NL8202596A - MAGNETIC REGISTRATION MEDIUM. - Google Patents

Description

r λ H3N 10,388 1 N.V. Philips' Light bulb factories in Eindhoven.

Magnetic recording medium.

The invention relates to a magnetic recording. medium containing a support of non-magnetic material with a main surface that carries a continuous layer of magnetic material with the main components Co and Cr.

5 (Digital) magnetic recording systems are used in which, on a magnetic recording medium, a transfer (or write / read) head magnetizes small areas for recording (digital) data and scans the magnetized areas for reading out the. data. For one thing, the only commercially applicable system uses longitudinal magnetic recording on a medium with a preferred direction for magnetization parallel to the medium. Longitudinal magnetic recording uses a head of the rib shape. type comprising a core of magnetic, highly permeable material having a narrow slit and placed in a flux coupling relationship with the slit transverse to the direction of movement of the magnetic recording medium. One to. a current pulse applied to the core wound, generates lines of magnetic flux in the core which close, along a path containing one edge of the slit, the portion of the magnetic medium adjacent to the slit, and the other edge of the crack. The flux passing through the medium in this way has the effect that. data is recorded. When the data is read when the magnetized area on the medium sweeps past the slit, a closing of the flux through the core is realized, whereby flux lines pass through the coil inducing an electrical signal representative of the stored information.

Such longitudinal magnetic recording systems have the drawback that the medium can only handle a limited linear bit density. This limitation occurs because the magnetized regions in the medium are magnetically oriented in the longitudinal direction of the medium. This longitudinal recording method exhibits a certain maximum demagnetizing field at the bit boundary, thereby limiting the number of o-transitions that can be stored per linear centimeter of the information track.

8202596 EHN 10.388 2 \ -: t *

In order to achieve a considerably higher linear bit density than that provided by longitudinal magnetic recording, in principle the perpendicular magnetic recording can be used. In perpendicular magnetic recording, the 5 magnetic flux passes through the medium of. the top to the bottom instead of longitudinally through the medium in the plane of the medium, to create magnetic domains perpendicular to the surface of. the medium are oriented. This recording mode exhibits a minimum demagnetizing field at the bit boundary so that a larger 1 (j) number of perpendicularly oriented transitions per linear centimeter of the medium can be undercut compared to the number of transitions in longitudinal magnetic recording systems.

From the above, it will be apparent that perpendicular magnetic recording has a greater linear packing density than longitudinal magnetic recording. Longitudinal magnetic recording is, however, widely practiced, while perpendicular magnetic recording is still in the research stage to date. One of the reasons why perpendicular magnetic recording has not hitherto been applied on a commercial scale is presumably due to the fact that suitable recording media are not yet available that indeed have the advantages of perpendicular magnetic recording. from. can be achieved.

In the article. Co-Cr perpendicular recording medium by vacuum deposition by. R. Sugita et al., Published in trrr Transactions 25 on Magnetics, Vol. Mag-17, No. 6, November 1981, biz. 3172-74 (1), for perpendicular magnetic recording, the application of vapor deposited Co. Cr films described. The saturation magnetization (f) of such I-XXs films decreases very sharply with x ((ƒ # 0 at x ^ O.25). High (f-values ss can be obtained there since low Cr concentrations. Co-Cr films, as perpendicular recording media, in addition to a high f, also require a high coercive force In addition, the magnetization must be perpendicular to the substrate plane.These additional requirements can only be realized for relatively high Cr concentrations. This means that one has to look for an optimum concentration for which f has not fallen too much yet, although the perpendicular symmetry requirement has already been met. In literature such optimal combinations of parameters have been described in various places:

Table I: 8202596 1 + * τ ΡΗΝ 10,388 3

Ref. Cf (emu / cm?) G ^^ emn / cm ^) (Oe)

Sugital et al. (T) 280 60 700

Maeda et al. (2). 210.24 300-400

Kobayshi et al. (3) 317 100 1000

See Y. Maeda et al, Japanese Journal of Applied Physics, 20, 1981, p.

1467 (2) and K. Kobayashi et. already,. Journal o Applied Physics, 52, March 1981, 1 (J pp. 2453-55 (3).

The object of the invention is a registration I

provide perpendicular recording mode medium with significantly improved properties.

This problem is solved by a recording medium of the type described in the opening paragraph, characterized in that the layer 15 also contains Pt, in an amount of more than 1 at% to a maximum of 5 at%.

The addition of the said small amount of Pt to Co-Cr alloys, in particular to Co-Cr alloys which. 15 to 30at%

In crie, it has been found that an increase in saturation magnetization C11 by more than 100% while retaining the perpendicular anisotropy and the high value of the coercive force.

A. The embodiment of the invention will be explained in more detail by way of example with reference to the drawing.

Figure 1a is a side view of a vertical type data storage device with a recording medium and a transfer head.

25

Figure 1b is a cross-sectional view of the transfer head of Figure 1a taken along line 1B-TB.

Figure 2 is a graph showing field H along the X axis, when energizing the transfer head of Figure 1.

Figure 3 is a graph showing the Ó'-H loop in the first two quadrants of an Oo-Cr-Pt alloy.

Figures 1a and 1b show a side view of a perpendicular recording device with transfer head 11 and recording medium 14, respectively, and a cross-section of the transfer head used with this device. A U-shaped core 1 of magnetically high permeable material such as a nickel-iron alloy with 80 at% nickel and 20 at% iron has been applied to a substrate 2 in the form of a thin film molecular technique such as sputtering. The core 1 comprises 8202596 “lux> ΡΗΝ 10,388 4 a transfer leg 3 and a f lux return leg 4 which are just connected via an intermediate core part 5. As shown in figure 1b, the layer thickness of the core 1 at the location of the transfer leg 3 d ^ and at the location of the flux return leg 4 with d2> d ^, while the end of the transfer leg 3 has a width and the end of the flux return leg 4 has a width W2 · The cross-sectional area of the end of leg 3 (which determines the achievable bit density per unit area) is therefore Wj. d ^ and the cross-sectional area of the leg 4 is thus W2. d2 · In the transfer leg 3, a coil 6 is provided. In order that 10 leg 4 does not write when coil 6 is energized, W2. d2 are significantly greater than. d ^, preferably at least 5 to 10 times as large. When recording medium 14 moves perpendicular to the plane of the paper at a speed "iT" as shown in Figure 1a, the thickness determines dimension d ^ of the end of the transfer leg 3 which can be between 0.1 and 15 µm. the number of flux transitions per linear centimeter.

The width size of the transfer leg 3, which can be between 2 and 20 µm, then determines the width of the track that is written on the recording medium. In use, the core 1 is, for example, at a height h above the moving magnetic medium 14. In so-called 2Q in-contact registration, h can be zero. The medium 14 can be a magnetic disk or tape with a non-magnetic support 8 which carries a magnetic layer 7 having a perpendicular magnetic anisotropy.

When a data coded current is supplied to the coil 6 (shown a coil with ten turns), a closed path for the magnetic flux is generated in leg 3, intermediate core part 5, leg 4, the air gap with the large cross section, the medium 7, the return path 8, the magnetic layer 7 opposite leg 3 where the actual registration is established, the air gap with the small cross section S2 and back to leg 3.

3fl By polishing the current in a desired way, domains with perpendicular, but opposite, magnetization are created in the magnetic layer 7.

The distance S between the transfer leg 3 and the flux return leg 4 is sufficient to prevent flux from crossing directly from leg 3 to leg 4 during the writing process. Moreover, the distance S is such that it provides space for the rinse the transfer leg 3 for 6 cm.

In order to make optimum use of the perpendicular magnetic recording mode, the size should preferably be between 2 and 20 µm, in this case a size of 5 µm is a characteristic value, while the size d ^ Mj should preferably be between 0.1 and 1 µm, a size of 0.2 ^ um is a characteristic value in this case, g Figure 2 shows the writing field H (the field which, when energizing coil 6 is generated by the head 11 via the connecting wires 9, 10), measured in the x direction. In the region Rj corresponding to the location of the transfer leg 3, the writing field is very high in it. area corresponding to the location of flux return leg 4, field 10 is so much lower that it is not written. In addition, since sharp singularity occurs in the writing field at sharp angles, which may lead to writing inadvertently, the angles 12, 13 of flux return leg 4 are rounded. In reading operations, due to the large "capture" cross-section of the flux return leg 4, any information read will mean and will not make an effective contribution to the signal read by transfer leg 3.

According to the invention, the magnetic layer 7 contains a Co-Cr alloy to which a certain small amount of Pt has been added. The layer has a thickness of about 500 nm.

20 The research described by Maeda (2) shows that tetragonal phase can also occur in vaporized Co-Cr films in addition to the hexagonal hcp phase. The simultaneous nucleation and growth of hops and tetragonal crystallites hinders the creation of a microstructure in which the hcp phase crystallites have a growth direction with their c-axis perpendicular to the substrate surface. This annoying tetragonal phase can be suppressed by applying low sub-substrate temperatures (130-150 ° C.). Given that heating of the substrate always occurs during the evaporation process, correct adjustment of such low substrate temperatures is nevertheless very difficult.

As described by Maeda et al. (2), such low substrate temperatures entail the risk that, in addition to the phases described above, an FCC phase may also occur at the expense of the desired HCP phase. The presence of this FCC phase is extremely annoying because it induces a growth direction [100 J perpendicular to the substrate of the HCP phase, so that of course the perpendicular preferred direction is lost.

The present invention is based on the fact that the rates of nucleation and growth are strongly influenced by the addition of Pt.

8202596 PHN 10.388 6 - In particular, the addition of more than 1% Pt has succeeded in suppressing the formation of the tetragonal and FCC phase. According to an examination of the metal films by X-ray, the orientation of the crystallites corresponds to a direction 5 in which their hexagonal, c-axis is perpendicular to the substrate plane. A surprising result. the enormous increase in the saturation magnetization (by more than 100% when adding only 2% Pt).

An example of magnetic measurement results can be seen in FIG.

3. Further results are summarized in Table II:

10 Table II

Co1-A Ky ^ <G> Hcx (0b> Hc H <0S) x = 0.25 y * 0.05. 522 1100 700 15 0.23 0.05 880 1500 600 0.25 0.03 880 1250 600 '0.22 0.03 1050 900 500 0.28 0.03 723 800 400 0.18 0.03 746 1000 500 20 0.22 0.02 522 1000 500 0.18 0.02 676 900 350 0.22 0.01 494 350 350

Figure 3 shows the room temperature hysteresis loop of one in one non-magnetic support of. for example, a plastic material such as polyester vapor-coated CoQ ^ qCTq 22FtQ 02 one of about 500 nm. The value of the perpendicular remanence (^^ clearly exceeds the value of the parallel retentivity (JL „which makes the alloy K i | t in question ideally suited for the perpendicular registration mode. 30 When the layer is less than 1 at.%. Pt contains does not exceed CfR ||.

The layer was prepared in the following manner. Pasture on a quartz substrate, placed in a UHV clock. a vapor mixture of the metals COr Cr and Pt. knocked down. The vapor mixture was obtained by three separate electron beam diffusers whose evaporation rates could be controlled independently by quartz crystal oscillators. The substrate temperature was about 250 ° C. The geometric arrangement of the three sources (evaporators) can be characterized by 8202596 PHN 10.388 7 an equilateral triangle, with a source qp at each of the angles. The substrate is located vertically above the center of gravity of the triangle with about 30 cm distance between the source and substrate. The angle of attack of the vapor flux with respect to the normal on the substrate surface is about. 15 degrees. The vapor velocities varied between 10 and 20 µl / sec. The 0 -8 base pressure in the UHV-klck before evaporation was better than 1.3.10 Pa and during the evaporation 1.10 Pa.

The process outlined above lends itself well. for laboratory scale experiments when it is desired to vary the composition of the vapor deposited 1Q layers. However, for factory production, it is more appropriate to use a single flash source consisting of an alloy of the metals in question if it has been decided on a particular composition. In addition to vapor deposition, sputtering is also suitable for applying the layers to a substrate.

15 20 25 30 8202 596 35

Claims (1)

Recording medium according to claim 1, characterized in that! the layer contains 15 to 30 at% Cr. ! i i; i; t i * 15 20 25 30 8202596 35