JP2013073635A - Alloy and sputtering target material used for soft magnetic thin film layer in perpendicular magnetic recording medium and perpendicular magnetic recording medium having soft magnetic thin film layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic alloy for a perpendicular magnetic recording medium showing a small reduction in Bs (Saturation Magnetic Flux Density) at high temperature with respect to Bs at room temperature, and to provide a sputtering target material for producing a thin film of the alloy.SOLUTION: The alloy used for the soft magnetic thin film layer in the perpendicular magnetic recording medium comprises: at least one element belonging to lanthanoid with atomic numbers from 57 to 71; at least one of Y, Ti, Zr, Hf, V, Nb, Ta and B and/or at least one of C, Al, Si, P, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Mo, Sn and W; and the balance of Co, Fe and inevitable impurities, satisfying the following formulas (1) to (3) in terms of at%. They are (1):0.5≤TLA≤15, (2):5≤TLA+TAM, and (3):TLA+TAM+TNM≤30.

Description

  The present invention relates to a (Co, Fe) -lanthanoid alloy and a sputtering target material for a soft magnetic thin film layer in a perpendicular magnetic recording medium.

The progress of magnetic recording technology has been remarkable, and in order to increase the capacity of the drive, the recording density of the magnetic recording medium has been increased, and a higher recording density can be realized than the in-plane magnetic recording medium that has been popular in the past. A perpendicular magnetic recording system has been put into practical use. The perpendicular magnetic recording system is a method suitable for high recording density, in which the easy magnetization axis is oriented in the perpendicular direction with respect to the medium surface in the magnetic film of the perpendicular magnetic recording medium. In the perpendicular magnetic recording system, a two-layer recording medium having a magnetic recording film layer and a soft magnetic film layer with improved recording sensitivity has been developed. A CoCrPt—SiO ₂ alloy is generally used for the magnetic recording film layer.

  On the other hand, a conventional soft magnetic film layer needs to have a high saturation magnetic flux density (hereinafter referred to as Bs) and an amorphous property. Further, depending on the application and use environment of the perpendicular magnetic recording medium, it has high corrosion resistance and high hardness. Various characteristics have been additionally required. For example, in JP 2008-299905 A (Patent Document 1), high Bs is obtained by adding Fe, and high hardness is obtained by adding B. In JP 2011-68985 A (Patent Document 2), corrosion resistance (weather resistance) is improved by adding Y or Ti.

In recent years, writing with a lower magnetic flux than before has been achieved by improving the read / write head during driving and adjusting the magnetic flux density of the soft magnetic alloy to optimize the exchange coupling magnetic field between the soft magnetic film and the Ru film. It has become possible. Therefore, as a soft magnetic layer disposed under the recording layer, an amorphous alloy having a relatively low Bs instead of the conventional high Bs has been studied. When a low Bs alloy is used as a soft magnetic layer of a perpendicular magnetic recording medium in this way, the recording magnetization in the soft magnetic film does not excessively affect the surroundings and can be recorded in a small space as a result. Become. This phenomenon is considered to improve the apparent recording density by reducing the “writing blur”.
JP 2008-299905 A JP 2011-68985 A

  However, when an amorphous alloy having a low Bs is used for the soft magnetic layer of a perpendicular magnetic recording medium as described above, it has become clear that there is a new problem. That is, an amorphous alloy having low Bs has a large decrease range of Bs as the temperature rises, and Bs under a temperature environment (for example, about 70 to 150 ° C.) higher than room temperature to which the drive is exposed becomes remarkably low. The function as the soft magnetic layer of the perpendicular magnetic recording medium cannot be sufficiently performed.

  In order to solve the problems as described above, the inventors examined various additive elements in detail for Bs and its temperature characteristics at room temperature of the soft magnetic film alloy of the perpendicular magnetic recording medium. It has been found that there is an inverse correlation between Bs and the decrease in Bs from room temperature to 150 ° C. However, the addition of an element belonging to the lanthanoid deviates from this inverse correlation, and the present inventors found that the Bs reduction range up to 150 ° C. can be significantly reduced compared with an alloy having the same Bs at room temperature. . That is, a soft magnetic alloy for a perpendicular magnetic recording medium having a high saturation magnetic flux density at a high temperature relative to a saturation magnetic flux density at room temperature, and a sputtering target material for producing a thin film of this alloy are provided.

The gist of the invention is that
(1) at least one element belonging to a lanthanoid having an atomic number of 57 to 71 and at least one element selected from Y, Ti, Zr, Hf, V, Nb, Ta, B, and / or C , Al, Si, P, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Mo, Sn, W and the balance Co, Fe and inevitable impurities, and the following formula ( An alloy used for a soft magnetic thin film layer in a perpendicular magnetic recording medium characterized by satisfying all of 1) to (3). (1) 0.5 ≦ TLA ≦ 15
(2) 5 ≦ TLA + TAM
(3) TLA + TAM + TNM ≦ 30
However, TLA is the total% of the amount of elements belonging to the lanthanoids of atomic number 57 to 71
Total amount of TAM = Y + Ti + Zr + Hf + V + Nb + Ta + B / 2 addition amount
Note that only B is 1/2 times the value.
TNM = total amount of addition amount of C + Al + Si + P + Cr + Mn + Ni + Cu + Zn + Ga + Ge + Mo + Sn + W

(2) A soft magnetic thin film layer made of the alloy according to (1).
(3) A perpendicular magnetic recording medium having the soft magnetic thin film layer according to (2).
(4) A sputtering target material comprising the alloy according to (1).
(5) A soft magnetic thin film layer formed from the sputtering target material according to (4).
(6) A perpendicular magnetic recording medium having the soft magnetic thin film layer according to (5).

  As described above, according to the present invention, the soft magnetic alloy for perpendicular magnetic recording media has a small decrease in Bs at a high temperature relative to Bs at room temperature, that is, a high temperature of about 70 to 150 ° C. at which the drive is exposed during use. And providing a sputtering target material for producing a thin film of this alloy. By using the alloy of the present invention for a perpendicular magnetic recording medium, the magnetic properties of the soft magnetic alloy can be fully exhibited and the function of the soft magnetic thin film layer can be sufficiently enhanced. As a result, the perpendicular magnetic recording can be performed. This can lead to an improvement in the performance of the medium.

Hereinafter, the present invention will be described in detail.
As described above, Bs at room temperature and its temperature characteristics of the soft magnetic film alloy of the perpendicular magnetic recording medium were examined in detail for various additive elements. As a result, Bs at room temperature and Bs from room temperature to 150 ° C. It was found that there was an inverse correlation between the drop widths. However, when an element belonging to a lanthanoid was added, it was found that the inverse correlation relationship was removed, and the Bs decrease width up to 150 ° C. was significantly reduced as compared with an alloy having an equivalent Bs at room temperature.

Although the detailed reason for the above phenomenon is unknown, the following is presumed. The exchange integral (Je) is considered to affect the temperature characteristics of Bs. In the case of a crystalline metal, the principle is unknown, but it is suggested that Je may change depending on the 3d electron orbit and the interatomic distance (so-called). Bethe-Slater curve). Here, the element belonging to the lanthanoid in which the effect of improving the temperature characteristic of Bs was observed in the present invention has an atomic radius in the crystal of 1.73 to 1.99 × 10 ⁻¹⁰ m, which is significantly larger than other elements. . Therefore, it is considered that the average interatomic distance is increased in the amorphous alloy to which the elements belonging to these lanthanoids are added. As a result, the same effect as the increase in Je due to the increase in the interatomic distance in the crystalline alloy appears. It is assumed that the high temperature characteristics are improved.

  In fact, as shown in the example of the X-ray diffraction of the quenched ribbon sample in FIG. 1, when the element belonging to the lanthanoid is added, the skirt on the low angle side of the halo pattern is gentler than when adding other elements. It is confirmed that it has expanded. This suggests that the average interatomic distance of the amorphous alloy was increased by adding an element belonging to a lanthanoid having a large atomic radius.

The characteristics and operation of the amorphous soft magnetic alloy found by the present invention based on the above findings and having a small Bs decrease width at high temperatures relative to Bs at room temperature will be described below. The element belonging to the lanthanoid having an atomic number of 57 to 71 refers to La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
Formula (1) 0.5 ≦ TLA ≦ 15 (TLA is the total% of the amount of elements belonging to the lanthanoids having atomic numbers 57 to 71)
Formula (2) 5 ≦ TLA + TAM (TAM = Y + Ti + Zr + Hf + V + Nb + Ta + B / 2) Total amount of addition amount, B alone being 1/2 times the value.
Formula (3) TLA + TAM + TNM ≦ 30 (TNM = C + Al + Si + P + Cr + Mn + Ni + Cu + Zn + Ga + Ge + Mo + Sn + W total%)

  In the alloy of the present invention, the element belonging to the lanthanoids having atomic numbers 57 to 71 is an essential element for lowering Bs at room temperature and suppressing the decrease of Bs at high temperature, and also has an amorphous promoting effect. Moreover, in the material of the alloy composition of the present invention when crystalline, it is also an element that forms brittle intermetallic compounds with Co and / or Fe. In the alloy of the present invention, Y, Ti, Zr, Hf, V, Nb, Ta, and B are elements that lower Bs at room temperature and have an amorphous promoting effect.

  In the alloy of the present invention, C, Al, Si, P, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Mo, Sn, and W are elements added to reduce Bs at room temperature. Therefore, if the TLA is less than 0.5, the effect of suppressing the decrease in Bs at high temperatures is not sufficient, and if it exceeds 15, a large amount of brittle intermetallic compounds are produced. Processing becomes difficult. Further, if TLA + TAM is less than 5, the amorphous promoting effect is not sufficient. Further, when TLA + TAM + TNM exceeds 30, Bs at room temperature becomes excessively low. In addition, the preferable range of each formula is as follows.

  For formula (1), preferably 1 ≦ TLA ≦ 13, more preferably 2 ≦ TLA ≦ 11. For formula (2), preferably 6 ≦ TLA + TAM, more preferably 7 ≦ TLA + TAM. Preferably about Formula (3), it is TLA + TAM + TNM <= 28, More preferably, it is TLA + TAM + TNM <= 26. The range of the ratio of the Fe content and the total content of Fe and Co (hereinafter referred to as “Fe% / (Fe% + Co%)”) is not particularly limited, but the softness of the perpendicular magnetic recording medium is not limited. As the magnetic film, those more than 0 and 0.90 or less are often used, and those having a value of 0.30 or more and 0.65 or less are more used.

Hereinafter, the present invention will be specifically described with reference to examples.
Usually, a soft magnetic film layer in a perpendicular magnetic recording medium can be formed on a glass substrate or the like by sputtering a sputtering target material having the same component. Here, the thin film formed by sputtering is rapidly cooled. On the other hand, in the experiments A and B shown below, a quenching ribbon manufactured by a single roll type liquid quenching apparatus is used as a specimen. This is a simple evaluation of the influence of the components on various properties of a thin film formed by quenching by sputtering in a simple manner using a liquid quenching ribbon.

Next, as Experiment C, a sputtering target material was actually produced and a thin film produced by sputtering was evaluated.
Regarding the conditions for preparation of the quenched ribbon, 30 g of raw material weighed to a predetermined component was arc-melted in reduced-pressure Ar using a water-cooled copper mold having a diameter of about 10 mm and a depth of about 40 mm to obtain a molten preform for the quenched ribbon. . The conditions for preparing the quenched ribbon are a single roll method, set in this molten base material in a quartz tube having a diameter of 15 mm, a diameter of the hot water nozzle is 1 mm, an atmospheric pressure of 61 kPa, a spray differential pressure of 69 kPa, a copper roll (diameter of 300 mm). ) Was set at 3000 rpm and the gap between the copper roll and the hot water nozzle was set to 0.3 mm, and the hot water was discharged. The hot water temperature is not particularly limited, and the hot water is discharged immediately after each molten base material is completely melted. The quenched ribbon thus prepared was used as a test material, and Bs and amorphous properties at room temperature and high temperature were evaluated.

  Regarding the evaluation of Bs at room temperature and the Bs decrease width at high temperature (150 ° C.) of the quenched ribbon, using a VSM apparatus (vibrating sample type magnetometer) with an applied magnetic field of 1200 kA / m at room temperature (30 ° C.) and 150 ° C. Bs was measured. In addition, the decrease width of Bs at high temperature was evaluated by the percentage of Bs at 150 ° C. with respect to Bs at 30 ° C., that is, (Bs at 150 ° C.) / (Bs at 30 ° C.) × 100%. . (Hereinafter referred to as “Bs ratio”). That is, the closer this Bs ratio is to 100%, the smaller the decrease in Bs from 30 ° C to 150 ° C.

Regarding the evaluation of the amorphous property of the quenched ribbon, usually, when an X-ray diffraction pattern of an amorphous material is measured, a diffraction peak is not seen and a halo pattern peculiar to an amorphous state is obtained. Moreover, when it is not completely amorphous, although a diffraction peak is seen, a peak height becomes low compared with a crystalline material, and a halo pattern is also seen. Therefore, amorphousness was evaluated by the following method.
The test material was attached to a glass plate with a double-sided tape, and a diffraction pattern was obtained with an X-ray diffractometer. At this time, the test material was affixed on the glass plate so that the measurement surface was a copper roll contact surface of a quenched ribbon. The X-ray source was Cu-kα ray, and measurement was performed at a scan speed of 4 ° / min. In this diffraction pattern, the evaluation of the amorphous property was evaluated as ◯ when the halo pattern could be confirmed, and x when no halo pattern was observed.

  For the evaluation of the machinability of the sputtering target material, 5 kg of a base material weighed to a predetermined component was induction-melted in a refractory crucible under a reduced Ar atmosphere and then solidified. The size of the crucible is 120 mm in diameter and 150 mm in height. From the lower part of the ingot, a sputtering target material having a diameter of 95 mm and a thickness of 2 mm was produced by lathe processing, wire cutting processing, and plane polishing processing. Machinability was evaluated by the occurrence of chips and cracks during these processes.

For the evaluation of the sputtered film, the atmospheric pressure in the chamber was evacuated to 1 × 10 ⁻⁴ Pa or less, and Ar gas having a purity of 99.9% was added until the pressure reached 0.6 Pa to perform sputtering. The thin film was formed on the glass substrate so as to have a thickness of 1.5 μm. About this thin film sample, Bs and Bs ratio, and the crystal structure were evaluated similarly to the quenched ribbon. First, two basic compositions were selected, a certain amount of additive element was added to each, and changes in Bs and Bs ratio at room temperature depending on the type of additive element were evaluated. The results are shown as Experiment A and Experiment B. In Experiment A, an alloy in which Co is 39%, Fe is 39%, Zr is 8%, B is 6%, and the remaining 8% is an additive element, and the additive element under a constant addition amount is prepared. The effect of type was evaluated. In addition, No. 11 is an alloy containing no additive elements and blended so that Co, Fe, Zr, and B are 43: 43: 8: 6.

表１は、様々な元素を添加した急冷薄帯の諸特性を示す。Ｎｏ．１〜１０は本発明例であり、Ｎｏ．１１〜３１は比較例である。

Table 1 shows various properties of the quenched ribbon with various elements added. No. 1 to 10 are examples of the present invention. 11 to 31 are comparative examples.

FIG. 2 shows a plot of room temperature Bs and Bs ratio in Table 1. FIG. 2 shows that the composition added with an element other than the element belonging to the lanthanoid shows a correlation in which the Bs ratio also decreases with a decrease in Bs at room temperature, whereas the composition added with the element belonging to the lanthanoid clearly It can be seen that the Bs ratio is high despite the low Bs at room temperature.
Experiment B is an alloy in which Co is 39.6%, Fe is 48.4%, Ti is 3%, Zr is 2%, Nb is 3%, Ta is 2%, and the balance is 2%. And the effect of the type of additive element under a constant addition amount was evaluated. In addition, No. 11 is an alloy containing no additive elements and blended so that Co, Fe, Ti, Zr, Nb, and Ta are 40.5 to 49.5 to 3 to 2 to 3 to 2.

表２は、様々な元素を添加した急冷薄帯の諸特性を示す。Ｎｏ．１〜４は本発明例であり、Ｎｏ．５〜１４は比較例である。

Table 2 shows various properties of the quenched ribbon with various elements added. No. 1-4 are examples of the present invention. 5-14 are comparative examples.

  FIG. 3 shows a plot of room temperature Bs and Bs ratio in Table 2. FIG. 3 shows that the composition in which an element other than the element belonging to the lanthanoid is added has a correlation in which the Bs ratio also decreases with a decrease in Bs at room temperature. It can be seen that the Bs ratio is high despite the low Bs at room temperature.

  From the above experiments A and B, it has been clarified that when an element belonging to a lanthanoid is added, a high Bs ratio can be obtained for a composition having the same degree of Bs as compared with the case where other elements are added. Next, in various compositions, sputtering target materials were prepared and used for 10 pairs of compositions in which the elements belonging to the lanthanoids were added and the compositions in which the elements were not added and having almost the same amount of Co and Fe. The sputtered thin film was evaluated (Experiment C).

  In addition, A to J and a to j in Experiment C are compared by comparing compositions having equivalent amounts of Co and Fe in pairs, so that almost equivalent Fe% / (Fe% + Co%) and Bs at room temperature. It has been confirmed that the Bs ratio changes depending on whether or not 0.5% or more of the element belonging to the lanthanoid is contained. Experiment C evaluated the Bs, Bs ratio, and amorphous property of the sputtered film having various compositions at room temperature.

表３は、スパッタ薄膜の諸特性を示す。Ａ〜Ｊは本発明例であり、ａ〜ｊは比較例である。

Table 3 shows various properties of the sputtered thin film. A to J are examples of the present invention, and a to j are comparative examples.

  In the comparative example, the element (TLA in the table) belonging to the lanthanoid of the present invention example is replaced with another additive element. For example, Comparative Example a is an example in which 5% Zr is added in place of 2% Nd and 3% Gd added in Invention Example A. Thus, the effect of TLA was verified by replacing TLA with other additive elements.

表４のように、それぞれ対となる組成は、ほぼ同等のＣｏおよびＦｅ量であることから、室温でのＢｓの差は０．０８Ｔ以下と小さい。一方、Ｂｓ比は、Ｊとｊ以外の対においてランタノイドに属する元素を０．５％以上含む組成（Ａ〜Ｉの試料）の方が０．２％以下の組成（ａ〜ｉの試料）より、１〜１０％高いことが分かる。また、Ａ〜Ｉおよびａ〜ｉのスパッタリングターゲット材はいずれも欠けなく加工可能であった。

As shown in Table 4, since the paired compositions have almost the same amount of Co and Fe, the difference in Bs at room temperature is as small as 0.08 T or less. On the other hand, the Bs ratio is 0.2% or less for the composition containing 0.5% or more of the element belonging to the lanthanoid in the pair other than J and j (samples for a to i) (sample for a to i). It can be seen that it is 1-10% higher. Moreover, all of the sputtering target materials A to I and a to i could be processed without chipping.

  The sample of J was not chipped during machining, but the sample of j was made of three sputtering target materials, but two of them were broken and could not be made, and the other one was made but chipped. There has occurred. Furthermore, since the sample of j has a large TLA + TAM + TNM of 31, Bs at room temperature is excessively low.

It is a figure which shows the X-ray-diffraction pattern of the alloy of 39% Co-39% Fe-8% Zr-6% B-8% (addition element) made from a quenching ribbon. It is the figure which plotted Bs and Bs ratio of room temperature in Table 1. It is the figure which plotted Bs and Bs ratio of room temperature in Table 2.

Claims (6)

and at least one element belonging to a lanthanoid having an atomic number of 57 to 71 and at least one element selected from Y, Ti, Zr, Hf, V, Nb, Ta, B or / and C, Al, It contains one or more of Si, P, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Mo, Sn, and W, and consists of the remainder Co, Fe and unavoidable impurities. An alloy used for a soft magnetic thin film layer in a perpendicular magnetic recording medium characterized by satisfying all of (3) to (3).
(1) 0.5 ≦ TLA ≦ 15
(2) 5 ≦ TLA + TAM
(3) TLA + TAM + TNM ≦ 30
However, TLA is the total% of the amount of elements belonging to the lanthanoids of atomic number 57 to 71
TAM = Y + Ti + Zr + Hf + V + Nb + Ta + B / 2% of the total amount added, B alone being 1/2 times the value.
TNM = total amount of addition amount of C + Al + Si + P + Cr + Mn + Ni + Cu + Zn + Ga + Ge + Mo + Sn + W A soft magnetic thin film layer made of the alloy according to claim 1. A perpendicular magnetic recording medium having the soft magnetic thin film layer according to claim 2. A sputtering target material comprising the alloy according to claim 1. A soft magnetic thin film layer formed from the sputtering target material according to claim 4. A perpendicular magnetic recording medium having the soft magnetic thin film layer according to claim 5.

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