JP2853923B2 - Soft magnetic alloy 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 alloy film having a high saturation magnetic flux density suitable for a magnetic head for high density recording and the like.

2. Description of the Related Art In recent years, in the field of magnetic recording, higher density has been strongly demanded. Accordingly, the recording wavelength on the recording medium is shortened, and a medium having a higher coercive force (Hc) has been used in order to stably maintain the recording pattern against a demagnetizing field caused thereby. To record on such a medium, a magnetic head that generates a strong magnetic field from the gap is required, and a core material having a high saturation magnetic flux density is required. On the other hand, in the case of a recording / reproducing magnetic head, the core must also have a high initial magnetic permeability (μ) in order to efficiently detect a minute magnetic field from the medium. In order to increase the recording efficiency of the magnetic head, it is effective to make the magnetic field distribution in the gap portion steep. As a suitable magnetic head, a thin film head and a high saturation magnetic flux density thin film are arranged only in the vicinity of the gap. Metal-in-gap (MIG) type heads are mentioned. In addition to the above-described improvement in the linear recording density, the improvement in the track density is also important for the improvement in the areal recording density, and the track narrowing of the head is being promoted. In order to process the head into a narrow track, a thin film head processed by photolithography is advantageous. Further, the thin film head has a shape that is advantageous for high frequency operation. As described above, it is strongly demanded that the core material of the magnetic head has a high saturation magnetic flux density and good soft magnetic properties in the form of a thin film.

[0002]

Various thin films having Fe as a main component have been proposed as high saturation magnetic flux density thin films. For example, the present inventors have obtained an example of obtaining excellent soft magnetic properties by remarkably reducing the crystal grains containing Fe as a main component (effective reduction of crystal magnetic anisotropy).
278220 and Japanese Patent Application No. 1-298829. The upper limit of the saturation magnetic flux density was about 18 kG. Even if pure iron is softened by any method, its saturation magnetic flux density is 21.5 kG. In the future, in order to further increase the recording density, it is expected that a higher saturation magnetic flux density will be required. Co (1
(0-70 at%) has a higher saturation magnetic flux density than Fe.
at%) alloys are known to have a saturation magnetic flux density as high as 24.5 kG (room temperature). An Fe—Co (Co; 50 at%) alloy having a saturation magnetic flux density of 24.0 kG is called “permendur” and has already been put to practical use as a bulk material. However, when this alloy is manufactured as a thin film, it is extremely difficult to obtain good soft magnetic properties. This is because the Fe—Co alloy is + 8 × 10 ^−5.
This is due to having a large magnetostriction. That is, a thin film produced by a thin film forming process such as sputtering or vapor deposition has an internal stress of 10 ⁸ to 10 ¹⁰ dyn / cm ² , and it is practically impossible to reduce this to zero. Due to the inverse magnetostriction effect caused by this stress, a large magnetic anisotropy occurs in each crystal constituting the thin film. In a polycrystalline thin film, such anisotropic dispersion (heterogeneity) becomes remarkable, so that smooth magnetization reversal is not performed and soft magnetic characteristics cannot be obtained. Since such anisotropy is extremely large, it is difficult to obtain soft magnetic characteristics that can be put to practical use, even if the crystal is refined and reduced. In order to solve this, it is necessary to reduce the magnetostriction of the Fe—Co alloy crystal. As a method therefor, it has already been proposed to add a large amount of Si or Al. (Papers N. Tsuya, K. Arai, K. Ohmori, and T. Honma: IEE
E Trans.Magn, MAG-18 (1982) 1424., M. Hayakawa, KH
ayasi, W. Ishiwata, Y. Ochiai, M. Matsuda, Y. Iwasaki a
nd K. Aso: IEEE Trans. Magn. MAG-23 (1987) 3092.) However, the addition of a large amount of these non-magnetic elements causes the saturation magnetic flux density to be less than 20 kG, so there is not much advantage over Fe-based thin films. Was.

[0003] The present invention solves the above-mentioned problems and provides Fe-
The object is to reduce the essential magnetostriction of the Fe—Co alloy crystal while maintaining the high saturation magnetic flux density of the Co alloy, and to obtain a thin film having soft magnetism.

[0004]

According to a first aspect of the present invention, there is provided a soft magnetic alloy film having a composition of Fe x Co y Sm z (Fe: iron, Co: cobalt, Sm: samarium). It is characterized by being made of a cubic crystal. However, 30 at% ≦ x ≦ 95 at% (at% = atomic percent) 5 at% ≦ y ≦ 70 at% 0.2 at% ≦ z ≦ 5 at%

According to a second aspect of the present invention, there is provided the high saturation magnetization soft magnetic alloy film according to the first aspect, wherein the average grain size of the crystal grains is 40 nm or less.

In an equilibrium state, Sm hardly forms a solid solution with Fe or Co, but can be forcibly made into a solid solution (form a non-equilibrium phase) by a so-called gas phase quenching process such as sputtering or vapor deposition. is there. When a compound having a different crystal structure is precipitated, properties such as saturation magnetization change greatly. In this case, Fe-Co having a high saturation magnetization is used.
A small amount of Sm can be solid-dissolved while maintaining the body-centered cubic lattice (bcc) structure. Vacuum evaporation or RF bipolar sputtering, magnetron sputtering, 3
Existing thin film manufacturing apparatuses such as polar sputtering, ion beam sputtering, and facing target type sputtering can be used.

[0007]

The essential cause of magnetostriction is the interaction between electron spins. That is, if the crystal structure does not change,
When elements having different electronic states form a solid solution, the interaction between spins changes and magnetostriction changes. Rare earth metals can be considered as elements that can be expected to have a large effect as described above. Unlike the 3d transition metal, the rare earth metal has an orbital magnetic moment that is alive (3d transition metal has only a spin magnetic moment). Interaction. There is a one-ion model as a model for explaining magnetic anisotropy from the behavior of orbits of magnetic ions in such a crystal field, but a change in magnetostriction can be expected by a similar mechanism. From such a viewpoint, the present inventors have conducted intensive studies and, as a result, have found that among rare earth elements, Sm has an effect of reducing the magnetostriction of Fe—Co. Here, unless the Sm concentration (z) is 0.2 at% or more, the effect cannot be clearly seen. If Sm is added in an amount of 5 at% or more, the single phase state of the body-centered cubic structure cannot be maintained, and an amorphous phase is mixed, thereby lowering the saturation magnetic flux density. Note that in FeχCoySmz, 30 ≦ χ ≦ 9
The reason for setting 5 at% and 5 ≦ y ≦ 70 at% is to obtain a higher saturation magnetic flux density than Fe. By the way, as described above, Sm is insoluble in Fe and Co in an equilibrium state. It is known that when such a non-solid solution material is forcibly dissolved, crystal grains are refined. Such miniaturization, combined with the above-described effect of reducing magnetostriction, further reduces the effective anisotropy, so that better soft magnetic characteristics can be obtained. When the crystal grain size is larger than 40 nm, such an effective anisotropy reduction effect does not appear. In order to further promote such crystal refinement, it is effective to irradiate the substrate with ions during film formation.

[0008]

EXAMPLE An Fe-Co-Sm alloy film was formed on a water-cooled copper substrate using a DC triode high-speed sputtering apparatus. The alloy target was produced by arc melting. A during sputtering
r gas pressure is 4 × 10 ^-2 Torr. Target voltage 1kV
And The measurement of magnetostriction was performed in a state where the magnetostriction was separated from the substrate by a strain gauge. The saturation magnetic flux density was measured with a sample vibration magnetometer. The crystal structure was identified by X-ray diffraction. As an example, with the Sm concentration kept constant at 0.5 at%, Fe:
FIG. 1 shows the change in magnetostriction when the ratio of Co was changed. As a comparative example, bulk Fe—Co containing no Sm
The alloy is indicated by a dashed line. As is clear from FIG. 1, the addition of only 0.5 at% of Sm causes the magnetostriction to change in the negative direction. In the soft magnetic alloy film of this embodiment, Fe: Co ≒ 8
It is understood that the magnetostriction can be reduced to about 10 ^{−6 at} around 5:15. FIG. 2 shows a change in the saturation magnetic flux density of the alloy film having an Sm of 0.5 at% depending on the Fe: Co ratio. These have a crystal structure of body-centered cubic structure, and F
Even when compared with a bulk alloy of e-Co (Comparative Example; broken line), the decrease in the saturation magnetic flux density is not large. Further, Fe: Co =
It can be seen that the alloy film of this example having a Co concentration of about 93: 7 has a higher saturation magnetic flux density than pure iron. As can be seen from FIGS. 1 and 2, among the alloy films of this example, Sm contained 0.5 at% and Fe: Co = 85: 15.
The alloy film in the vicinity has a small magnetostriction of the order of 10 ^-6 and 22.
It has a high saturation magnetic flux density of about 1 kG.

Table 1 shows the measured values of the magnetostriction and the saturation magnetic flux density for each Sm concentration in the soft magnetic alloy film.

[0010]

[Table 1]

From Table 1, it can be seen that the magnetostriction can be reduced by increasing the Sm concentration to some extent.
However, when the Sm concentration exceeds 5 at%, the saturation magnetic flux density is significantly reduced. This is presumably because when the Sm concentration increases, an amorphous phase having a low Curie temperature is mixed.

[0012]

The soft magnetic alloy film of the present invention has a body-centered cubic structure by adding a small amount of Sm, and has a reduced magnetostriction while maintaining a high saturation magnetic flux density. Pure iron (Bs
= 21.5 kG), it is possible to soften the thin film having a higher saturation magnetic flux density. When such a thin film having a very high saturation magnetic flux density is applied to a magnetic head, it becomes possible to generate a strong magnetic field from a minute track and a minute gap. A head can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between magnetostriction and Co ratio in an alloy.

FIG. 2 is a graph showing the relationship between the Co ratio in the alloy and the saturation magnetic flux density.

Continuation of the front page (72) Inventor Naoya Hasegawa 1-7 Yukiya Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (56) References JP-A-1-290733 (JP, A) JP-A-57-51237 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00-38/60 C22C 19/07 G11B 5/31 H01F 10/14

Claims (2)

(57) [Claims] 1. Fex Coy Sm z (Fe: iron, C
o: cobalt, Sm: samarium), and a high saturation magnetization soft magnetic alloy film characterized by being entirely composed of a crystal having a body-centered cubic structure. However, 30 at% ≦ x ≦ 95 at% (at% = atomic percent) 5 at% ≦ y ≦ 70 at% 0.2 at% ≦ z ≦ 5 at% 2. The high saturation magnetization soft magnetic alloy film according to claim 1, wherein the average grain size of the crystal grains is 40 nm or less.