TWI544092B - An alloy for a soft magnetic thin film layer of a vertical magnetic recording medium, and a sputtering target material and a perpendicular magnetic recording medium having a soft magnetic film layer - Google Patents

Description

Alloy for soft magnetic film layer of perpendicular magnetic recording medium and sputtering target and perpendicular magnetic recording medium having soft magnetic film layer [Reciprocal reference of related applications]

The application is based on the priority of Japanese Patent Application No. 2011-212045, filed on Sep. 28, 2011, the entire disclosure of which is hereby incorporated by reference.

The present invention relates to an alloy for a soft magnetic film layer and a sputtering target for a perpendicular magnetic recording medium.

In recent years, the magnetic recording technology has progressed remarkably, and in order to increase the capacity of the device, the high recording density of the magnetic recording medium has been continuously evolved, and the perpendicular magnetic density of the recording density higher than that of the longitudinal magnetic recording medium which has been popularized for a while can be realized. The recording method is practical. The perpendicular magnetic recording method is a method in which the medium surface in the magnetic film of the perpendicular magnetic recording medium is formed such that the easy magnetization axis is aligned in the vertical direction, and is suitable for a high recording density. Further, in the perpendicular magnetic recording method, a two-layer recording medium having a magnetic recording film layer and a soft magnetic film layer for improving recording sensitivity is being developed. As the magnetic recording film layer, a CoCrPt-SiO ₂ -based alloy is generally used.

On the other hand, in the conventional soft magnetic film layer, high saturation magnetic flux density (hereinafter referred to as Bs) and high amorphous energy formation energy (hereinafter referred to as amorphous property) are necessary, and further according to vertical The use or environment of the magnetic recording medium can be supplemented with various requirements such as high corrosion resistance and high hardness. Characteristics. Among the above-mentioned required characteristics, in particular, high Bs is important, and Japanese Patent Laid-Open Publication No. 2008-299905 (Patent Document 1) or JP-A-2011-68985 (Patent Document 2) and Japan In the patent publication No. 2011-99166 (patent document 3), attention is paid to high Bs, and in any of the examples, it is 1.1 T or more, and when it is limited to the amorphous state, it is 1.3 T or more, so that it is actually heard that the magnetic field is perpendicular. When using a sputtering film as a sputtering film, it is necessary to have a Bs of approximately 1.3T or more.

In order to stabilize the magnetization of the recording film, it is necessary to consider the magnetization of the recording film in consideration of the above, and it is necessary to have a magnetic anisotropy in the plane direction of the recording medium (hereinafter, it is referred to as planar magnetic anisotropy). (Hk)). In particular, high Hk is an important factor for reducing noise, and it is known that the Bs of a soft magnetic film is generally high, which is a large value.

However, there are also disadvantages caused by the use of a soft magnetic film of high Bs. In other words, when a soft magnetic film having a high Bs is used in a state where the magnetic head is magnetized by the writing head, since the magnetic flux density is high, the surrounding wide range is affected by the magnetic influence, and the result is affected. It is necessary to obtain a large space necessary for writing information per unit of recording information, and it is difficult to increase the recording density. This phenomenon is also known as "bleeding."

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-299905

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-68985

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-99166

From the background of the above, the present invention has a minimum Bs for stabilizing the magnetization of the recording film, but it has been found that a soft magnetic alloy having a high Hk even at a relatively low Bs can be considered to reduce the high Hk. Causes noise, and suppresses "bleeding" to obtain high recording density. Therefore, in order to increase the Hk, it is important to review the influence factors other than the high Bs and to realize the soft magnetic amorphous alloy.

Here, it is not the case that high Hk is obtained by high Bs as in the past, and the results of other influence factors on Hk are reviewed, and it is presumed that it is effective to determine the temperature characteristic of high Bs (high courtesy point), and according to the technical idea, low Bs is used. The method of alloying with high-temperature characteristics of high Bs has found that high Hk and reduced osmosis can be achieved, and the present invention has been completed.

Accordingly, an object of the present invention is to provide a soft magnetic alloy for a perpendicular magnetic recording medium which exhibits a low saturation magnetic flux density at room temperature and which has a small decrease in saturation magnetic flux density at a high temperature, and is used for producing the same A sputtering target for a thin film of an alloy.

According to one aspect of the present invention, there is provided an alloy for a soft magnetic film layer in a perpendicular magnetic recording medium, the alloy being at%, including: one or more than Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Ni, Cu, Al, B, C, Si, P, Zn, Ga, Ge, Sn; the remaining part Co, Fe; and, inevitable impurities Preferably, consist essentially of these elements (consisting essentially More) is composed of only these elements (consisting of); all satisfy the following mathematical formulas (1) to (3): (1) 0 ≦ Fe% / (Fe% + Co%) ≦ 0.5

(2) 5≦Ti%+Zr%+Hf%+V%+Nb%+Ta%+B%/2

(3) 0.3≦0.813×Fe%/(Fe%+Co%)-0.062×TNM+1.751≦1.2 (In the mathematical formula, Fe%/(Fe%+Co%) is the content of Fe, and the total Fe and Co Ratio of content; TNM is the addition of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Ni, Cu, Al, B, C, Si, P, Zn, Ga, Ge, Sn The total amount of the amount is, however, the value of B is only 1/2 times).

According to another aspect of the present invention, a soft magnetic film layer composed of the above alloy is provided. According to still further aspects of the present invention, a perpendicular magnetic recording medium having the above soft magnetic film layer is provided. According to still further aspects of the present invention, a sputtering target composed of the above alloy is provided. According to still further aspects of the present invention, there is provided a soft magnetic film layer formed by using the above-described sputtering target. According to still further aspects of the present invention, a perpendicular magnetic recording medium having the above soft magnetic film layer is provided.

According to the present invention, it is possible to provide a soft magnetic alloy for a perpendicular magnetic recording medium which exhibits a low Bs at room temperature and a small decrease in Bs at a high temperature, and a sputtering target for a film for forming the alloy. material. By using the alloy of the present invention in the perpendicular magnetic recording medium to sufficiently exhibit the magnetic properties of the soft magnetic alloy, the function of the soft magnetic film layer can be sufficiently improved, and as a result, the performance of the perpendicular magnetic recording medium can be improved.

Hereinafter, the present invention will be described in detail. As long as it is not specifically stated, "%" is expressed as at% in this specification.

First, since the sputtering film is a thin film, the influence of the diamagnetic field on Hk is large, that is, the effect of demagnetization factor and magnetization intensity is expected to be high. Here, the demagnetization factor is an external factor determined by the shape of the film; the intensity of magnetization is equivalent to Bs of the soft magnetic film. Therefore, as described above, Hk is correlated with Bs of the soft magnetic film. However, in this regard, it is necessary to increase Bs for high Hk, and it is necessary to be the same as the conventional high-Bs soft magnetic alloy.

Here, a review was made to find factors affecting Hk in addition to Bs. In the examples and comparative examples described later, a sputtering film was formed on a certain soft magnetic amorphous alloy composition, and as a result of evaluating Hk, high Hk was obtained at a high Bs as previously considered, but in some cases It was found in the composition that Hk became extremely small. After the detailed analysis, it was revealed that Bs was almost zero in the temperature of the substrate particularly when the film was formed by sputtering, and Hk was extremely small as described above.

From the above, it is considered that the Bs at room temperature which is not the conventional one is important, and it is important to reduce the temperature of the Bs at the time of film formation from the room temperature. That is, the Bs applied at room temperature is low, but the temperature at the time of sputtering film formation is about 150 ° C, and the alloy having a small decrease in Bs from the room temperature suggests that it is possible to shrink while having a high Hk. "Infiltration". root According to this idea, when the Bs at room temperature is 0.3 to 1.2 T, it is lower than that of the conventional soft magnetic film, and the alloy having a small decrease in Bs at 150 ° C with respect to room temperature Bs is The present invention has been completed.

Further, as an index for measuring the decrease in Bs at 150 ° C with respect to Bs at room temperature, (Bs at 150 ° C) / (Bs at room temperature) × 100% was used. That is, when the Bs ratio is a value closer to 100%, the decrease in Bs due to an increase in temperature is smaller. Hereinafter, it is simply referred to as "Bs ratio".

The alloy of the present invention satisfies the mathematical formula (1): 0 ≦ Fe% / (Fe% + Co%) ≦ 0.5. The upper limit is more correctly 0.50. In the present alloy, Fe and Co are elements for maintaining the magnetization of the recording film to maintain the minimum necessary magnetization; the behavior of Bs and Fe%/(Fe%+Co%) is expressed in the so-called Sley Slater-Pauling curve, etc. The most important insight in the present invention is that it is found that a relatively high Bs soft magnetic film can also obtain a high Hk at room temperature as a high Bs ratio as described above, and further reduce Fe%/(Fe). %+Co%), found to be able to maintain a high Bs ratio.

The detailed reason for this phenomenon of the present alloy having an amorphous structure is unknown, but it is related to the orbital distribution of 3d electrons of Fe atoms and Co atoms. In particular, when Fe%/(Fe%+Co%) exceeds 0.5, a sufficient Bs ratio cannot be obtained. Further, generally, a thin Ru film is inserted between soft magnetic films in a perpendicular magnetic recording medium, and an antiferromagnetic coupling of a soft magnetic film and a Ru film is used, and there is a weak noise from the outside in a hard disk use environment. Magnetic field tolerance. Because there is the use of Fe to improve the antiferromagnetic couple In the case of a combination, it is preferable to contain a certain degree of Fe. However, it is better to reduce Fe because of the high Bs ratio. Therefore, the preferred range of Fe%/(Fe%+Co%) is more than 0% of 0.45% or less, more preferably 0.1% or more and 0.40% or less.

The alloy of the present invention satisfies the mathematical formula (2): 5≦Ti%+Zr%+Hf%+V%+Nb%+Ta%+B%/2. In the present alloy, Ti, Zr, Hf, V, Nb, Ta, and B are used to improve the amorphous property; when these total amounts are less than 5, sufficient amorphous properties cannot be obtained. Further, when a crystalline alloy is used, there is a fear of noise generated from a magnetic recording medium. However, B is an element having a particularly high amorphous promoting effect, and an effect similar to one-half of the other elements can be obtained. Therefore, in the total mathematical expression, B uses only a value of 1/2. In order to obtain sufficient amorphous properties, it is preferably 9% or more, and more preferably 13% or more.

The alloy of the present invention also satisfies the formula (3): 0.3 ≦ 0.813 × Fe% / (Fe% + Co%) - 0.062 × TNM + 1.751 ≦ 1.2. If the lower limit value and the upper limit value are more correct, they are 0.30 and 1.20, respectively. In the alloy, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Ni, Cu, Al, B, C, Si, P, Zn, Ga, Ge, Sn, either The element to make Bs lower. The Bs of the alloy system is approximately equal to "0.813 × Fe% / (Fe% + Co%) - 0.062 × TNM + 1.751". Further, this mathematical expression is obtained by using Fe%/(Fe%+Co%) and TNM in the examples described below in the range of 0≦Fe%/(Fe%+Co%)≦0.50. The result of multiple regression analysis is a mathematical formula obtained with a high correlation coefficient; the value of the mathematical formula is set in the range of 0.3 to 1.2. In the case of 0.3 to 1.2 T, a soft magnetic alloy having a relatively low Bs compared to the conventional soft magnetic film is obtained. However, if it is less than 0.3, sufficient Hk cannot be obtained. If it exceeds 1.2, the "bleeding" will become larger as in the case of the conventional high-Bs soft magnetic film. Further, the effect of reducing Bs due to B is because only about half of the other elements are used, so that only the value of 1/2 is calculated for TNM. Further, it is preferably 0.4 to 1.1, more preferably 0.5 to 1.0.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples.

Table 1 shows the alloy powder produced by the gas atomization method under the composition. The molten base material was 25 kg, which was inductively melted in a decompressed Ar ambient gas, and the alloy melt was poured out from a nozzle having a diameter of 8 mm, and then immediately sprayed with a high-pressure Ar gas for atomization. This powder was classified to 500 μm or less, and a raw material powder as HIP forming (heat grading) was used. The HIP forming material was prepared by filling a raw material powder into a carbon steel can having a diameter of 200 mm and a length of 100 mm, and then degassing and sealing by vacuum. The powder filled with the powder was subjected to HIP molding at a molding temperature of 1000 ° C, a pressure of 120 MPa, and a holding time of 2 hours. Thereafter, a sputtering target having a diameter of 95 mm and a thickness of 2 mm was prepared from the molding system. A film was produced using the sputtering target.

The chamber was evacuated to a volume of 1 × 10 ^-4 Pa or less, and Ar gas having a purity of 99.99% was placed at a pressure of 0.6 Pa to perform sputtering. The film was produced on the glass substrate at a thickness of 1.5 μm. Further, at the time of sputtering, the temperature of the substrate during film formation is about 150 ° C by irradiation with a plasma of a sputtering gas. Regarding the film sample, the Bs at room temperature (30 ° C) and 150 ° C was measured using a VSM (vibration sample magnetometer), and the percentage of Bs at 30 ° C relative to Bs at 150 ° C was evaluated (hereinafter, "Bs ratio" or "(Bs at 150 °C) / (Bs at 30 °C) × 100%")).

Further, for the film surface, the BH curves of the respective magnetizations in the vertical direction and the planar direction are also measured, and the difference of the applied magnetic field necessary for saturating the magnetization with respect to the respective directions, that is, from the vertical direction The necessary applied magnetic field subtracts the result of the necessary applied magnetic field in the planar direction as the biasing magnetic field Hk due to the magnetization direction. The crystal structure is evaluated by X-ray diffraction. The X-ray source was Cu-kα ray, and the scanning speed was 4°/min, and the measurement was performed. In the diffraction pattern, when the peak of the crystal is not seen, ○ is given, and when the peak of the crystal is seen, X is given to evaluate whether the crystal structure is appropriate or not.

As shown in Table 1, No. 1 to 22 are examples of the present invention, and Nos. 23 to 35 are comparative examples.

First, the value of the mathematical formula (3) "0.813 × Fe% / (Fe% + Co%) - 0.062 × TNM + 1.751" of the embodiment is consistently indicating that the Bs at room temperature is good, and the mathematical expression is effective. When the value of the mathematical formula is 0.3 to 1.2, it is lower than that of the conventional soft magnetic film, and it is confirmed that an alloy having a Bs of 0.3 to 1.2 T is obtained. Further, as in Comparative Examples No. 25 and 26, Fe%/(Fe%+Co%) is Large, the mathematical formula is not effective for compositions that depart from the scope of the invention.

Next, in the present invention Nos. 7 to 16, the Fe%/(Fe%+Co%) was fixed at 0.3, the TNM for lowering the Bs was changed to 13 to 27, and the Bs at room temperature was changed to 0.34. ~1.18 sample. The Hk of these samples was changed to Bs at the same time, and the Bs range which was lower than the conventional one was confirmed as compared with the conventional phenomenon of "high Hk at high Bs".

Here, the gist of the present invention will be described by way of the present invention and comparative examples. Inventive Examples Nos. 3, 5, 6, 12, 18, 21 and Comparative Examples Nos. 23 to 29 show that Bs, which is about 0.7 T at room temperature, is more than the conventional soft magnetic film. low. However, the Hk of the examples Nos. 3, 5, 6, 12, 18, and 21 of the present invention is 550 A/m or more, which is large, whereas the Hk of the comparative examples No. 23 to 29 is 90 A/m or less. , significantly lower, the Hk of Comparative Example No. 26, which is almost zero at 150 ° C, is extremely low.

Further, it was confirmed that the size of Hk of these samples was clearly inversely related to Fe%/(Fe%+Co%) and positively correlated with Bs ratio. Although the reason for this phenomenon is not conclusive, it is estimated that the film receives a magnetic field from the outside during sputtering, and therefore has a magnetization path that affects film formation at a temperature of about 150 ° C. In this way, in addition to the phenomenon of "high Hk obtained by high Bs", it has been found that "the high Hk is obtained as a large Bs ratio". Further, it is also understood that an alloy having a high Bs ratio is obtained in such a manner that Fe%/(Fe%+Co%) is set to be low.

Hereinafter, each comparative example will be described. Comparative Example No. 23~29, Regardless of which Fe%/(Fe%+Co%) exceeds 0.50, the Bs ratio is low and Hk is low. In Comparative Example No. 30 to 32, the total of the amorphous promoting elements was low, and the result of X-ray diffraction and the crystallization peak were confirmed. In Comparative Example No. 33, the Bs at room temperature was low, the Bs ratio was low, and Hk was low.

Further, the comparative examples Nos. 34 and 35 will be described in detail. The end portion of the rod-shaped ferrite magnet having a diameter of 1 mm and a length of 10 mm was brought into contact with the center of the film of the inventive examples Nos. 7, 10, 12 and Comparative Examples Nos. 34 and 35, and then removed. The position of the ferrite magnet was measured from the surface of the film of 10 mm, and the residual magnetization was measured by a gaussmeter. In this case, the residual magnetization of the inventive example No. 12 was 1.0, and the inventive example No. 10 was 1.2. Inventive Example No. 7 was 1.5, and Comparative Examples Nos. 34 and 35 were 2.5. As described above, Comparative Examples Nos. 34 and 35 showed that Bs at room temperature was high, and the magnetic field was affected in a wide range after the external magnetic field was removed, and the "bleeding" was large.

On the other hand, in the inventive examples Nos. 1 to 22, it is understood that the room temperature Bs is 0.3 to 1.2 T, which is lower than that of the conventional perpendicular magnetic recording medium, and Bs with respect to room temperature. The ratio of Bs at 150 ° C is high and has a high Hk.

Claims (6)

An alloy for a soft magnetic film layer in a perpendicular magnetic recording medium, the alloy being at%, comprising: one or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W , Mn, Ni, Cu, Al, B, C, Si, P, Zn, Ga, Ge, Sn; the remaining part Co, Fe; and, unavoidable impurities; all satisfy the following mathematical formula (1)~( 3): (1) 0≦Fe%/(Fe%+Co%)≦0.5(2)13≦Ti%+Zr%+Hf%+V%+Nb%+Ta%+B%/2(3) 0.3≦0.813×Fe%/(Fe%+Co%)−0.062×TNM+1.751≦1.2 (In the mathematical formula, Fe%/(Fe%+Co%) is the content of Fe and the total content of Fe and Co. Ratio; TNM is the total amount of addition of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Ni, Cu, Al, B, C, Si, P, Zn, Ga, Ge, and Sn. %, however, use B for only 1/2 times the value). A soft magnetic film layer comprising the alloy according to claim 1. A perpendicular magnetic recording medium having the soft magnetic film layer as recited in claim 1. A sputtering target comprising the alloy according to claim 1. A soft magnetic film layer formed by using a sputtering target as described in claim 4. A drooping of a soft magnetic film layer as recited in claim 5 Straight magnetic recording media.