetic recording medium as claimed in claim 6, wherein said seed layer is made of an alloy selected from a group consisting of Nb₃₀Ru_4sV_2S/ Nb₄₀Ru_4SV₁₅, Nb₄₅Ru₃₅V₂₀, Nb_ssRu₂₅V₂₀ and Nb₅₅Ru₁₀V₃₅.

9. The magnetic recording medium as claimed in claim 2, wherein said seed layer is selected from a group consisting of Ni₂P, Ni₃P , Ni_8xP₁₉, alloys of CrMoP, CrNiP and NbNiP, and said seed lay.er is surface oxidized.

10. The magnetic recording medium as claimed in claim 2 , wherein said seed layer has a (002) crystallographic texture and a thickness of 10 nm to 30 nm.

11. The magnetic recording medium as claimed in claim 1, wherein said buffer layer is made of a Cr-M alloy and has a thickness of 1 nm to 10 nm, where M denotes a material selected from a group consisting of Mo, Nb, Ru , Ti , V and W of atomic proportion ≥ 10% and < 30%.

12. The magnetic recording medium as claimed in claim 1, wherein said buffer layer comprises a magnetic or nonmagnetic hep-structured

CoCr-based alloy layer having a thickness of 1 nm to 5 nm.

13. The magnetic recording medium as claimed in claim 11, wherein said magnetic or nonmagnetic hep-structured CoCr alloy layer is in direct contact with said magnetic layer.

14. The magnetic recording medium as claimed in claim 1, wherein said magnetic layer has a multi-layer structure comprising: a first magnetic layer disposed on said underlayer; a spacer layer disposed on said first magnetic layer; and a second magnetic layer disposed on said spacer layer , said first and second magnetic layers being antiferromagnetically coupled through said spacer layer .

15. A magnetic recording medium comprising: a substrate; a magnetic layer; a Nb_xRu_yV₂ underlayer; where x .> 10 at.%, y > 10 at.%, and 60 at.% < z < 80 at.%; a seed layer disposed between said substrate and said underlayer; and a Cr alloy bcc buffer layer disposed between said underlayer and said magnetic layer, said seed layer promoting small grain sizes and a (002) fiber texture for said underlayer.

16. The magnetic recording medium as claimed in claim 15, wherein said seed layer is made of a Cr_xTi_χ00__x alloy, where x = 30 at.% to 50 at.%.

17. The magnetic recording medium as claimed in claim. 16, wherein said Cr_xTi_XO0__x alloy is reactively sputtered with oxygen or its surface exposed to oxygen after deposition.

18. The magnetic recording medium as claimed in claim 15, wherein said seed layer is made of a material selected from a group consisting of Ti_xAl₁₀₀__x alloys and Al₅CuHr₂, where x = 40 at.% to 70 at.%.

19. The magnetic recording medium as claimed in claim 18, wherein said Ti_xAl₁₀₀__x alloy or said Al₅CuZr₂ alloy is reactively sputtered with oxygen or nitrogen.

20. The magnetic recording medium as claimed in claim 15, wherein said underlayer has a thickness of less than 20 nm .

21. The magnetic recording medium as claimed in claim 15, wherein said seed layer is made of a Ru₅₀Al₅₀ alloy having a thickness of 10 nm to 25 nm.

22. The magnetic recording medium as claimed in claim 21, wherein said seed layer is reactively sputtered with nitrogen.

23. The magnetic recording medium as claimed in claim 15, wherein said magnetic layer comprises a single-layer structure made of an alloy or a multi-layer structure made of alloys selected from a group consisting of CoCr, CoCrTa, CoCrPt, CoCrB, CoCrPtTa, CoCrPtB and CoCrPtBCu with a (1120) texture .

24. The magnetic recording medium as claimed in claim 15, wherein said magnetic layer is made of an alloy selected from a group consisting of CoPt, CoCrPt, CoPd and FePt with a (0002) texture.

25. The magnetic recording medium as claimed in claim 15, wherein said magnetic layer has a multi-layer structure comprising: a first magnetic layer disposed on said underlayer ; a spacer layer disposed on said first magnetic layer; and a second magnetic layer disposed on said spacer layer, said first and second magnetic ^' layers being antiferromagnetically coupled through said spacer layer.

26. A magnetic storage apparatus comprising : at least one magnetic recording medium; and a head recording information on and reproducing information from the magnetic recording medium, said magnetic recording medium comprising: a substrate; a Co alloy magnetic layer; a NbRuV alloy underlayer having a thickness of 10 nm to 60 nm disposed between said substrate and said magnetic layer, where Nb = 10 at.% to 60 at.%, Ru = 0 at.% to 40 at.%, V = 55 at.% to 85 at.%, and a lattice parameter is < 3.2A and > 3.0A with a predominant fiber texture of (002) ; and a Cr alloy bcc buffer layer having a thickness of 1 nm to 10 nm disposed between said underlayer and magnetic layer.

27. The magnetic storage apparatus as claimed in claim 26, wherein said magnetic recording medium further comprises an amorphous or crystalline seed layer disposed between said substrate and said underlayer .

28. The magnetic storage apparatus as claimed in claim 26, wherein said seed layer of said magnetic recording medium is made of a material selected from a group consisting of Nb₃₀Ru₄₅V₂₅ , Nb₄₀Ru₄₅V_ls, Nb₄₅Ru₃₅V₂₀, Nb₅₅Ru₂₅V₂₀ and Nb_5SRu_x0V_3S and has a thickness of 1 nm to 30 n .

29. The magnetic storage apparatus as claimed in claim 26, wherein said seed layer of said magnetic recording medium is made of a material selected from a group consisting of Ni₂P, Ni₃P , Ni_sxP_x9, alloys of CrMoP, CrNiP and NbNiP.

30. The magnetic storage apparatus as claimed in claim 26, wherein said buffer layer of said magnetic recording medium comprises a slightly magnetic or nonmagnetic hep-structured CoCr alloy layer having a thickness of 1 nm to 5 nm in direct contact with said magnetic layer.

31. A magnetic storage apparatus comprising: at least one magnetic recording medium; and a head recording information on and reproducing information from the magnetic recording medium, said magnetic recording medium comprising: a substrate; a magnetic layer; a NbRuV-alloy underlayer having a thickness of 3 nm to 20 nm with a predominant (002) fiber texture; a Cr alloy bcc layer, provided on said underlayer, and having a thickness of 2 nm to 10 nm; and a seed layer, disposed between said substrate and said underlayer, and having a thickness of 1 n to 30 nm.