TW201726945A - Non-magnetic amorphous alloy, and sputtering target material and magnetic recording medium using said alloy - Google Patents

Abstract

The purpose of the present invention is to provide: a non-magnetic amorphous Co alloy that can prevent the occurrence of crystallization during high-temperature treatment (for example, heat treatment at approximately 400-500 DEG C during magnetic layer formation on a heat-assisted magnetic recording medium); and a sputtering target material and a magnetic recording medium that use the Co alloy. In order to fulfill this purpose, the present invention provides a non-magnetic amorphous alloy that includes: 0 at% to 2 at% inclusive of Fe; 5 at% to 20 at% inclusive of an A group element comprising one or more elements selected from Ti, Zr, and Hf; 16 at% to 50 at% inclusive of a B group element comprising two or more elements selected from Cr, Mo, and W; 0 at% to 25 at% inclusive of a C group element comprising one or more elements selected from V, Nb, and Ta; 0 at% to 20 at% inclusive of a D group element comprising one or more elements selected from Si, Ge, P, B, and C; and a remainder which comprises Co and unavoidable impurities. The sum of the content of the A group element and the content of the B group element is more than 35 at% to 70 at%.

Description

Non-magnetic and amorphous alloy, and sputtering target and magnetic recording medium using the same [Relationship between related applications]

Priority is claimed on the basis of Japanese Patent Application No. 2015-164493, the entire disclosure of which is hereby incorporated by reference.

The present invention relates to a non-magnetic and amorphous Co-based alloy and a sputtering target and a magnetic recording medium using the Co-based alloy.

In recent years, advances in magnetic recording technology have been remarkable. In order to increase the capacity of hard disk drives, the high recording density of magnetic recording media has been evolving, and it is currently being studied to achieve higher recording than conventional magnetic recording media. Heat-Assisted Magnetic Recording (Heat-Assisted Magnetic Recording).

The heat-assisted magnetic recording method is a method of recording data while heating a magnetic recording medium with a laser. As magnetic recording media evolves toward higher density, the problem of thermal fluctuations becomes significant. That is, the magnetically recorded data will disappear due to the influence of the surrounding heat. In order to avoid the problem of this thermal disturbance, it is necessary to increase the coercivity of the magnetic material used in the recording medium, but if the coercivity becomes too high, it becomes impossible to record. The way to solve this problem is the heat assisted magnetic recording method.

In the heat-assisted magnetic recording method, since the coercivity can be greatly reduced by heating the magnetic recording medium, a material having a high magnetic crystal eccentricity constant Ku can be used as the magnetic layer material of the magnetic recording medium. As the high Ku magnetic material, an ordered alloy such as an L1 ₀ type FePt alloy, an L1 ₀ type CoPt alloy, or an L1 ₁ type CoPt alloy is known. These magnetic materials are composed of an irregular phase of a face centered cubic (fcc) structure, for example, in a state in which a film is formed by a sputtering method, and the magnetic crystal anisotropy is extremely small. Therefore, in order to improve the magnetic crystal anisotropy, it is necessary to treat the disordered alloy film after film formation at a high temperature to be transformed into a L1 ₀ regular phase. Japanese Patent Publication No. 2014-220029 (Patent Document 1) discloses that the heating temperature at the time of forming a magnetic layer can be reduced to about 400 to 500 ° C by adding Ag, Au, Cu, Ni or the like.

As a magnetic recording medium (heat assisted magnetic recording medium) of the heat assisted magnetic recording method, a magnetic recording medium having a nonmagnetic and amorphous layer is known.

For example, Japanese Laid-Open Patent Publication No. 2013-157071 (Patent Document 2) discloses a heat-assisted magnetic recording medium comprising a substrate, a base layer, and a magnetic layer containing an alloy having an L1 ₀ structure as a main component. The underlayer of Patent Document 2 is composed of, for example, a first underlayer composed of a non-magnetic and amorphous alloy such as NiTa, NiTi, CoTa, CoTi, CrTa, CrTi, CoCrZr, or CoCrTa. And the second underlayer is composed of an alloy having a BCC structure mainly composed of Cr; and the third underlayer is composed of an alloy having a BCC structure having a lattice constant of 2.98A or more; and a fourth underlayer , made up of MgO.

Further, Japanese Laid-Open Patent Publication No. 2012-174321 (Patent Document 3) discloses a heat-assisted magnetic recording medium including a non-magnetic substrate, a heat dissipation layer, a buffer layer, a soft magnetic substrate layer, and a magnetic recording layer. . The buffer layer of Patent Document 3 is composed of a non-magnetic and amorphous alloy such as CrTi, CrZr, CrTa, CrW or the like.

Further, Japanese Laid-Open Patent Publication No. 2011-146089 (Patent Document 4) discloses a heat-assisted magnetic recording medium comprising a substrate, a seed layer made of an amorphous ceramic (for example, SiO ₂ ), and An alignment control layer of crystallinity (for example, MgO) and a magnetic layer made of a material mainly composed of an FePt alloy.

The non-magnetic and amorphous layer (especially the alloy layer) contained in the magnetic recording medium of the heat-assisted magnetic recording method may be crystallized due to high-temperature treatment at the time of formation of the magnetic layer.

On the other hand, Ogsha Publishing, 1982, P94 (Non-Patent Document 1) discloses an amorphous alloy which exhibits a crystallization temperature of about 800K.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2014-220029

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2013-157071

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2012-174321

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2011-146089

[Non-patent literature]

[Non-Patent Document 1] Addition to the book "The Foundation of Amorphous Metals" by Ohmsha, 1982, P94

It is an object of the present invention to provide a non-magnetic and amorphous Co-based alloy capable of preventing crystallization from occurring during high-temperature treatment (for example, heat treatment at a temperature of 400 to 500 ° C in the formation of a magnetic layer of a heat-assisted magnetic recording medium). And a sputtering target and a magnetic recording medium using the Co-based alloy.

In order to solve the above problems, the present invention provides the following invention.

[1] An alloy containing at least 0 at% and not more than 2 at% of Fe, and 5 at% or more and 20 at% or less of Group A elements composed of one or more elements selected from Ti, Zr, and Hf. a group B element composed of two or more elements selected from Cr, Mo, and W at 16 at% or more and 50 at% or less, and one or two selected from V, Nb, and Ta at 0 at% or more and 25 at% or less. a group C element composed of the above elements and a group D element of 0 at% or more and 20 at% or less of one or more elements selected from Si, Ge, P, B, and C, and the remainder a non-magnetic and amorphous alloy composed of Co and unavoidable impurities, characterized by The sum of the content of the group A element and the content of the group B element is more than 35 at% and 70 at% or less.

[2] The alloy according to [1], wherein the content of the group C element is 1 at% or more and 25 at% or less.

[3] The alloy according to [1] or [2], wherein the content of the group D element is 5 at% or more and 20 at% or less.

[4] The alloy according to any one of [1] to [3] wherein the crystallization temperature is 773 K or more.

[5] A sputtering target comprising the alloy according to any one of [1] to [4].

[6] A magnetic recording medium comprising an alloy layer containing the alloy according to any one of [1] to [4].

According to the present invention, there is provided a process at a high temperature (for example, 400 to 500 ° C when a magnetic layer of a heat assisted magnetic recording medium is formed) A non-magnetic and amorphous Co-based alloy capable of preventing crystallization from occurring, and a sputtering target and a magnetic recording medium using the Co-based alloy.

Hereinafter, the present invention will be described in detail.

The alloy of the present invention is a non-magnetic and amorphous Co-based alloy satisfying the following composition.

(1) Content of Fe: 0 at% or more and 2 at% or less

(2) The content of the group A element: 5 at% or more and 20 at% or less

(3) The content of the B group element: 16 at% or more and 50 at% or less

(4) The sum of the content of the group A element and the content of the group B element: more than 35 at% and 70 at% or less

(5) The content of the C group element: 0 at% or more and 25 at% or less

(6) The content of the D group element: 0 at% or more and 20 at% or less

The alloy of the invention is non-magnetic. The term "non-magnetic" as used in the present invention means that the saturation magnetic flux density measured by applying a magnetic field of 1200 kA/m using a vibrating sample magnetometer (VSM) is less than 0.3T.

The alloy of the present invention is amorphous. The alloy of the present invention is amorphous, and thus the X-ray diffraction pattern exhibits a halo pattern.

The crystallization temperature of the alloy of the present invention is preferably 773 K or more, more preferably 873 K or more. The alloy of the present invention is amorphous and crystallizes upon heating. The temperature at which the amorphous alloy of the present invention is crystallized is "crystallization temperature". When the amorphous alloy is crystallized, an exothermic reaction occurs. The crystallization temperature was evaluated by measuring the temperature at which heat was released accompanying crystallization. For example, the crystallization temperature can be evaluated by differential scanning calorimetry (DSC) at a heating rate of 0.67 Ks ^-1 .

Hereinafter, the reason for limiting the composition in the alloy of the present invention will be described.

(1) Content of Fe: 0 at% or more and 2 at% or less

Fe is mainly an element for realizing cost reduction in a Co-based alloy, and is an optional component of the alloy of the present invention. The content of Fe is 0 at% or more and 2 at% or less based on the total number of atoms contained in the alloy of the present invention. When the content of Fe exceeds 2 at%, the amorphous alloy (amorphous) and non-magnetization of the Co-based alloy cannot be achieved, and therefore the Fe content is adjusted to 2 at% or less (including 0). When the alloy of the present invention contains Fe, the content of Fe can be appropriately adjusted within a range exceeding 0 at% and 2 at% or less.

(2) The content of the group A element: 5 at% or more and 20 at% or less

The group A element is composed of one or two or more elements selected from Ti, Zr, and Hf. The group A element is mainly an element for realizing amorphization (amorphization) in a Co-based alloy, and is an essential component of the alloy of the present invention. The content of the group A element is 5 at% or more and 20 at% or less, preferably 6 at% or more and 15 at% or less, more preferably 9 at% or more and 14 at% based on the total number of atoms contained in the alloy of the present invention. the following. In the case where the group A element is composed of one element, "the In the case where the group A element is composed of two or more elements, the "content of the group A element" means the total content of the two or more elements. When the content of the group A element is less than 5 at%, the alloying of the Co-based alloy cannot be achieved (amorphization), and therefore the content of the group A element is adjusted to 5 at% or more, preferably 6 at% or more. More preferably, it is 9 at% or more. In addition, when the content of the group A element exceeds 20 at%, the alloying of the Co-based alloy cannot be achieved (amorphization), and therefore the content of the group A element is adjusted to 20 at% or less, preferably 15 at%. The following is more preferably 14 at% or less.

(3) The content of the B group element: 16 at% or more and 50 at% or less

The group B element is composed of two or more elements selected from Cr, Mo, and W. The group B element is mainly an element for realizing the high temperature of the crystallization temperature of the Co-based amorphous alloy, and is an essential component of the alloy of the present invention. When one element selected from Cr, Mo, and W is used alone, the Co-based alloy cannot be amorphized (amorphous), and thus two or more elements selected from Cr, Mo, and W are used. The content of the group B element is 16 at% or more and 50 at% or less, preferably 16 at% or more and 40 at% or less based on the total number of atoms contained in the alloy of the present invention. The "content of the group B element" means the total content of two or more elements constituting the group B element. When the content of the group B element is less than 16 at%, the non-magnetization of the Co-based alloy cannot be achieved, and therefore the content of the group B element is adjusted to 16 at% or more. In addition, when the content of the group B element exceeds 50 at%, the amorphous phase of the Co-based alloy cannot be achieved (undefined Since the content of the group B element is adjusted to 50 at% or less, preferably 40 at% or less.

(4) The sum of the content of the group A element and the content of the group B element: more than 35 at% and 70 at% or less

The sum of the content of the group A element and the content of the group B element is more than 35 at% or more and 70 at% or less, preferably 36 at% or more and 65 at% or less based on the total number of atoms contained in the alloy of the present invention. More preferably, it is 37 at% or more and 64 at% or less. When the sum of the content of the group A element and the content of the group B element is 35 at% or less, the non-magnetization of the Co-based alloy cannot be achieved, and therefore the sum of the content of the group A element and the content of the group B element is It is adjusted to more than 35 at%, preferably 36 at% or more, and more preferably 37 at% or more. In addition, when the sum of the content of the group A element and the content of the group B element exceeds 70 at%, the amorphous phase (amorphization) of the Co-based alloy cannot be achieved, and therefore the content of the group A element and the group B element are not obtained. The sum of the contents is adjusted to 70 at% or less, preferably 65 at% or less, more preferably 64 at% or less.

(5) The content of the C group element: 0 at% or more and 25 at% or less

The group C element is composed of one or two or more elements selected from V, Nb, and Ta. The group C element is mainly an element for promoting the amorphization (amorphization) of the Co-based alloy and the high temperature of the crystallization temperature of the Co-based amorphous alloy, and is an optional component of the alloy of the present invention. The content of the group C element is 0 at% or more and 25 at% or less, preferably 0 at% or more based on the total number of atoms contained in the alloy of the present invention. 20 at% or less, more preferably 0 at% or more and 10 at% or less. When the C group element is composed of one element, the "content of the C group element" means the content of the one element, and when the C group element is composed of two or more types of elements, "C The content of the group element means the total content of the two or more elements. When the content of the group C element exceeds 25 at%, the amorphous phase of the Co-based alloy cannot be achieved. Therefore, the content of the group C element is adjusted to 25 at% or less, preferably 20 at% or less, and more preferably 10 at%. the following. When the alloy of the present invention contains a group C element, the content of the group C element can be appropriately adjusted within a range of more than 0 at% and 25 at% or less. The content of the group C element is, for example, 1 at% or more, 3 at% or more, or 4 at% or more.

(6) The content of the D group element: 0 at% or more and 20 at% or less

The group D element is composed of one or two or more elements selected from Si, Ge, P, B, and C. The group D element is mainly an element for improving the amorphous (amorphous) in the Co-based alloy, and is an optional component of the alloy of the present invention. The content of the group D element is 0 at% or more and 20 at% or less, preferably 0 at% or more and 15 at% or less, more preferably 0 at% or more and 10 at% based on the total number of atoms contained in the alloy of the present invention. the following. When the D group element is composed of one type of element, the "content of the D group element" means the content of the one element, and when the D group element is composed of two or more elements, "D" The content of the group element means the total content of the two or more elements. When the content of the D group element exceeds 20 at%, the amorphous phase of the Co-based alloy cannot be achieved (amorphous) Therefore, the content of the D group element is adjusted to 20 at% or less, preferably 15 at% or less, and more preferably 10 at% or less. When the alloy of the present invention contains a group D element, the content of the group D element can be appropriately adjusted within a range exceeding 0 at% and 20 at% or less. The content of the D group element is, for example, 5 at% or more.

In the alloy of the present invention, the remainder other than the Fe, the group A element, the group B element, the group C element, and the group D element is composed of Co and unavoidable impurities. Examples of the unavoidable impurities include Al, Cu, Mn, and the like. The content of the unavoidable impurities is preferably 1000 ppm or less.

The sputtering target of the present invention contains the alloy of the present invention. The sputtering target of the present invention can be used to form an alloy layer (alloy film) containing the alloy of the present invention.

The magnetic recording medium of the present invention comprises an alloy layer (alloy film) containing the alloy of the present invention. The magnetic recording medium of the present invention is, for example, a perpendicular magnetic recording medium, a heat assisted magnetic recording medium or the like. The alloy layer (alloy film) containing the alloy of the present invention can be formed by a sputtering method using a sputtering target containing the alloy of the present invention.

The alloy of the present invention can prevent crystallization from occurring during high-temperature treatment (for example, heat treatment at a temperature of 400 to 500 ° C in the formation of a magnetic layer of a heat-assisted magnetic recording medium). Therefore, the alloy of the present invention is suitable as a material which requires a non-magnetic and amorphous alloy layer among the alloy layers provided in a magnetic recording medium (for example, a heat-assisted magnetic recording medium) which is required to be processed at a high temperature.

Examples of the magnetic recording medium having a non-magnetic and amorphous layer include a substrate, a plurality of underlayers including a non-magnetic and amorphous underlayer, and a structure having an L1 ₀ structure. A heat-assisted magnetic recording medium having a magnetic layer as a main component (for example, JP-A-2013-157071); a non-magnetic substrate, a heat dissipation layer, a non-magnetic and amorphous buffer layer, and a soft layer are sequentially provided; A magnetically-assisted magnetic recording medium having a magnetic substrate layer and a magnetic recording layer (for example, JP-A-2012-174321); a substrate, a non-magnetic and amorphous seed layer, and crystallinity (for example, MgO) are sequentially provided. A heat-assisted magnetic recording medium having a magnetic layer composed of a material containing a FePt alloy as a main component (for example, JP-A-2011-146089). As the alloy of the present invention, a material which is a layer of these nonmagnetic and amorphous layers can be used.

[Examples]

Hereinafter, the present invention will be specifically described based on examples.

Generally, a film in a perpendicular magnetic recording medium is obtained by sputtering a sputtering target having the same composition as that of a composition, and forming a film on a glass substrate or the like. Here, the film formed by sputtering is quenched. On the other hand, as the test pieces of the examples and the comparative examples, a quenched ribbon produced by a single-roll type liquid rapid cooling device was used. This is an effect on the properties due to the composition of the film which is actually formed by sputtering and being quenched, and is easily evaluated by a liquid quenched ribbon.

[ conditions for the production of quenched ribbons]

30g of raw materials obtained by weighing the ingredients shown in Tables 1 and 2, In a water-cooled copper mold having a diameter of about 10 × 40 mm, it was subjected to arc melting in a reduced pressure Ar to prepare a molten base material for the quenched ribbon. The production conditions of the quenched ribbon are as follows. The molten base material was placed in a quartz tube having a diameter of 15 mm in a single roll manner, and the diameter of the soup nozzle was set to 1 mm, the ambient air pressure was 61 kPa, the spray differential pressure was 69 kPa, and the number of revolutions of the copper roll (diameter 300 mm) was 3000 rpm. The soup was placed at a pitch of 0.3 mm. The temperature of the soup is set as the moment after the melting of the molten base material is melted and dropped. The quenched ribbon thus produced was used as a test material, and the following items were evaluated.

[Evaluation of saturation flux density of quenched ribbons]

The saturation magnetic flux density was measured by a VSM device (vibration sample magnetometer) at an applied magnetic field of 1200 kA/m. The weight of the test material is set to about 15 mg. In Tables 1 and 2, the test material of the saturation magnetic flux density of less than 0.3 T is set to "A", and the test material of 0.3T or more is set to "C".

[Structure of quenched ribbon]

In general, when an X-ray diffraction pattern of an amorphous material is measured, a diffraction peak is not observed, and an amorphous specific halo pattern is obtained. Further, in the case where it is not completely amorphous, although a diffraction peak is observed, the peak height thereof becomes lower as compared with the crystalline material, and a halo pattern is also seen. For this reason, the amorphous property was evaluated by the following method.

[Evaluation of Amorphousness]

Attach the test material to the glass plate with double-sided tape and apply X-ray diffraction Set the diffraction pattern. At this time, the test material was attached so that the measurement surface became the contact surface of the copper roll of the quenched ribbon. The X-ray source was a Cu-α line and was measured at a scanning speed of 4°/min. In Tables 1 and 2, in the diffraction pattern, the test material which can confirm the halo pattern is set to "A", and the test material which does not see the halo pattern at all is set to "C".

[Evaluation of crystallization temperature of quenched ribbon]

Usually, an amorphous material causes crystallization with heating, and a temperature at which crystallization occurs is referred to as a crystallization temperature. In addition, an exothermic reaction occurs during crystallization. The crystallization temperature was evaluated by measuring the temperature at which heat was released accompanying crystallization. For this reason, the crystallization temperature was evaluated in the following manner. It was investigated by differential scanning calorimetry (DSC) under the conditions of a heating rate of 0.67 Ks ^-1 . In Tables 1 and 2, the test materials for the crystallization temperature of 873 K or higher are set to "A", and the test materials of crystallization temperature of 773 K or more and less than 873 are set to "B", and the crystallization temperature is less than 773 K. The test material is ordered as "C".

In Tables 1 and 2, Nos. 1 to 36 are examples of the invention, and Nos. 37 to 46 are comparative examples.

As shown in Tables 1 and 2, in Examples Nos. 1 to 36 of the present invention, the evaluation of the saturation magnetic flux density, the amorphous property, and the crystallization temperature was "A" or "B" for the Co-based alloy satisfying the following composition. "."

(1) Content of Fe: 0 at% or more and 2 at% or less

(2) The content of the group A element: 5 at% or more and 20 at% or less

(3) The content of the B group element: 16 at% or more and 50 at% or less

(4) The sum of the content of the group A element and the content of the group B element: more than 35 at% and 70 at% or less

(5) The content of the C group element: 0 at% or more and 25 at% or less

(6) The content of the D group element: 0 at% or more and 20 at% or less

In Comparative Example No. 37, the content of the Group B element was less than 16 at%, and the sum of the content of the Group A element and the content of the Group B element was 35 at% or less. In Comparative Example No. 38, since the element constituting the group B element was of one type, it was not amorphous, and the crystallization temperature was also low. In Comparative Example No. 39, since the content of the Group A element exceeded 20 at%, it was not amorphous, and the crystallization temperature was also low. In Comparative Example No. 40, since the content of the group A element was less than 5 at%, it was not amorphous and the crystallization temperature was also low. In Comparative Example No. 41, since the content of the Group B element exceeded 50 at%, it was not amorphous, and the crystallization temperature was also low. In Comparative Examples Nos. 42 and 43, since the content of the Group C element exceeded 25 at%, it was not amorphous, and the crystallization temperature was also low. In Comparative Examples Nos. 44 and 45, since the content of the group D element exceeded 20 at%, it was not amorphous, and the crystallization temperature was also low. ratio In Comparative Example No. 46, since the Fe content exceeds 2 at%, it is not nonmagnetic and amorphous, and the crystallization temperature is also low.

Next, a method of manufacturing a sputtering target is disclosed. The compositional compositions of Nos. 1, No. 10, No. 15, No. 25, No. 30 of Table 1 and Comparative Examples No. 37 and No. 45 of Table 2 were used to weigh the melting raw materials. After being inductively heated and melted in a refractory crucible in a decompressed Ar gas atmosphere, the soup was discharged by a nozzle having a diameter of 8 mm in the lower part of the crucible, and was atomized by Ar gas. This gas atomized powder was used as a raw material, and degassed into an SC tank having an outer diameter of 220 mm, an inner diameter of 210 mm, and a length of 200 mm. The degree of vacuum arrival at the time of degassing is set to be about 1.3 × 10 ^-2 Pa.

The above-mentioned powder-filled bridle was heated to 1,150 ° C, and then placed in a restrictive container having a diameter of 230 mm, and molded at a pressure of 500 MPa. The cured molded body produced by the above method was processed into a disk shape having a diameter of 180 mm and a thickness of 7 mm by wire cutting, lathe processing, and surface polishing, and used as a sputtering target.

For the seven types of component compositions, a sputter film was formed on the glass substrate using a sputtering target. The magnetic flux density, the amorphous property, and the crystallization temperature of the sputtered film were the same as those of Tables 1 and 2 in any of the compositions.

As described above, according to the present invention, a non-magnetic and amorphous (amorphous) Co-based alloy having a sufficiently high crystallization temperature and a sputtering target using the Co-based alloy are provided. And magnetic recording media.

Claims (6)

An alloy containing 0 at% or more and 2 at% or less of Fe, 5 at% or more and 20 at% or less of Group A elements composed of one or more elements selected from Ti, Zr, and Hf, 16 at% or more a group B element composed of two or more elements selected from Cr, Mo, and W at 50 at% or less, and one or two or more elements selected from V, Nb, and Ta at 0 at% or more and 25 at% or less. The group C element and the group D element composed of one or two or more elements selected from Si, Ge, P, B, and C, which are 0 at% or more and 20 at% or less, and the remainder are Co and A non-magnetic and amorphous alloy which is composed of impurities and which is characterized in that the sum of the content of the group A element and the content of the group B element is more than 35 at% and not more than 70 at%. The alloy according to claim 1, wherein the content of the group C element is 1 at% or more and 25 at% or less. The alloy according to claim 1, wherein the content of the group D element is 5 at% or more and 20 at% or less. The alloy according to claim 1, wherein the crystallization temperature is 773 K or more. A sputtering target comprising an alloy as described in claim 1 of the patent application. A magnetic recording medium comprising an alloy layer containing an alloy as described in claim 1 of the patent application.