JP3167808B2 - Soft magnetic thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic material, and more particularly to a soft magnetic thin film used for a magnetic head and an inductor suitable for high-density recording.

[0002]

2. Description of the Related Art In the field of magnetic recording, a magnetic recording medium having a high coercive force Hc is used as the magnetic recording density increases. In this case, in order to perform good magnetic recording, it is necessary to generate a high-density magnetic flux from the magnetic head. Therefore, as a soft magnetic thin film for a magnetic head, the saturation magnetic flux density Bs
, A low magnetostriction, a low coercive force Hc, and a high magnetic permeability μ are required. Similar magnetic properties are also required for inductors.

[0003] Under such circumstances, various soft magnetic thin films (about 15 kG or more) having a high saturation magnetic flux density have been proposed, but are not yet sufficient. An Fe—Co alloy system is known as a system having a higher saturation magnetic flux density than Fe. However, the material of this system has a large magnetostriction constant, and the coercive force Hc is 5 Oe even under manufacturing conditions in which the substrate temperature and annealing are optimized.
Because of the above, it was not sufficiently softened (Yoichi Hoshi et al., Journal of the Japan Society of Applied Magnetics, Vol. 10, N.
o. 2, P315 (1986)). It has been reported that rare earth metal elements control magnetostriction in Fe-Co-Sm obtained by further adding Sm to an alloy of this type (Shima et al., Abstracts of Spring Meeting of the Japan Institute of Metals (1992), P196).
However, the coercive force is at least 4 Oe and does not show sufficient soft magnetic properties. Furthermore, rare earth elements Dy other than Sm,
Magnetostriction control by addition of Ho and Tm has also been reported,
Its soft magnetic properties are not sufficient.

[0004] In order to improve the soft magnetic properties of Fe-based soft magnetic materials, Fe-MX-based alloys have been proposed (Japanese Patent Laid-Open Publication No. Hei 3 (1994)).
-153851). Here, M contains Co and X contains nitrogen. However, the obtained coercive force is 5 Oe or more (Table 1 of the publication), and softening is not sufficient.

As another technique for improving the soft magnetic properties of an Fe-based soft magnetic material, it has been proposed to incorporate N and O in Fe in an amount of several percent or less in Fe (Japanese Patent Application Laid-Open No. 2-57665).
issue). The obtained coercive force is 1.5 Oe or less, and the saturation magnetic flux density is excellent at 15 kG or more. However, this type of soft magnetic material has the disadvantage that oxidation proceeds easily at ambient temperature and humidity, and magnetic properties are greatly reduced. There is also a problem with heat resistance.

[0006]

Accordingly, an object of the present invention is to reduce the coercive force Hc, improve the magnetic permeability μ, and improve the corrosion resistance of a soft magnetic thin film made of an Fe—Co alloy. It is to make it.

[0007]

According to the present invention, magnetostriction is controlled by adding a rare earth metal element R to an Fe-Co alloy, and crystal grains are refined by adding O and N to soft magnetic material. Was planned. R and O also have the effect of forming a compound to suppress the growth of crystal grains, thereby improving soft magnetic properties. Further, R also has an effect of improving the corrosion resistance of the Fe—Co alloy. More specifically, the present invention employs the formula Fe _100- α _- β _- γ _- δCoαRβNγOδ (where R is a rare earth metal element, 15.0 ≦ α ≦ 55.0 at% 0.1 ≦ β ≦ 5 (0.0at% 0.1 ≦ γ ≦ 20.0at% 0.1 ≦ δ ≦ 10.0at%) A soft magnetic thin film characterized by having a composition represented by the following formula: The soft magnetic thin film of the present invention has a high saturation magnetic flux density B _S (17 kG or more) specific to Fe—Co alloys, a low coercive force Hc, and a high magnetic permeability μ. It also has excellent corrosion resistance. This soft magnetic thin film can be used as a single layer, but if it is used by laminating it with a non-magnetic or other composition magnetic film, an excellent product with little loss, for example, a magnetic recording / reproducing head can be manufactured.

Next, the content and action of each component will be described. C
o improves the saturation magnetic flux density in the range of 15.0 to 55.0 at%. In particular, at 20 to 50 at%, the saturation magnetic flux density increases, and 17.5 while achieving low coercive force and high magnetic permeability.
２３23.5 kG can be maintained. The present inventors proposed a soft magnetic thin film having the above composition and containing no Co in Japanese Patent Application No. 2-287566 (filed on Oct. 25, 1990), while achieving a low coercive force and a high magnetic permeability. The saturation magnetic flux density that can be maintained was only about 15.5 to 19.0 kG, but the present invention has further improved this.

The rare earth metal element R is Y, lanthanide La ~
Lu and at least one rare earth metal element selected from actinides Ac to Lr. Among these, the elements that provide good magnetic properties are Y, Ho, Sm, Er, and Dy.
And Y, Ho, Sm, and Er are particularly preferable.

[0010] R is added in the range of 0.1 to 5.0 at%, more preferably in the range of 0.3 to 3.5 at%. The addition of R suppresses magnetostriction and improves the corrosion resistance of the manufactured soft magnetic thin film. Furthermore, the growth of crystal grains is suppressed by the generation of the RO compound, and the crystal is refined to improve the soft magnetic properties. If R is less than 0.1 at%, there is no sufficient effect for suppressing magnetostriction. If R exceeds 5 at%, the coercive force exceeds 2.0 Oe and the soft magnetic properties are impaired.

N is added in the range of 0.1 to 20.0 at%, preferably in the range of 1 to 15 at%. N refines crystal grains, lowers coercive force, increases magnetic permeability, and promotes soft magnetization. If N is less than 0.1 at%, fine crystals will not be formed, and good soft magnetic properties cannot be obtained. Also 2
If it exceeds 0 at%, the saturation magnetic flux density decreases to 15 kG or less.

O is added in an amount of 0.1 to 10.0 at%. As described above, the addition of O forms an oxide with R and suppresses the growth of crystal grains. However, the oxide phase is so fine that it may be difficult to detect it by ordinary X-ray diffraction. O
If the content is less than 0.1 at%, good soft magnetic properties cannot be obtained because of insufficient generation of oxide. If it exceeds 10 at%, the saturation magnetic flux density decreases to 15 kG or less. In the present invention, a part of Fe may be substituted with Cr or the like for the purpose of improving corrosion resistance.

When the soft magnetic thin film of the present invention is applied to a thin-film magnetic head, if the saturation magnetic flux density Bs is less than 15 kG, the overwrite characteristics are deteriorated with respect to a high coercive force, especially a magnetic recording medium having a magnetic field of 1400 Oe or more.

N or O is 30 at% of their total amount
The addition amount is particularly preferably 20 at% or less. In some cases, carbon C may be contained by substituting a part of N or O.

The thickness of the soft magnetic thin film can be appropriately selected according to the application, but is usually 0.5 to 6 μm.

Such a soft magnetic thin film of the present invention is usually made of F
It contains a main magnetic layer mainly containing e-Co and a phase mainly containing nitride and / or oxide of R. In particular, the average crystal grain size D of the main magnetic layer is 1000 ° or less, preferably 5 ° or less.
00 ° or less, more preferably 20 to 250 °. Excellent soft magnetic characteristics can be obtained by reducing the particle size in this manner.

The soft magnetic thin film of the present invention can be manufactured by a vacuum film forming method such as ion plating, vapor deposition, CVD, and sputtering. In addition, stress is applied to the soft magnetic thin film because the substrate is used during film formation. Therefore, 200-3
A film is formed at a substrate temperature of 00 ° C.
It is desirable to relax the stress by performing a heat treatment at a temperature of ° C.

The soft magnetic thin film is formed by, for example, the following method. First, an alloy casting or sintered body, or a composite target or the like is used as the target. In order to introduce nitrogen and oxygen into the film, reactive sputtering in an atmosphere of nitrogen and oxygen may be performed, or these elements may be introduced into a target. The sputtering is performed in an inert gas atmosphere such as Ar. In the case of reactive sputtering, 0.1-20% by volume of nitrogen and 0.1% of oxygen are used.
What is necessary is just to contain-2.5 volume%. Alternatively, the surface of the film during film formation may be irradiated with nitrogen ions and oxygen ions using a dual ion beam sputtering (DIBS) device to introduce nitrogen and oxygen into the film.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Thin film samples were produced using a dual ion beam sputtering apparatus having two 100 mm diameter bucket type ion guns. As a substrate, a crystallized glass substrate (a photocell substrate manufactured by Corning Incorporated) was used for evaluation of magnetic properties, and an Al substrate having a purity of 99.85% was used for composition analysis. During the film formation, the substrate was heated at 200 ° C. for stress relaxation. The target used was a composite target in which various rare earth metal element chips were arranged on a ring on an Fe—Co alloy target. Then, Ar ion is emitted by the main ion gun.
The target was sputtered by accelerating the ions to form a film on the substrate. At the same time, an Ar + nitrogen + oxygen mixed gas was ionized by an assist gun, accelerated, and irradiated to the sample, thereby introducing nitrogen and oxygen into the sample. The main film forming conditions are shown below.

Ultimate pressure: 1 × 10 ⁻⁷ Torr Accelerating voltage (main beam): 1200 V Accelerating current (main beam): 135 mA Accelerating voltage (assist beam): 250 V Accelerating current (assist beam): 10 mA Film forming pressure: 1 0.5-2.8 × 1
0 ^-4 Torr Film forming rate: 1Å / sec The thin film sample was subjected to a heat treatment at a temperature of 300 ° C. and a holding time of 1 hour in a vacuum of 1 × 10 ^-5 Torr for stress relaxation.

The obtained thin film sample was evaluated by the following method. 1. Film composition The film composition was determined by an electron probe microanalyzer (EPMA) and an oxygen and nitrogen simultaneous analyzer using a high-frequency combustion method. 2. Saturation magnetic flux density Bs Measured in a magnetic field of 10 kOe using a sample vibration magnetometer (VSM). 3. Saturated magnetostriction λs A thin film sample was placed in a magnetic field of 100 Oe rotating in the plane of the film, and using a laser beam, extension and contraction due to magnetostriction of the sample were detected by a synchronous rectification method to detect λs. 4. The grain size was determined from the half width of the (110) peak of the body-centered cubic crystal by X-ray diffraction using a CuKα1 line. 5. Coercive force Hc Determined using a thin-film hysteroscope. 6. The real component μ ′ and the imaginary component μ ″ were measured in a high-frequency magnetic field of 3 mOe and 5 MHz using a figure-eight coil of the effective magnetic permeability | μ |, and | μ | was determined. The obtained results are shown in Table 1. .

[0022]

[Table 1]

The following can be seen from the results in Table 1. The saturation magnetic flux density Bs is determined by the total amount of Fe and Co, and is 17.5.
２３23.5 kG can be realized. As mentioned earlier, C
By adding o, a higher saturation magnetic flux density can be realized than in the case of using Fe alone. In particular, Co15 to 50at used in Examples
% Is preferred. When Co is added in an amount of 40 at% or more, the saturation magnetic flux density can be as large as 19 to 23 kG. In this case, a magnetic permeability of about 1,000 was obtained. Further, in the sample in which Co is 15 to 20 at%, the saturation magnetic flux density shows a slightly low value of 18.5 to 22.5 kG.
However, in this composition system, the magnetostriction can be made negative by adding a small amount of rare earth element of about 0.5%. Further, by adding nitrogen and oxygen, it is possible to obtain good soft magnetic properties with a magnetic permeability of 2000 or more. Saturation magnetostriction λs
It can be seen that although the Fe type is on the order of 10 ^-6 and the Fe-Co type is on the order of 10 ^-6 to 10 ^-5 , the magnetostriction can be suppressed to some extent even by the addition of the rare earth metal element R (see Samples 1 and 5). Compare sample 9). By adding N and / or O, the magnetostriction can be reduced to a considerable extent (Samples 1 and 2 to 4, Samples 5 and 6 to 8, Samples 9 and 1).
0 each). The crystal grain size D is reduced to some extent by the addition of rare earth metal elements (compare samples 1, 5 and sample 9), but the effect of nitrogen and oxygen is large (samples 1 and 2 to 4, sample 5 and 6). -8, samples 9 and 10 respectively). As the saturation magnetostriction λs and the crystal grain size D become smaller, the coercive force Hc becomes smaller, and the embodiment of the present invention can realize 2.0 Oe or less. The soft magnetic thin film of the present invention also had good heat resistance and corrosion resistance.

[0024]

As described above, according to the present invention, Fe-C
An object of the present invention is to reduce the coercive force Hc, improve the magnetic permeability μ, and improve the corrosion resistance while maintaining a high saturation magnetic flux density in a soft magnetic thin film made of an o-based alloy.

──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-3-160709 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 10/16 G11B 5/31 H01F 41 / 18

Claims (2)

(57) [Claims] 1. The formula Fe _100- α _- β _- γ _- δCoαRβNγOδ (where R is a rare earth element containing Y, 15.0 ≦ α ≦ 55.0 at% 0.1 ≦ β ≦ 5.0 at%) A soft magnetic thin film having a composition represented by the following formula: 0.1 ≦ γ ≦ 20.0 at% (0.1 ≦ δ ≦ 10.0 at%). 2. A soft magnetic multilayer film obtained by laminating the soft magnetic thin film according to claim 1 with a magnetic film having a non-magnetic or other composition.