TW202006149A - Ni-based alloy for seed layer in magnetic recording medium - Google Patents

Abstract

In order to provide a Ni-based alloy for a seed layer, the alloy enabling achievement of a seed layer that exhibits enhanced alignment to the (111) plane and that has a fine crystal grain size, a sputtering target which contains said alloy, and a magnetic recording medium having a seed layer which contains said alloy, provided is a Ni-based alloy for a seed layer in a magnetic recording medium, the alloy containing one or more types of elements RE selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, wherein the content rate of said elements RE falls within 1-10 at%.

Description

Ni-based alloy for seed layer of magnetic recording media

The present invention relates to a Ni-based alloy for a seed layer of a magnetic recording medium, a sputtering target containing the alloy, and a magnetic recording medium having a seed layer containing the alloy.

For magnetic recording media, large capacity is important. In order to achieve a large capacity, it is necessary to increase the recording density.

Media systems using longitudinal magnetic recording have been popularized. In recent years, in place of this medium, a medium employing a perpendicular magnetic recording (perpendicular magnetic recording) system (perpendicular magnetic recording medium) is becoming popular. In a perpendicular magnetic recording medium, the easy axis of magnetization is aligned in the perpendicular direction to the medium surface in the magnetic film. This perpendicular magnetic recording medium is suitable for high recording density.

The perpendicular magnetic recording medium has a magnetic recording layer and a soft magnetic layer. The perpendicular magnetic recording medium further has a seed layer, a base film layer, etc. between the magnetic recording layer and the soft magnetic layer.

Japanese Patent Laid-Open No. 2009-155722 discloses a seed layer composed of a NiW-based alloy. This seed layer can contribute to the miniaturization of the magnetic recording layer.

Japanese Unexamined Patent Publication No. 2012-128933 discloses a target for a seed layer whose material is Ni-Fe-Co-M alloy. The alloy contains elements W, Mo, Ta, Cr, V or Nb as element M. This target system contributes to the alignment of the seed layer to the (111) plane.

Japanese Unexamined Patent Publication No. 2017-191625 discloses that the material is a target for the seed layer of Ni-Fe-Co-M alloy. The alloy contains noble metals (Au, Ag, Pd, Rh, Ir, Ru, Re or Pt) as element M. This target system contributes to the alignment of the seed layer to the (111) plane.

Japanese Unexamined Patent Publication No. 2013-073635 discloses the addition of rare earth alloys as materials for sputtering targets. From this target, a soft magnetic layer of a perpendicular magnetic recording medium is formed. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2009-155722 [Patent Document 2] Japanese Unexamined Patent Publication No. 2012-128933 [Patent Document 3] Japanese Patent Application Publication No. 2017-191625 [Patent Document 4] Japanese Patent Application Publication No. 2013-073635

[Problems to be solved by the invention]

For magnetic recording media, there is a requirement for higher recording density. There is room for improvement in the orientation of the seed layer to the (111) plane and the refinement of crystal grains.

An object of the present invention is to provide a Ni-based alloy for a seed layer that can obtain a seed layer with high alignment to the (111) plane and a fine crystal grain size, a sputtering target containing the alloy, and a seed crystal containing the alloy Layer of magnetic recording media. [Means to solve the problem]

The Ni-based alloy for the seed layer of the magnetic recording medium of the present invention (hereinafter also referred to as "Ni-based alloy of the present invention") contains a material selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy , Ho, Er, Tm, Yb, and Lu, a group of one or more elements RE. The content rate of the element RE in the Ni-based alloy of the present invention is 1 at% or more and 10 at% or less.

In the Ni-based alloy of the present invention, Ni content rate: Fe content rate: Co content rate = α: β: γ represents Ni content rate (at%), Fe content rate (at%) and Co When the content ratio (at%) is (but, α+β+γ=100), it is preferable that α is 15 or more and 100 or less, β is 0 or more and 60 or less, and γ is 0 or more and 70 or less.

The Ni-based alloy of the present invention preferably further contains Fe and/or Co.

The Ni-based alloy of the present invention preferably further contains one or more elements M1 selected from the group consisting of Ru, Re, W, Mo, and Ta. The content rate of the element M1 in the Ni-based alloy of the present invention is preferably 25 at% or less.

The Ni-based alloy of the present invention preferably further contains one or more elements M2 selected from the group consisting of Al, Si, B, and C. The content of M2 in the Ni-based alloy of the present invention is preferably 10 at% or less.

According to another aspect, the sputtering target of the present invention is composed of the Ni-based alloy of the present invention. That is, the material of the sputtering target of the present invention is the Ni-based alloy of the present invention. The Ni-based alloy of the present invention contains one or more kinds selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu The element RE. The content rate of the element RE in the Ni-based alloy of the present invention is 1 at% or more and 10 at% or less.

Furthermore, according to still another aspect, the magnetic recording medium of the present invention has a seed layer containing the Ni-based alloy of the present invention. The seed layer is preferably obtained by sputtering using the sputtering target of the present invention. The material of the target of the present invention is preferably the Ni-based alloy of the present invention. The Ni-based alloy of the present invention contains one or more kinds selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu The element RE. The content rate of the element RE in the Ni-based alloy of the present invention is 1 at% or more and 10 at% or less. [Effect of invention]

With the Ni-based alloy of the present invention, a seed layer with high alignment to the (111) plane and a fine crystal grain size can be obtained. The Ni-based alloy of the present invention can contribute to the high recording density of magnetic memory media.

[Forms for carrying out the invention]

The Ni-based alloy for the seed layer of the magnetic recording medium of the present invention includes: (1) Ni, and (2) One or more element RE selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The content rate of the element RE in the Ni-based alloy of the present invention is 1 at% or more and 10 at% or less. In addition, when the Ni-based alloy of the present invention contains two or more kinds of element RE, the "content rate of element RE" means the total content of the two or more kinds of element RE.

In a preferred aspect, the composition of the Ni-based alloy of the present invention is 1 or more elements RE: 1at% or more and 10at% or less, and Ni and inevitable impurities: the rest.

La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu (that is, element RE) are all rare earth elements. Ni has an fcc structure. The mechanism of the element RE system is not clear, but the priority alignment of the fcc structure can be changed from (200) to (111). A seed layer excellent in alignment to the (111) plane can be obtained from an alloy in which element RE is added to Ni. With this seed layer, a high recording density in perpendicular magnetic recording media can be achieved.

The solid solution range of element RE to Ni is very narrow. Therefore, in the seed layer obtained from the alloy in which the element RE is added to Ni, intermetallic compounds are precipitated. By this precipitation, the crystal grain size becomes finer. With this seed layer, a high recording density in a perpendicular magnetic recording medium can be achieved.

From the viewpoint of high recording density, the content rate of the element RE in the Ni-based alloy of the present invention is preferably 1 at% or more, and more preferably 2 at% or more. The excess element RE system shifts the seed layer to a structure other than the fcc structure. From the viewpoint that the seed layer can maintain the fcc structure, the content rate of the element RE is preferably 10 at% or less, and more preferably 5 at% or less.

The Ni-based alloy of the present invention may further contain Fe and/or Co. The Ni-based alloy of the present invention includes a state in which neither Fe nor Co is contained, a state in which Fe is contained but not in Co, a state in which Co is contained but not in Fe, and a state in which both Fe and Co are contained.

In the Ni-based alloy of the present invention, the ratio of the Ni content rate (at%), Fe content rate (at%) and Co content rate (at%) is based on the Ni content rate: Fe content rate: Co The content rate = a: β: γ said. Also, α+β+r=100. α is the percentage of Ni content (at%) relative to the total content (at%) of Ni, Fe and Co, and β is the Fe content relative to the total content (at%) of Ni, Fe and Co The percentage of the content rate (at%), γ is the percentage of the content rate of Co (at%) relative to the total content rate (at%) of Ni, Fe and Co.

α is preferably 15 or more and 100 or less. With a Ni-based alloy having α of 15 or more, a seed layer with suppressed coercive force can be obtained. From the same point of view, α is more preferably 20 or more, particularly preferably 25 or more, even more preferably 30 or more, particularly preferably 40 or more, still more preferably 50 or more, and particularly preferably 60 or more.

β is preferably 0 or more and 60 or less. With β-based Ni-based alloys within this range, a seed layer with suppressed coercive force can be obtained. From the same viewpoint, β is more preferably 2 or more, particularly preferably 5 or more, and even more preferably 10 or more. From the same viewpoint, β is more preferably 50 or less, and particularly preferably 40 or less.

γ is preferably 0 or more and 70 or less. With a Ni-based alloy in which γ is within this range, a seed layer with suppressed coercivity in the (111) direction can be obtained. From the same viewpoint, γ is more preferably 2 or more, particularly preferably 5 or more, and even more preferably 10 or more. From the same viewpoint, γ is more preferably 60 or less, particularly preferably 40 or less, and even more preferably 30 or less.

When the Ni-based alloy of the present invention contains Fe but does not contain Co, it is preferable that α is 40 or more and less than 100, and β is more than 0 and 60 or less. Also, at this time, γ is 0.

When the Ni-based alloy of the present invention contains Co but does not contain Fe, it is preferable that α is 30 or more and less than 100, and γ is more than 0 and 70 or less. Also, β is 0 at this time.

When the Ni-based alloy of the present invention contains Fe and Co, it is preferable that α is 15 or more and not more than 100, β exceeds 0 and 60 or less, and γ exceeds 0 and 70 or less.

In a preferred aspect, the composition of the Ni-based alloy of the present invention is 1 or more elements RE: 1at% or more and 10at% or less, and Ni, and Fe and/or Co, and inevitable impurities: the remainder.

The Ni-based alloy of the present invention may further contain one or more elements M1 selected from the group consisting of Ru, Re, W, Mo, and Ta. A seed layer excellent in alignment to the (111) plane can be obtained from the Ni-based alloy containing the element M1. Furthermore, a seed layer with a fine crystal grain size can be obtained from a Ni-based alloy containing the element M1. With this seed layer, a high recording density in perpendicular magnetic recording media can be achieved.

From the viewpoint of high recording density, the content of the element M1 is preferably 1 at% or more, and particularly preferably 2 at% or more. The excessive element M1 shifts the seed layer to a structure other than the fcc structure. Furthermore, the excessive element M1 may cause amorphization of the seed layer. From the viewpoint that the seed layer can maintain the fcc structure and from the viewpoint that the amorphization is unlikely to occur, the content of the element M1 is preferably 20 at% or less, and particularly preferably 10 at% or less. In addition, when the Ni-based alloy of the present invention contains two or more elements M1, the "content rate of element M1" means the total content rate of the two or more elements M1.

In a preferred aspect, the composition of the Ni-based alloy of the present invention is 1 or more element RE: 1at% or more and 10at% or less, One or more elements M1: 20at% or less, and Ni, and Fe and/or Co, and inevitable impurities: the remainder.

The Ni-based alloy of the present invention may further contain one or more elements M2 selected from the group consisting of Al, Si, B, and C. A seed layer with excellent alignment to the (111) plane can be obtained from a Ni-based alloy containing the element M2. Furthermore, a seed layer with a fine crystal grain size can be obtained from a Ni-based alloy containing the element M2. With this seed layer, a high recording density in perpendicular magnetic recording media can be achieved.

From the viewpoint of high recording density, the content of the element M2 is preferably 1 at% or more, and particularly preferably 2 at% or more. The excessive element M2 may cause amorphization of the seed layer. From the viewpoint of not easily causing amorphization of the seed layer, the content rate of the element M2 is preferably 5 at% or less. In addition, when the Ni-based alloy of the present invention contains two or more elements M2, the "content rate of element M2" means the total content rate of the two or more elements M2.

From the viewpoint of achieving a high recording density in the perpendicular magnetic recording medium, the total content of the element M1 and the content of the element M2 is preferably 1 at% or more, and particularly preferably 2 at% or more. From the viewpoint of not easily causing amorphization of the seed layer, the total content of the element M1 and the content of the element M2 is preferably 20 at% or less, and particularly preferably 15 at% or less.

In a preferred aspect, the composition of the Ni-based alloy of the present invention is 1 or more element RE: 1at% or more and 10at% or less, 1 or more elements M1: 20at% or less, One or more than two elements M2: 5at% or less, and Ni, and Fe and/or Co, and inevitable impurities: the remainder.

In another preferred aspect, the composition of the Ni-based alloy of the present invention is 1 or more element RE: 1at% or more and 10at% or less, One or more than two elements M2: 5at% or less, and Ni, and Fe and/or Co, and inevitable impurities: the remainder.

The powder composed of the Ni-based alloy of the present invention can be obtained by atomization. The preferred atomization is gas atomization. The powder is classified as necessary (for example, particles with a particle diameter of 500 μm or less are extracted). The powder after classification is filled in a can made of carbon steel. The tank is vacuum degassed and sealed to obtain billets. In this small embryo, HIP forming (hot pressure equalization) was applied. The preferred pressure for HIP forming is 50 MPa or more and 300 MPa or less, and the preferred sintering temperature is 800°C or more and 1350°C or less. By HIP molding, a molded body is obtained. This shaped body is processed to obtain a target. By applying sputtering to this target, a seed layer having the same composition as that of this target is obtained. This seed layer is incorporated in the magnetic recording medium. [Example]

Hereinafter, the effects of the present invention will be clarified by examples, but based on the description of the examples, the present invention should be interpreted without limitation.

As described above, the seed layer is formed by sputtering a target having the same composition as its composition. This seed layer is obtained by rapid cooling and solidification. In the formation of the seed layer, since a large amount of labor is required, the test piece obtained by the single-roll method is used. The single-roll method has the same steps as rapid cooling and solidification like sputtering. By using the single roll method, the evaluation of the film to be obtained by sputtering can be easily performed.

30 g of raw materials weighed with the composition shown in Table 1-5 below are put into a water-cooled copper casting mold with a diameter of 10 mm and a length of 40 mm. The mold was depressurized, and arc melting was performed in an argon atmosphere to obtain a molten base material. This base material was put into a quartz tank with a diameter of 15 mm, and the liquid was discharged from the nozzle, and the test piece was obtained by the single-roll method. The conditions of this single roll method are as follows. Outlet nozzle diameter: 1mm Ambient air pressure: 61kPa Spray differential pressure: 69kPa Roller material: copper Roller diameter: 300mm Rotation speed of roller: 3000rpm Clearance between roller and discharge nozzle: 0.3mm

In addition, the rest of the alloys other than the RE element, M1 element, and M2 element described in each table are Ni-Fe-Co and inevitable impurities. In addition, Tables 1 to 4 are examples, and Table 5 is comparative examples.

[Crystal size] The microstructure image of the cross section of the test piece in the roll direction is obtained. The crystal grain size was measured in accordance with the "JIS G 0551" "Microscope Test Method for Steel and Crystal Particle Size". The rating is based on the following criteria. A: P/Lt is 1.5 or more B: P/Lt is 1.2 or more and less than 1.5 C: P/Lt is less than 1.2

The results of the crystal particle size are shown in Table 1-5 below.

[Coercivity] Attach the test piece to the sample table with double-sided tape. Under the condition of an initial external magnetic field of 144 kA/m, the coercive force was measured with a vibrating sample type coercive force meter. The rating is based on the following criteria. A: The coercive force is below 300A/m B: The coercive force exceeds 300A/m and is below 500A/m C: coercive force exceeds 500A/m

The results of coercive force are shown in Table 1-5 below.

[Alignment] The test piece was attached to the glass plate with a double-sided tape so that the measurement surface became the contact surface with the copper roller. An X-ray diffraction device was used to obtain the diffraction pattern of the test piece. The conditions of diffraction are as follows. X-ray source: Cu-α line Scanning rate: 4°/min

Using the obtained diffraction pattern, find the intensity ratio I(111) of the X-ray intensity diffracted on the (111) plane to the X-ray intensity I(200) diffracted on the (200) plane. 111)/I(200).

The rating is based on the following criteria. A: Intensity ratio I(111)/I(200) is 1.0 or more B: The intensity ratio I(111)/I(200) is 0.7 or more and less than 1.0 C: The intensity ratio I(111)/I(200) is less than 0.7

In addition, the test piece does not retain the fcc structure and the amorphous one is also regarded as C.

The results of alignment are shown in Table 1-5 below.

As shown in Tables 1-5, with the Ni-based alloy of the present invention, seed layers with excellent properties can be obtained. According to this evaluation result, the advantage of the present invention is obvious. [Industry use possibility]

The Ni-based alloy described above is suitable for seed layers of various magnetic recording media.

Claims (8)

A Ni-based alloy for the seed layer of a magnetic recording medium, which contains a group selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu 1 or more elements RE of the group, The content rate of the aforementioned element RE is 1 at% or more and 10 at% or less. The Ni-based alloy of claim 1 further contains Fe and/or Co. The Ni-based alloy according to claim 1 or 2, wherein Ni content rate: Fe content rate: Co content rate = α: β: γ represents the Ni content rate (at%), Fe in the aforementioned Ni system alloy When the ratio of the content ratio (at%) to the Co content ratio (at%) (but, α+β+γ=100), α is 15 or more and 100 or less, β is 0 or more and 60 or less, and γ is 0 or more 70 the following. The Ni-based alloy according to any one of claims 1 to 3, further containing one or more elements M1 selected from the group consisting of Ru, Re, W, Mo, and Ta, The content rate of the aforementioned element M1 is 25 at% or less. The Ni-based alloy according to any one of claims 1 to 4, which further contains one or more elements M2 selected from the group consisting of Al, Si, B, and C, The content rate of the aforementioned element M2 is 10 at% or less. A sputtering target material composed of the Ni-based alloy according to any one of claims 1 to 5. A magnetic recording medium, which is a magnetic recording medium with a seed layer, The aforementioned seed layer contains the Ni-based alloy according to any one of claims 1 to 5. The magnetic recording medium of claim 7, wherein the aforementioned seed layer is obtained by sputtering using the sputtering target of claim 6.