FeCo alloy for soft magnetic layer of magnetic recording media

Abstract

To provide FeCo-based alloy and target material each having excellent corrosion resistance and sputtering property.SOLUTION: FeCo-based alloy for a soft magnetic layer includes TCR element and TAM element. The balance is Fe, Co and inevitable impurities. The content (at%) of each element satisfies formula (1) 0.1≤TCR≤10.0, formula (2) 11.0≤TAM≤25.0, formula (3) 16.0≤[TCR / 2+TAM]≤25.0, and formula (4) 0.20≤[Fe / (Fe+Co)]≤0.80. The FeCo-based alloy has microstructure that consisting of (Fe,CO) phases having Fe and / or Co as a main constituent, and intermetallic compound phases including TCR element or TAM element. In this microstructure, the number of (Fe,Co) phases in which the diameter of the minimum circumscribed circle surrounding the outside of the (Fe,Co) phase exceeds 30 μm is 0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to FeCo alloys. More specifically, this invention relates to FeCo alloys suitable for the soft magnetic layer of a magnetic recording medium. [Background technology]

[0002] In recent years, with the increasing capacity of magnetic recording media, the practical application of media employing perpendicular magnetic recording (perpendicular magnetic recording media) has been progressing. In perpendicular magnetic recording media, the easy magnetization axis is oriented perpendicular to the surface of the media in the magnetic film. This perpendicular magnetic recording media is suitable for high recording density.

[0003] A perpendicular magnetic recording medium has a magnetic recording layer and a soft magnetic layer. The perpendicular magnetic recording medium further has a seed layer, an undercoat layer, etc., between the magnetic recording layer and the soft magnetic layer.

[0004] The soft magnetic layer prevents the spread of magnetic flux generated from the head during recording, thereby ensuring a vertical magnetic field. From the perspective of increasing the recording density of magnetic recording media, there has been a demand for an amorphous soft magnetic layer with a high saturation magnetic flux density. FeCo alloys are known as materials for forming such a soft magnetic layer.

[0005] On the other hand, soft magnetic layers are also required to have high corrosion resistance depending on the application and operating environment of the magnetic recording medium. Japanese Patent Publication No. 2017-82330 (Patent Document 1) discloses an alloy for a soft magnetic film layer that has improved corrosion resistance without significantly reducing the saturation magnetic flux density, comprising one or more of Ge, Ru, Rh, Pd, Re, Os, Ir, and Pt, one or more of Sc, Y, lanthanides (atomic numbers 57 to 71), Ti, Zr, Hf, V, Nb, Ta, Mo, W, and B, with the remainder being Fe, Co, and unavoidable impurities, wherein the content of each element satisfies a predetermined relationship. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-82330 [Overview of the project] [Problems that the invention aims to solve]

[0007] Soft magnetic layers made of FeCo alloys are typically obtained by magnetron sputtering using a target material made of an FeCo alloy. When the target alloy has high magnetic properties, the discharge during sputtering becomes unstable, leading to a decrease in the productivity of the soft magnetic layer. This tendency is particularly pronounced when using thick target materials. A target material capable of efficiently producing a soft magnetic layer with high corrosion resistance, and a suitable FeCo alloy for this target material, have yet to be proposed.

[0008] The objective of the present invention is to provide an FeCo-based alloy that can produce a soft magnetic layer with excellent sputtering properties and high corrosion resistance, even in thick target materials. [Means for solving the problem]

[0009] The inventors observed that in an FeCo alloy having a predetermined composition, a microstructure is formed consisting of a (Fe,Co) phase mainly composed of Fe and Co, and a metal compound phase. They noted that the magnetic properties deteriorate when the (Fe,Co) phase, which is the magnetic layer, is separated by the metal compound phase containing non-magnetic metal elements. Through diligent research, the inventors discovered that by controlling this microstructure, stable sputtering becomes possible even for thick target materials, thus completing the present invention.

[0010] That is, the FeCo alloy for the soft magnetic layer of a magnetic recording medium according to one embodiment of the present invention contains one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W. The remainder is Fe, Co, and unavoidable impurities. In this FeCo alloy, the total content of TCR elements TCR (at%), the total content of TAM elements TAM (at%), and the content of Fe and Co (at%) all satisfy the following formulas (1)-(4). (1) 0.1 ≤ TCR ≤ 10.0 (2) 11.0 ≤ TAM ≤ 25.0 (3) 16.0 ≤ [TCR / 2 + TAM] ≤ 25.0 (4) 0.20 ≤ [Fe / (Fe+Co)] ≤ 0.80 Furthermore, this FeCo alloy has a microstructure formed from a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing TCR or TAM elements. In this microstructure, there are zero (Fe,Co) phases whose minimum circumscribed circle diameter surrounding the outside of the (Fe,Co) phase exceeds 30 μm.

[0011] Another embodiment of the present invention provides an FeCo alloy for the soft magnetic layer of a magnetic recording medium, comprising one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W. The remainder consists of Fe, Co, and unavoidable impurities. In this FeCo alloy, the total content of TCR elements (TCR(at%)), the total content of TAM elements (TAM(at%)), and the content of Fe and Co (at%) all satisfy the following formulas (1)-(4). (1) 0.1 ≤ TCR ≤ 10.0 (2) 11.0 ≤ TAM ≤ 25.0 (3) 16.0 ≤ [TCR / 2 + TAM] ≤ 25.0 (4) 0.20 ≤ [Fe / (Fe+Co)] ≤ 0.80 Furthermore, this FeCo alloy has a microstructure formed from a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing TCR or TAM elements. A randomly selected area of ​​this microstructure is 3250 μm². 2 Within the field of view, there are five or more (Fe,Co) phases in which the diameter of the largest inscribed circle that can be drawn inside the (Fe,Co) phase is 1.8 μm or more, and the diameter of the smallest circumscribed circle surrounding the outside of this phase is 30 μm or less.

[0012] From another perspective, the material of the sputtering target material for the soft magnetic layer of the magnetic recording medium according to the present invention is an FeCo alloy. This FeCo alloy contains one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W. The remainder is Fe, Co, and unavoidable impurities. In this FeCo alloy, the total content of TCR elements TCR (at%), the total content of TAM elements TAM (at%), and the content of Fe and Co (at%) all satisfy the following formulas (1)-(4). (1) 0.1 ≤ TCR ≤ 10.0 (2) 11.0 ≤ TAM ≤ 25.0 (3) 16.0 ≤ [TCR / 2 + TAM] ≤ 25.0 (4) 0.20 ≤ [Fe / (Fe+Co)] ≤ 0.80 Furthermore, this FeCo alloy has a microstructure formed from a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing TCR or TAM elements. In this microstructure, there are zero (Fe,Co) phases whose minimum circumscribed circle diameter surrounding the outside of the (Fe,Co) phase exceeds 30 μm.

[0013] According to another aspect, the material of the sputtering target material for the soft magnetic layer of the magnetic recording medium according to the present invention is a FeCo-based alloy. This FeCo-based alloy contains at least one TCR element selected from Ru and Re, and at least one TAM element selected from Zr, V, Nb, Ta, Mo, and W. The balance is Fe, Co, and inevitable impurities. In this FeCo-based alloy, the total content ratio TCR (at%) of the TCR elements, the total content ratio TAM (at%) of the TAM elements, and the content ratios (at%) of Fe and Co satisfy all of the following formulas (1)-(4). (1) 0.1 ≦ TCR ≦ 10.0 (2) 11.0 ≦ TAM ≦ 25.0 (3) 16.0 ≦ [TCR / 2 + TAM] ≦ 25.0 (4) 0.20 ≦ [Fe / (Fe + Co)] ≦ 0.80 Furthermore, this FeCo-based alloy has a microstructure formed from a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing a TCR element or a TAM element. In a randomly selected area of 3250 μm 2 in the field of view, the diameter of the largest inscribed circle that can be drawn inside the (Fe,Co) phase is 1.8 μm or more, and the number of (Fe,Co) phases where the diameter of the smallest circumscribed circle surrounding the outside of this phase is 30 μm or less is 5 or more.

Advantages of the Invention

[0014] [[ID=十八]] According to the FeCo-based alloy of the present invention, a target material with excellent sputtering properties can be obtained. The target material made of this FeCo-based alloy is suitable for manufacturing a soft magnetic layer with high corrosion resistance.

Brief Description of the Drawings

[0015] [Figure 1] FIG. ۱ is an example of a scanning electron microscope photograph showing the microstructure of the FeCo-based alloy according to Example (No. ۱) of the present application. [Figure 2] FIG. [Figure 3] Figure 3 is an explanatory diagram illustrating the state of the (Fe,Co) phase in the microstructure shown in Figure 1. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below based on preferred embodiments, with reference to drawings as appropriate. In this specification, "X~Y" indicating a range means "X or more and Y or less".

[0017] [FeCo alloy] The FeCo alloy for the soft magnetic layer of a magnetic recording medium according to the present invention contains one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W. The remainder consists of Fe, Co, and unavoidable impurities. This FeCo alloy has a component composition that satisfies the following formulas (1)-(4), and has a microstructure with an appropriate size and number of (Fe,Co) phases mainly composed of Fe and / or Co. The "(Fe,Co) phase mainly composed of Fe and / or Co" means a phase that is substantially formed from Fe or Co or both, with the content of other elements being negligible.

[0018] [(1) 0.1 ≤ TCR ≤ 10.0] This FeCo alloy has a total content of 0.1 at% to 10.0 at% of one or more TCR elements selected from Ru and Re. From the viewpoint of improving the corrosion resistance of the soft magnetic layer obtained by sputtering, the total content of TCR elements TCR(at%) is preferably 0.5 at% or more, more preferably 1.0 at% or more, and even more preferably 2.0 at% or more. From the viewpoint of not excessively reducing the saturation magnetic flux density Bs, the total content TCR(at%) is preferably 9.0 at% or less, more preferably 7.0 at% or less, and even more preferably 5.0 at% or less.

[0019] [(2) 11.0 ≤ TAM ≤ 25.0] This FeCo alloy has a total content of one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W of 11.0 at% to 25.0 at%. From the viewpoint of increasing the amorphous nature of the FeCo alloy and contributing to the formation of intermetallic compounds with Fe and / or Co, the total content of TAM elements TAM(at%) is preferably 12.0 at% or more, more preferably 13.5 at% or more, and even more preferably 15.0 at% or more. From the viewpoint of not excessively reducing the saturation magnetic flux density Bs, the alloy content TAM(at%) is preferably 23.0 at% or less, more preferably 21.0 at% or less, and even more preferably 20.0 at% or less.

[0020] [(3)16.0≦[TCR / 2+TAM]≦25.0] TCR and TAM elements are non-magnetic metallic elements, and both can contribute to a decrease in saturation magnetic flux density Bs. By controlling the value [TCR / 2+TAM], calculated from the total content of TCR elements (TCR) and the total content of TAM elements (TAM), to between 16.0 at% and 25.0 at%, the magnetic properties required for the soft magnetic layer of a magnetic recording medium can be secured. From the viewpoint of obtaining an appropriate saturation magnetic flux density Bs, the value [TCR / 2+TAM] is preferably 17.0 at% or higher, and more preferably 18.0 at% or higher. From the viewpoint of preventing an excessive decrease in saturation magnetic flux density Bs, the value [TCR / 2+TAM] is preferably 23.0 at% or lower, and more preferably 20.0 at% or lower.

[0021] [(4)0.20≦[Fe / (Fe+Co)]≦0.80] The main components of FeCo alloys are Fe and Co. Soft magnetic layers formed with Fe and Co as the main components exhibit excellent saturation magnetic flux density Bs. Here, "main component" means that the total content of Fe and Co is at least 50 at%. From the viewpoint of obtaining a soft magnetic layer suitable for magnetic recording media, the ratio of the Fe content (at%) to the total Fe and Co content (at%) [Fe / (Fe+Co)] is 0.20 to 0.80, preferably 0.30 to 0.70, and more preferably 0.40 to 0.65.

[0022] [Microorganisms] The FeCo alloy according to the present invention contains Fe, Co, TCR elements, and TAM elements in the aforementioned component composition, and also has a microstructure in which the size and number of the magnetic phase (Fe,Co) phases are controlled. This microstructure reduces the magnetic properties of the FeCo alloy to an appropriate range, enabling stable sputtering even with thick target materials. Furthermore, the ability to use thick target materials improves the production efficiency of the soft magnetic layer, and as a result, the productivity of magnetic recording media is improved.

[0023] Specifically, the microstructure of this FeCo alloy is formed from a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing TCR elements or TAM elements. In this specification, "intermetallic compound phase containing TCR elements or TAM elements" means the intermetallic compound phase formed by the reaction of TCR elements or TAM elements with Fe and / or Co, regardless of their ratio.

[0024] When observing the microstructure of this FeCo alloy using a scanning electron microscope (SEM), a randomly selected area of ​​3250 μm² was observed. 2Within the field of view, there are five or more (Fe,Co) phases whose maximum inscribed circle diameter is 1.8 μm or more, and whose minimum circumscribed circle diameter is 30 μm or less. Here, "five or more (Fe,Co) phases whose maximum inscribed circle diameter is 1.8 μm or more, and whose minimum circumscribed circle diameter is 30 μm or less" means, in other words, that in this microstructure, many of the magnetic (Fe,Co) phases are fragmented, and the microstructure is controlled to suppress networking by the same phase. Suppression of (Fe,Co) phase networking means that, relatively speaking, networking of the non-magnetic intermetallic compound phase progresses, promoting fragmentation of the (Fe,Co) phase by the intermetallic compound phase, and as a result, the total length of the (Fe,Co) phase network becomes shorter. The total area of ​​the formed (Fe,Co) phase is determined by the alloy composition; therefore, if the total length of the (Fe,Co) phase network is shortened, its width will increase. This means that the number of (Fe,Co) phases with a small minimum circumcircle diameter and a large maximum incircle diameter increases.

[0025] From another perspective, when the microstructure of the FeCo alloy according to the present invention is observed using a scanning electron microscope (SEM), the number of (Fe,Co) phases whose minimum circumscribed circle diameter surrounding it exceeds 30 μm is zero. Here, "the number of (Fe,Co) phases whose minimum circumscribed circle diameter surrounding it exceeds 30 μm is zero" means, in other words, that in this microstructure, the (Fe,Co) phase is separated by the intermetallic compound phase, and as a result, excessive networking of the (Fe,Co) phase is suppressed.

[0026] Here, the "largest inscribed circle" is defined as the largest circle in diameter among the hypothetical circles contained within the (Fe,Co) phase, which is inscribed in the contour of the (Fe,Co) phase at at least two points and can be drawn without intersecting this contour. The "smallest circumscribed circle" is defined as the smallest circle in diameter among the hypothetical circles that can contain the (Fe,Co) phase, which is circumscribed around the contour of the (Fe,Co) phase at at least two points and can be drawn without intersecting this contour.

[0027] The microstructure of the FeCo alloy according to the present invention will be specifically described below with reference to the scanning electron microscope image in Figure 3. In Figure 3, the black areas are the (Fe,Co) phase mainly composed of Fe and / or Co, and the white areas are the intermetallic compound phase containing TCR elements or TAM elements. For example, (Fe,Co) phase B and (Fe,Co) phase C are separated by the intermetallic compound phase. In other words, (Fe,Co) phase B and (Fe,Co) phase C are not networked. Also, in Figure 3, the dashed circle indicated by reference numeral 1 is the maximum inscribed circle of (Fe,Co) phase A, and the dotted dashed circle indicated by reference numeral 2 is the minimum circumscribed circle of (Fe,Co) phase A. The diameter of the maximum inscribed circle drawn inside (Fe,Co) phase A is 1.8 μm or more, and the diameter of the minimum circumscribed circle surrounding the outside of (Fe,Co) phase A is 30 μm or less. This (Fe,Co) phase A is partially networked, but the network is controlled to prevent it from becoming excessive. (Figure 3 shows an area of ​​3250 μm²) 2 Within this field of view, the number N of (Fe,Co) phases that "can draw a maximum inscribed circle with a diameter of 1.8 μm or more inside, and whose minimum circumscribed circle surrounding it has a diameter of 30 μm or less" is recognized as being 5 or more. Furthermore, in the microstructure of Figure 3, there are no (Fe,Co) phases with a minimum circumscribed circle diameter exceeding 30 μm. In other words, in this microstructure, the networking of the magnetic (Fe,Co) phase is suppressed.

[0028] In target materials with a microstructure in which a network of (Fe,Co) phases is formed, the (Fe,Co) phase network acts like a magnetic circuit, improving soft magnetic properties within the target material (i.e., within the FeCo alloy) and reducing PTF (Pass Through Flux). This makes it difficult to achieve stable discharge during magnetron sputtering, and sputtering tends to be difficult. In contrast, with an area of ​​3250 μm²... 2 In a microstructure where the maximum inscribed circle diameter drawn within it is 1.8 μm or more, and the minimum circumscribed circle diameter surrounding it is 30 μm or less, and where there are 5 or more (Fe,Co) phases, and where there are 0 (Fe,Co) phases whose minimum circumscribed circle diameter is greater than 30 μm, even with relatively high Fe and Co content, the (Fe,Co) phases are prevented from being connected in a network-like manner, and the non-magnetic intermetallic compound phase is prevented from being separated by the (Fe,Co) phase. In a target material having such a microstructure, an excessive increase in magnetic performance is suppressed, and the discharge stability during sputtering is improved. From this viewpoint, an area of ​​3250 μm² 2 In the field of view, the number of (Fe,Co) phases that can draw a maximum inscribed circle with a diameter of 1.8 μm or more inside them, and whose minimum circumscribed circle surrounding them has a diameter of 30 μm or less, is preferably 6 or more, more preferably 8 or more, and even more preferably 10 or more.

[0029] In this specification, "the number of (Fe,Co) phases in which a maximum inscribed circle with a diameter of 1.8 μm or more can be drawn inside, and the minimum circumscribed circle surrounding it has a diameter of 30 μm or less" is determined by SEM observation of the test specimen, with a field of view of 3250 μm. 2To achieve this, for example, a field of view of 50 μm vertically and 65 μm horizontally is randomly selected, and the (Fe,Co) phases whose maximum inscribed circle diameter is 1.8 μm or more and whose minimum circumscribed circle diameter is 30 μm or less are counted. Furthermore, "the number of (Fe,Co) phases whose minimum circumscribed circle diameter surrounding it exceeds 30 μm" can be determined by counting the (Fe,Co) phases in the obtained SEM image whose minimum circumscribed circle diameter exceeds 30 μm. Note that the diameter of the maximum inscribed circle that can be drawn inside a (Fe,Co) phase and the diameter of the minimum circumscribed circle surrounding it are measured by image processing of the SEM image. Commercially available image analysis software can be used for image processing.

[0030] [Sputtering target material] The material of the sputtering target material according to the present invention is an FeCo-based alloy having the aforementioned component composition and microstructure. This target material is suitable for manufacturing the soft magnetic layer of a magnetic recording medium.

[0031] This target material can be obtained, for example, by forming a molded body from alloy powder raw material using HIP (hot isostatic pressing), and then processing this molded body into an appropriate shape using mechanical means. The preferred pressure for HIP forming is 90 to 150 MPa, and the preferred temperature is 1000 to 1200°C.

[0032] The FeCo-based alloy powder according to the present invention can be obtained by atomization. Gas atomization is preferred. This alloy powder is then subjected to classification as needed (for example, sieving classification using a sieve with a mesh size of 300 μm). The resulting powder can be used in HIP molding.

[0033] Preferably, the target material is obtained using alloy powder with an average particle diameter of 10 μm or more and 80 μm or less as a raw material. In alloy powders with an average particle diameter of less than 10 μm, the oxygen content in the outer periphery increases. Therefore, the generation of particles due to oxides tends to increase during sputtering. From the viewpoint of reducing particle generation, more preferably, the target material is obtained using alloy powder adjusted to an average particle diameter of 15 μm or more, and even more preferably, 20 μm or more as a raw material. Furthermore, in target materials obtained using alloy powder with an average particle diameter exceeding 80 μm, the size of the (Fe,Co) phase formed in the microstructure becomes smaller, which may reduce the magnetic performance. From this viewpoint, more preferably, the target material is obtained using alloy powder adjusted to an average particle diameter of 70 μm or less, and even more preferably, 60 μm or less as a raw material.

[0034] In this specification, unless otherwise specified, "average particle size" refers to the particle size D50 (median diameter) at the point where the cumulative volume reaches 50% in a volume-based cumulative curve obtained by laser diffraction scattering. The average particle size D50 of FeCo-based alloy powder is measured, for example, by a commercially available laser diffraction-scattering particle size distribution analyzer. In this apparatus, the alloy powder is flowed into the cell together with pure water, and a cumulative curve is created based on the light scattering information of the resulting particles, thereby determining the average particle size D50. An example of such an apparatus is Nikkiso's "Microtrac MT3000". [Examples]

[0035] The effects of the present invention will be demonstrated below by the examples, but the present invention should not be interpreted restrictively based on the description of these examples. Unless otherwise specified, the test temperature was room temperature (25°C ± 5°C) for all tests.

[0036] [Manufacturing of raw material powders] Each raw material was weighed to achieve the composition shown in Table 1-2, placed in a crucible made of refractory material, and melted by induction heating under reduced pressure in an Ar gas atmosphere or a vacuum atmosphere. The molten metal was then allowed to flow out through a small hole (8 mm in diameter) provided at the bottom of the crucible, and gas atomization was performed using high-pressure Ar gas to obtain the FeCo-based alloy powders of Examples No. 1-13 and Comparative Examples No. 14-21.

[0037] [Manufacturing of sputtering target materials] FeCo-based alloy powders from Examples No. 1-13 and Comparative Examples No. 14-21 were subjected to HIP molding (hot isostatic pressing) according to the following procedure to produce sputtering target materials.

[0038] First, the obtained alloy powder was classified using a sieve with a mesh size of 300 μm. The average particle size (median diameter) of the classified alloy powder was measured using the method described above, and the results are shown in Table 1-2 below.

[0039] Next, the powder after sieving classification was filled into a carbon steel can (120 mm in diameter, 20 mm in length), degassed under vacuum, and then sintered using a HIP (High-Intensity Pressurization) apparatus at a temperature of 1000-1200°C, a pressure of 90-150 MPa, and a holding time of 5-10 hours to produce a sintered body. This sintered body was then processed by wire cutting, turning, and surface grinding to produce a disc-shaped sputtering target material with a diameter of 95 mm and a thickness of 5 mm.

[0040] [Scanning electron microscope observation] Test specimens were taken from target materials No. 1-21, and the cross-sections of each specimen were polished. The cross-sections of each specimen were observed using a scanning electron microscope (SEM), measuring 50 μm in length and 65 μm in width (area 3250 μm²). 2) The area was randomly selected and photographed in 10 fields of view. Then, image analysis was performed to measure the diameter of the largest inscribed circle and the diameter of the smallest circumscribed circle drawn on the (Fe, Co) phase, and the number of (Fe, Co) phases that could draw the largest inscribed circle with a diameter of 1.8 μm or more and the diameter of the smallest circumscribed circle was 30 μm or less was recorded. The average value of the numerical values measured in 10 fields of view is shown in Table 1-2 below as the number N1. Similarly, the number of (Fe, Co) phases with a diameter of the smallest circumscribed circle exceeding 30 μm was recorded. The results measured in 10 fields of view are shown in Table 1-2 below as the number N2.

[0041] SEM images obtained for the target materials of No.1 and No.18 are shown in Fig.1 and Fig.2 respectively. In the figures, the black portions indicated by arrows are the (Fe, Co) phases, and the white portions are the intermetallic compound phases containing TCR elements or TAM elements. As shown in Fig.1, in the microstructure of No.1 which is an example, there are (Fe, Co) phases inside that can draw the largest inscribed circle with a diameter of 1.8 μm or more and the diameter of the smallest circumscribed circle surrounding it is 30 μm or less, and in the field of view of an area of 3250 μm 2 , 5 or more can be confirmed. Also, in the microstructure of No.1, it was confirmed that there is no (Fe, Co) phase with a diameter of the smallest circumscribed circle exceeding 30 μm, and the networking of the (Fe, Co) phase is suppressed. On the other hand, as shown in Fig.2, in the microstructure of No.18 which is a comparative example, a plurality of (Fe, Co) phases having the smallest circumscribed circle with a diameter exceeding 30 μm were confirmed. Also, in the microstructure of No.18, the number N1 of (Fe.Co) phases with a diameter of the largest inscribed circle of 1.8 μm or more and a diameter of the smallest circumscribed circle of 30 μm or less was less than 5.

[0042] [Sputtering property evaluation] Using the obtained target materials No.1-21 (thickness 5 mm), sputtering was performed by DC magnetron sputtering under the following conditions, and the stability of the discharge state was evaluated. The evaluation results are shown in Table 1-2 below. In the table, those with stable discharge are shown as A, those with unstable discharge are shown as B, and those without discharge are shown as C. Substrate: Glass substrate (thickness 1 mm) Chamber atmosphere: Argon gas (99.99% purity) Chamber pressure: 0.6 Pa

[0043] [Physical properties of alloy thin films] The saturation magnetic flux density Bs(T), amorphousness, and corrosion resistance of alloy thin films (500 nm thick) prepared by sputtering under the aforementioned conditions were evaluated. For samples No. 14, 15, and 18-21, which exhibited unstable discharge (evaluation: B) or no discharge (evaluation: C), the target material thickness was changed to 2 mm, and sputtering was performed to create and evaluate alloy thin films (500 nm thick). Details of each evaluation method are as follows.

[0044] [Saturated magnetic flux density Bs] Using a VSM (vibrating sample magnetometer), the saturation magnetic flux density Bs at room temperature was measured with an applied magnetic field of 1200 kA / m. The sample volume required to calculate the saturation magnetic flux density Bs was determined from the area of ​​the alloy thin film and its thickness, which was determined by transmission electron microscopy (TEM) observation. The results are shown in Table 1-2 below.

[0045] [Amorphous] A thin alloy film was attached to a glass plate using double-sided tape, and a diffraction pattern was obtained using an X-ray diffractometer. The diffraction conditions were as follows: X-ray source: Cu-Kα ray Scan speed: 4° / min In the X-ray diffraction patterns of amorphous materials, no diffraction peaks are observed, and a halo pattern characteristic of amorphous materials is obtained. In the X-ray diffraction patterns of incomplete amorphous materials, diffraction peaks are observed, but their height is lower compared to the diffraction peaks of crystalline materials, and a halo pattern is also visible. Therefore, a ranking was performed based on the following criteria. The results are shown in Table 1-2 below. A: A halo pattern can be seen. C: No halo pattern visible

[0046] [Corrosion resistance] The alloy thin film after sputtering was cut into 10 × 25 mm sections on each glass substrate and immersed in 10 ml of 10% by mass nitric acid solution. After 60 minutes of immersion, the nitric acid solution was collected and used as the test solution. The Fe and Co ion content in the test solution was quantified using an inductively coupled plasma (ICP) emission spectrometer. The elution amount (mg / l) calculated by dividing the total amount of Fe and Co ions obtained by the volume of the test solution is shown in Table 1-2 below.

[0047] [Table 1]

[0048] [Table 2]

[0049] Table 1, Nos. 1-13, represents the FeCo alloys of the examples, and Table 2, Nos. 14-21, represents the FeCo alloys of the comparative examples. As shown in Table 1, the FeCo alloys of the examples enabled stable sputtering using a 5 mm thick target material, and a thin alloy film that can serve as a soft magnetic layer with excellent corrosion resistance was obtained.

[0050] In contrast, No. 14 does not contain TCR elements, has a low value [TCR / 2 + TAM], has a small number of (Fe,Co) phases of a predetermined size N1, and a large number of (Fe,Co) phases N2 that are extensively networked. As a result, No. 14 has a high saturation magnetic flux density Bs, making sputtering on a 5 mm thick target material unstable, and the resulting alloy thin film has poor amorphous properties and corrosion resistance.

[0051] No. 15 has a low TAM element content, a low [TCR / 2+TAM] value, a low number of (Fe,Co) phases of a predetermined size N1, and a high number of large networked (Fe,Co) phases N2. As a result, No. 15 has a high saturation magnetic flux density Bs, making sputtering on a 5mm thick target material unstable, and the resulting alloy thin film has poor amorphous properties.

[0052] In No. 16, the excess TCR element resulted in a high value [TCR / 2+TAM], leading to an alloy thin film with an excessively low saturation magnetic flux density Bs. Similarly, in No. 17, the excess TAM element resulted in a high value [TCR / 2+TAM], also leading to an alloy thin film with an excessively low saturation magnetic flux density Bs.

[0053] Although No. 18-20 had an appropriate component composition, it could not discharge on a 5mm thick target material because the number of (Fe,Co) phases of the specified size N1 was small and the number of large networked (Fe,Co) phases N2 was large. In No. 21, the high Fe content resulted in a low saturation magnetic flux density Bs, and because the number of (Fe,Co) phases of the specified size N1 was small and the number of large networked (Fe,Co) phases N2 was large, stable sputtering could not be achieved.

[0054] As shown in Tables 1 and 2, a soft magnetic layer with excellent properties can be obtained from the FeCo-based alloy according to the present invention. The advantages of the present invention are clear from these evaluation results. [Industrial applicability]

[0055] The FeCo alloys described above are suitable for the soft magnetic layer of various magnetic recording media. [Explanation of symbols]

[0056] 1. Largest inscribed circle 2. Smallest circumscribed circle

Claims

1. It comprises one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W, with the remainder being Fe, Co, and unavoidable impurities. The total content of the above TCR elements TCR (at%), the total content of the above TAM elements TAM (at%), and the content of Fe and Co (at%) all satisfy the following formulas (1)-(4): (1) 0.1 ≤ TCR ≤ 10.0 (2) 11.0 ≤ TAM ≤ 25.0 (3) 16.0≦[TCR / 2+TAM]≦25.0 (4) 0.20≦[Fe / (Fe+Co)]≦0.80 It has a microstructure consisting of a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing the above TCR element or the above TAM element. In the above microstructure, the number of (Fe,Co) phases where the diameter of the smallest circumscribed circle surrounding the outside of the (Fe,Co) phase exceeds 30 μm is zero, an FeCo-based alloy for the soft magnetic layer of a magnetic recording medium.

2. It comprises one or more TCR elements selected from Ru and Re, and one or more TAM elements selected from Zr, V, Nb, Ta, Mo, and W, with the remainder being Fe, Co, and unavoidable impurities. The total content of the above TCR elements TCR (at%), the total content of the above TAM elements TAM (at%), and the content of Fe and Co (at%) all satisfy the following formulas (1)-(4): (1) 0.1 ≤ TCR ≤ 10.0 (2) 11.0 ≤ TAM ≤ 25.0 (3) 16.0≦[TCR / 2+TAM]≦25.0 (4) 0.20≦[Fe / (Fe+Co)]≦0.80 It has a microstructure consisting of a (Fe,Co) phase mainly composed of Fe and / or Co, and an intermetallic compound phase containing the above TCR element or the above TAM element. In the above microstructure, the number of (Fe,Co) phases whose minimum circumscribed circle diameter surrounding the outside of the (Fe,Co) phase exceeds 30 μm is zero. A randomly selected area of ​​the above microstructure: 3250 μm ２ An FeCo alloy for the soft magnetic layer of a magnetic recording medium, wherein, within the field of view, the maximum inscribed circle diameter that can be drawn inside the (Fe,Co) phase is 1.8 μm or more, and the minimum circumscribed circle diameter surrounding the outside of that phase is 30 μm or less, and there are 5 or more (Fe,Co) phases.

3. A sputtering target material for the soft magnetic layer of a magnetic recording medium, wherein the material is the FeCo-based alloy described in claim 1 or 2.

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