JPH07114164B2 - Magnetic artificial lattice film - Google Patents

Description

The present invention relates to a magnetic artificial lattice film suitable for a magnetic pole of a thin film head for magnetic recording and the like.

[Problems to be solved by the prior art / invention]

For example, when trying to increase the magnetic recording density of a magnetic file device, a magnetic material having a large coercive force (Hc) is used for the recording medium, and at the same time, the magnetic head has a high saturation magnetic flux density (Bs) that can sufficiently magnetize the recording medium. ) Is required, and in order to efficiently focus the leakage magnetic flux from the recording medium, the one made of a good soft magnetic material is required. As a head satisfying such a condition,
Ring heads obtained by machining ferrites have been used. However, since the high saturation magnetic flux density and the fine processing are approaching their limits, a thin film magnetic head obtained by the fine processing technology applying the photolithography technology and the magnetic thin film is currently used. NiFe alloys (Bs-1 Tesla) by vacuum deposition, sputtering, and plating have been used for magnetic thin films for thin-film magnetic heads, but it is difficult to write on high coercive force media of 1000 Oersteds or more. is there. By the way, although researches on new materials have been actively conducted in recent years, in particular, an artificial lattice film has an extremely small thickness, and by periodically laminating these films, the properties of the main body of the layers constituting them are improved. Since it exhibits different properties from, it has attracted attention in terms of physical properties as a substance showing new properties completely different from bulk properties, both in terms of physical properties and in applications.

An Fe film is promising as a high Bs ferromagnetic metal film, but it cannot be used as a magnetic pole for a head as it is because of its strong crystal magnetic anisotropy and large coercive force. Further, it has a drawback that it is easily oxidized in the air, which is an obstacle to practical use. Conventionally, as a method of improving the soft magnetic characteristics of a ferromagnetic Fe metal film, C and Si are mixed as an Fe base. (For example, "Feromaznetism" by Bozolf, DV Norstrand Co.) However, according to this method, C and Si are non-magnetic, so that there is a drawback that Bs is lowered. Also, by forming a Fe film in a nitrogen atmosphere by the Spat method, good soft magnetic properties are obtained (for example, J.Appl.Phys. 61 P3841 (1987)), but this film lacks thermal stability. There is a problem.

Therefore, there has been a strong demand to provide a ferromagnetic film that retains high Bs, which is a characteristic of a ferromagnetic Fe metal film, is hard to oxidize, and has good soft magnetic characteristics with a small coercive force.

An object of the present invention is to provide a magnetic artificial lattice film having a high Bs, being thermally stable, being hard to oxidize, having good soft magnetic characteristics, and having a controlled magnetostriction constant.

[Means for solving problems]

The present invention is a conventional Ni-Fe alloy or high Bs
Unlike alloy films such as Fe-Si and Fe-C, which are promising as materials, the main feature is that they are magnetic artificial lattice films in which Ni layers and Fe layers are alternately laminated. The Ni and Fe layers are materials that have been widely used, but by forming an artificial lattice film with the Ni layer and the Fe layer, for example, the crystallinity of the Fe layer collapses and changes to good soft magnetic characteristics, or magnetic parts A new phenomenon that has never existed before is utilized, such as the effect of magnetostriction that changes the magnetic domain structure, which is a problem during processing and reproduction of the magnetization signal, can be controlled by the thickness of the Ni or Fe layer and the lattice period.

The present invention has a repeating periodic structure in which Ni layers and Fe layers are alternately laminated, and the lamination cycle is 50 nm or less. The reason is that if the period exceeds 50 nm, the coercive force becomes 4 Oersted or more and it becomes difficult to use as a magnetic pole for a magnetic head.

In addition, the thickness of each metal layer, the thickness of the Ni layer is 4nm or less, F
The thickness of the e layer is 46 nm or less. The reason is that if the thickness of the Ni layer exceeds 4 nm, the magnetostriction constant becomes a large negative value, and a good magnetic repetitive structure cannot be obtained, making it difficult to use as a magnetic pole for a magnetic head.

〔Example〕

 An embodiment of the present invention will be described below.

FIG. 2 shows an example of an apparatus for producing an artificial lattice film according to the present invention. Reference numerals 1 and 2 are Ni and Fe targets, respectively, and 3 is a substrate on which an artificial lattice film is deposited. Reference numeral 4 is an ion source for sputtering the target, and 5 is a holder for supporting the target. Since the operating vacuum degree during artificial lattice deposition is 1 × 10 ⁻⁴ Torr and the substrate temperature does not rise more than necessary during film deposition, the apparatus using the ion beam sputtering structure is a multilayer film and an artificial lattice film. Is advantageous for producing.

In the above structure, the target shown by the rare gas ion 1 such as argon generated by the ion source is irradiated, and the Ni layer is deposited on the substrate 3 by sputtering. After that, the target holder 5 is rotated, the target 2 is irradiated with ions, and the Fe layer is superposed and deposited on the substrate. This procedure is repeated to form the artificial lattice. The lattice period and the film thickness of the Ni and Fe layers are controlled by the sputtering time and the current density of ions.

FIG. 1 is a diagram showing the structure of the artificial lattice film produced as described above.

As shown in the figure, the artificial lattice film has a Ni layer 6 and a Ni layer 6 on the substrate 3.
The Fe layer 7 and the Fe layers 7 are alternately laminated to form a repeating periodic structure. Here, for the sake of later description, the thickness of each of the Ni layer and the Fe layer is defined as t Ni, t Fe, and one artificial lattice period consisting of each of these layers is defined as tp (= t Ni + t Fe).

FIG. 3 shows the change of the saturation magnetic flux density (Bs) in the Ni / Fe artificial lattice film according to the present invention with respect to the thickness of the Ni layer and the Fe layer.
As shown in the figure, by changing the thickness of the Ni and Fe layers, B
It is possible to change s from 2.25T for pure Fe to 0.55T for pure Ni.

Fig. 4 shows the relationship between Bs, coercive force (Hc) and lattice period tp when the film thickness ratio of Ni and Fe layers is 1. The total number of lattices is set so that the total film thickness is 600 nm, and the temperature of the substrate is set to 160 degrees. Since the Ni layer thickness ratio is 50%, Bs is almost 1.
It is constant at 35T. When the period was 50 nm or less, Hc changed to 40e or less, and the good soft magnetic characteristics were obtained. Such a change in magnetic characteristics is interpreted as follows. The thin Fe layer grown on the Ni layer having the FCC structure cannot have the original BCC structure due to the misfit of the crystal lattice, and becomes the Ni / Fe artificial lattice film in the state where the crystallinity is deteriorated. (The above items were confirmed by X-ray diffraction and electron beam diffraction.) Therefore, the crystalline anisotropy of the Fe layer collapses, and the induced anisotropy due to the magnetic field is Ni, F.
It is considered that the soft magnetic properties were induced by the e and Ni / Fe layer interfaces and changed. Therefore, when the period is increased, the properties of the Fe layer come closer to the properties of the original bulk.
Is considered to have increased and deteriorated.

FIG. 5 shows the relationship between the magnetostriction constant (λs) and the lattice period. The sample is the same as in FIG. The magnetostriction constant becomes 0 at a period of 4.7 nm, and the influence of magnetostriction on the magnetic domain structure at the time of processing the head or reproducing the magnetization signal can be reduced. In the Ni-Fe alloy, a magnetostriction constant of 0 can be realized with a composition of 80 wt% Ni and 20 wt% Fe, and Bs at this time is almost 1T. In the Ni / Fe artificial lattice as an example of the present invention, a magnetostriction of 0 can be realized at 1.35T.

FIG. 6 shows the relationship between Bs, Hc and the Fe layer film thickness (t Fe). The thickness of the Ni layer was 2 and 4 nm. The total film thickness and the substrate temperature were set to 600 nm and 160 degrees. By increasing the thickness of the Fe layer, Bs increases, and by setting the thicknesses of the Ni and Fe layers to 2 and 10 nm, respectively, Bs to 1.96T can be realized. Also, the Fe layer is 4
By setting the thickness to nm or more, good soft magnetic characteristics with Hc of 10 Oe or less are obtained regardless of the Ni layer thickness.

FIG. 7 shows the relationship between λs and the Fe layer thickness. When the Ni film thickness is 2 nm, the magnetostriction constant of 0 can be realized at the Fe film thicknesses of 1.5 and 10 nm.
Thus, by setting the Ni layer and the Fe layer to 2 nm and 10 nm, respectively, Hc is 10e or less and Bs is 1.96T, and at the same time, the magnetostriction constant 0 can be realized.

FIG. 8 shows changes in Bs and Hc when the thickness of the Ni layer was changed while the Fe layer was kept constant at 10 nm. By setting the thickness of the Ni layer to 2 nm or more, good soft magnetic characteristics change, but Bs is
It decreases as the Ni layer becomes thicker.

FIG. 9 shows the relationship between the magnetostriction constant and the Ni layer. Ni
A magnetostriction constant of 0 can be realized at a layer thickness of 2 nm, but as the Ni layer is made thicker, it changes to a large negative magnetostriction. As mentioned above,
The thickening of the Ni layer is not effective in terms of lowering Bs and achieving λs˜0.

FIG. 10 shows magnetic domain structures of Ni / Fe artificial lattice films having various magnetostriction constants. The changes in the magnetostriction constants of these magnetic domain structures are similar to those found in NiFe alloys, etc., and a good magnetic domain structure is shown in Fig. 10 (b), which has a small magnetostriction constant, and is applied to magnetic parts such as thin film heads. Means to do.
Furthermore, when the influence of the substrate temperature on the magnetic properties of the Ni / Fe artificial lattice with a period of 10 nm was investigated, some period disturbance appeared at 300 degrees or more, but Bs and Hc were hardly affected. . From this fact, the Ni / Fe artificial lattice film according to the present invention is also thermally stable.

In addition, by adding a non-magnetic insulating film such as SiO ₂ to the Ni / Fe artificial lattice film of the present invention, it is possible to improve the magnetic domain control of the magnetic film and the frequency characteristics of magnetic permeability. An embodiment in this case is shown in FIG. 6 is a Ni layer, 7 is a Fe layer, and 8 is a non-magnetic insulating layer.

As is clear from the above results, the Ni / Fe artificial lattice film according to the present invention can control a high Bs of 1.35 to 1.96 T, and by setting the period of the artificial lattice to 50 nm or less, the coercive force of a good soft magnetic field is small. The characteristics can be realized. Further, by setting the Ni and Fe layers to 2 and 10 nm, respectively, a magnetostriction constant of 0 can be realized at Bs to 1.96T, and it is possible to reduce the effect of magnetostriction on the magnetic domain structure peculiar to the magnetic component. In addition, the temperature
Excellent soft magnetic properties are maintained and thermal stability is excellent even at temperatures above 300 degrees. Regarding the oxidation resistance, the Ni layer, which is more difficult to oxidize than the Fe layer, has a structure sandwiched between them, so that the Ni / Fe artificial lattice film is hard to oxidize.

〔The invention's effect〕

As described above, since the Ni / Fe artificial lattice film according to the present invention has high Bs and good soft magnetic characteristics, when used for a magnetic pole such as a thin film head, the magnetization signal of a high coercive force medium is efficiently recorded. It has the advantage of being reproducible. Also Fe
It is possible to control the magnetostriction constant by changing the layer thickness, and it is possible to reduce the effect of magnetostriction on the magnetic domain structure, which is a problem during processing of magnetic parts or reproduction of the magnetization signal. Can manufacture magnetic parts. Furthermore, since the Ni layer is added to the Fe layer as a base, the problems of oxidative corrosion and thermal instability that tend to occur in the Fe film can be solved, and there is an advantage that a highly reliable magnetic component such as a thin film head can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an apparatus for producing an artificial lattice film according to the present invention, and FIG. 3 is a diagram showing dependency of Bs on lattice film thickness. , Fig. 4 is B
Fig. 5 is a diagram showing the lattice period dependence of s, Hc, Fig. 5 is a diagram showing the period dependence of λs, Fig. 6 is a diagram showing the dependence of Bs, Hc on the Fe layer film thickness, and Fig. 7 is a diagram showing the dependence of λs on Fe. FIG. 8 shows the dependency of layer thickness,
Fig. 9 is a diagram showing the dependence of Bs and Hc on the Ni layer thickness, Fig. 9 is a diagram showing the dependence of λs on the Ni layer thickness, and Figs. 10 (a) to (c) are Ni / Fe artificial materials having various magnetostriction constants. Fig. 11 shows the magnetic domain structure of the lattice film.
The drawing is a cross-sectional view showing another embodiment of the present invention. 3 ... Substrate, 6 ... Ni layer, 7 ... Fe layer.

Claims (4)

[Claims] 1. A substrate has a repeating periodic structure in which Fe layers and Ni layers are alternately laminated, and the lamination period is 50.
the thickness of the Ni layer is 4 nm or less and the thickness of the Fe layer is 46 n or less.
A magnetic artificial lattice film having a thickness of m or less. 2. When the thickness ratio of the Fe layer and the Ni layer is 1, the period is
The magnetic artificial lattice film according to claim 1, which has a thickness of 4.0 nm to 5.4 nm. 3. The magnetic artificial lattice film according to claim 1, wherein when the Ni layer has a thickness of 2 nm, the Fe layer has a thickness of 1 to 2 nm or 9 to 11 nm. . 4. The thickness of the Ni layer is 10 nm when the thickness of the Fe layer is 10 nm.
Claim 1 characterized in that it is 1.5 to 2.5 nm.
The magnetic artificial lattice film according to the item.