JPH0352641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a magnetic head for perpendicular magnetic recording.

2. Prior Art Conventionally, magnetic recording media such as magnetic tapes and magnetic disks have been widely used for recording various electrical signals such as video, audio, and digital signals. In a method that uses magnetization in the in-plane longitudinal direction of a magnetic layer (magnetic recording layer) formed on a substrate, higher density is being achieved by using new magnetic materials and new coating techniques. On the other hand, in recent years, with the increase in the density of magnetic recording, a perpendicular magnetization recording method that uses magnetization in the thickness direction of the magnetic layer of a magnetic recording medium (so-called perpendicular magnetization) has recently been proposed (for example, ,
"Nikkei Electronics" August 7, 1978 No.
192). According to this recording method, as the recording wavelength becomes shorter, the demagnetizing field that acts on the residual magnetization in the medium decreases, so it has favorable characteristics for increasing density, and is essentially suitable for high-density recording. It is a suitable method and research is currently being conducted to put it into practical use.

3. Object of the Invention The object of the present invention is to provide a magnetic head for perpendicular magnetic recording, which is suitable for the above-mentioned magnetic recording system and can be expected to have high magnetization, low coercive force, and high corrosion resistance.

4. Structure of the Invention That is, the present invention provides an auxiliary magnetic pole disposed on one surface of a magnetic recording medium, and a main magnetic pole for perpendicular magnetic recording disposed on the other surface of the magnetic recording medium. It consists of a base body arranged almost perpendicular to the magnetic recording surface of the magnetic recording medium and a magnetically permeable layer provided on this base body, and at least a part of this magnetically permeable layer has a higher saturation magnetization than pure iron. α−Fe
This invention relates to a magnetic head for perpendicular magnetic recording, which is formed by a facing target sputtering method using a mixed phase of γ'-Fe ₄ N and γ'-Fe ₄ N single phase.

5 Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a magnetic head 16, which is used for perpendicular magnetic recording on a magnetic recording medium 15 such as a magnetic tape.
17. Of these, the head 16 functions as an auxiliary magnetic pole, and the head 17 placed opposite thereto functions as a main magnetic pole.

What is characteristic here is that the main magnetic pole 17 is made of iron nitride (FexN), especially γ'-Fe ₄ N, on the glass substrate S.
Or a magnetic film 14 made of (α-Fe+γ′-Fe ₄ N)
and attach it to a holder 1 such as another glass plate.
The reason is that a structure protected by 8 is used. As will be clear from what will be described later, FexN constituting the magnetic film 14 has a large saturation magnetization and is capable of sufficient signal recording, while at the same time exhibiting a low coercive force (Hc) required for the head. Therefore, the performance of the head having such a magnetic film 14 as a magnetically permeable layer is extremely good. Furthermore, FexN also has good corrosion resistance due to the nitrogen content, which also contributes to improved head characteristics.

Note that, for example, in this perpendicular magnetic recording method, the auxiliary magnetic pole 16 is excited by a magnetic signal, and a magnetic field is generated from there toward the medium 15 side, which causes flux to concentrate in the in-plane direction toward the main magnetic pole 17. Magnetic recording corresponding to the main pole 17 is performed on the magnetic layer of the medium 15 .

FIG. 2 shows a magnetic head 27 as a reference example of the present invention, and in this head as well, magnetic films 14 made of FexN are formed on the opposing surface of the core material S made of ferrite, for example, on the magnetic gap 20 side. has been done. Note that the entire head may be covered with FexN. These heads made of FexN are particularly suitable for high-density recording.

Furthermore, the FexN magnetic film 14 described above can also be formed on magnetic heads other than those described above (for example, thin film heads).

Next, a method of manufacturing the above magnetic head will be explained.

First, the substrate S (glass plate, ferrite core material, etc.)
is prepared, and a FexN film 14 is formed on a predetermined surface thereof by the method described below. For this,
It is desirable to use the ion beam generator shown in FIGS. 3-8.

The apparatus shown in FIG. 3 basically consists of a facing target sputter section A and an ion beam extraction section B that extracts ionized particles from this sputter section.

In the sputter section A, 1 is a vacuum chamber, and 2 is a gas introduction pipe for introducing a predetermined gas (Ar+N ₂ ) into the vacuum chamber 1 and setting the gas pressure to about 10 ^-3 to ^{10 -5} Torr. The exhaust system of the vacuum chamber 1 is not shown.

The target electrodes are configured as opposed target electrodes in which a pair of targets T ₁ and T ₂ made of Fe are separated from each other by a target holder 4 and are placed facing each other in parallel. A magnetic field is formed between these targets by external magnetic field generating means (magnetic coil) 3. In the figure, 5 is a cooling water inlet pipe, 6 is a cooling water outlet pipe, and 13 is an acceleration electrode.

In the sputtering device configured in this way,
A magnetic field is formed in a direction perpendicular to the surfaces of both targets T ₁ and T ₂ facing each other in parallel, and this magnetic field creates a gap between the cathode fall area (i.e., between targets T ₁ and T ₂ as clearly shown in FIG. 4). The γ electrons emitted by the impact of the sputtering gas ions accelerated by the electric field on the target surface in the regions 8, 9) between the generated plasma atmosphere 7 and each target _T1 and _T2 are transferred to the space between the targets. Lock it in and move it towards the other target. The γ electrons that have moved to the other target surface are reflected by the cathode fall section nearby. Thus, the γ electrons reach the target T ₁ −T ₂
In between, the reciprocating motion is repeated while being constrained by a magnetic field. During this reciprocating motion, the γ electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the release of γ electrons from the target and the ionization of the atmospheric gas. . Therefore, a high-density plasma is formed in the space between the targets _T1 and _T2 , and the target material is sputtered sufficiently.

Compared to other flying methods, this facing target sputtering device enables film formation at a high deposition rate using high-speed sputtering, and the substrate is not directly exposed to plasma, allowing film formation at low substrate temperatures. is possible.

The structure of the device shown in Fig. 3 that should be noted is that the Fe ejected from the target in the spatter section A
The present invention has a derivation section B for efficiently deriving ionized particles, ie, FexN ions, to the outside through the reaction between the reactant gas (N 2 ) and the reaction gas (N ₂ ). That is, this derivation part B has a screen grid G arranged near the outside of the target T ₂ , and the target T ₂ and the grid G are each held at a predetermined potential, and at the same time, the ionized particles 10 are Small holes 11 and 12 for passage are formed in corresponding numbers and patterns, respectively. This is clearly shown in FIGS. 5 and 6, respectively. Each small hole 11, 12 may have a diameter of 2 mm, for example, and be formed with an interval of 5 mm, and the thickness of the grid G may be 1 mm.

FIG. 7 schematically shows an electric circuit system for operating the above device.
With Vp applied, a negative voltage Vt is applied to both targets T ₁ and T ₂ , and grid G is grounded.
Further, the substrate S disposed on the side of the ion beam deriving section B is also grounded. FIG. 8 shows the potential distribution of each part, where Vp is set to 0 to 200V and Vt is set to 500 to 1000V.

When the above device is operated under such conditions, ions in the plasma generated in the sputtering section A (vacuum level 10 ^-3 to ^{10 -4} Torr) are transferred to the lower target T _{2 .}
After being accelerated by the accelerating electrode 13 in the cathode descending section 9 (see Fig. 4), the small hole 1 is decelerated by the electric field between the target T ₂ and the grid G.
1 and 12, and is extracted with energy corresponding to the potential difference between the substrate S and the plasma.
The derived ion beam 10 is effectively focused by the action of the electric field E (see Fig. 3) formed on the side of the deriving section B (vacuum level 10 ^-5 Torr or higher), and the above energy is used to direct the ion beam 10 toward the substrate S. It will be incident on .
In this way, by changing the anode voltage Vp applied to the accelerating electrode (or anode) 13, the ion beam 10 is efficiently extracted by the action of the grid G while controlling the energy of the ions (FexN) deposited on the substrate S. It can be guided onto the substrate S. Furthermore, since the side on which the substrate S is located is drawn to a high vacuum of 10 ^-5 Torr or more, a clean magnetic film with few impurities can be deposited.

Note that it is better not to make the small holes 11 and 12 of the target _T2 arranged on the side from which the ion beam is extracted more than necessary; This is likely to cause unnecessary gas to leak to the side, resulting in a decrease in the purity of the deposited film, or it may be undesirable in terms of the strength of the target _T2 and the grid G, and furthermore, the target area may be reduced, resulting in a decrease in sputtering efficiency. .

By using the method and apparatus described above, it is possible to fabricate a magnetic head having a FexN magnetic film 14 having a thickness of, for example, 2000 Å on a substrate S, as shown in FIGS. 1 and 2, for example. This magnetic head has a magnetic film 14 suitable for in-plane longitudinal recording and perpendicular magnetic recording, particularly for high-density recording.

Next, the above magnetized film (FexN) will be described in more detail based on experimental results.

(A) Structure of FexN film All of the formed films exhibit crystallinity, and the crystal structure depends on the nitrogen gas mixture ratio and substrate temperature (Ts).
and varied depending on the ion acceleration voltage (Vp).

In Figure 9, total pressure Ptotal=5×10 ^-4 Torr, Vp
The relationship between the crystal structure of a film prepared under the condition of =20V (constant) and P _N2 / Ts (however, the substrate is (111)
Si substrate). When Ts = 200℃, the crystal phase formed changes from a mixed phase of α-Fe and γ′-Fe ₄ N → a single phase of γ′-Fe ₄ N → ε → Fe ₃ N and ζ-Fe as P _N2 increases. ₂ N
The mixed phase of ζ → Fe ₂ N changes, and the degree of nitridation of the film increases. In addition, an unknown crystal phase (UK) with a lattice spacing of 1.9 to 2.0 Å was present in the α-Fe and γ′-Fe ₄ N mixed-phase film. When Ts rises above 200°C, the boundaries between each region move toward the high P _N2 side. Even when Ts is below 200℃, there is a tendency for the degree of nitridation of the film to decrease as Ts decreases, and Ts
At =80°C and P _N2 ≦4×10 ^-5 Torr, only the α-Fe phase was formed.

FIG. 10 shows X-ray diffraction patterns of examples of films formed under various conditions. Among the phases formed, the ε phase and ζ phase showed random crystal orientation, but the α-Fe phase with the bcc structure had a <110> direction,
The <100> direction of the γ′-Fe ₄ N phase with the fcc structure was strongly oriented perpendicular to the film surface. Conventionally, α-Fe and γ′-Fe ₄ N films, which are fabricated by the normal sputtering method using only neutral particles as deposited particles, have been produced by (110) and (111) planes (of each phase) as the atmospheric pressure decreases. The above results indicate that in the ion beam deposition method of the present invention, the high kinetic energy and uniform directionality of the deposited particles promote the orientation of the film. This can be said to indicate that the oriented planes are affected by the charge of the deposited particles, and that depending on the type of compound, planes other than the closest-packed planes become more likely to be oriented.

In addition, Ptotal=5×10 ^-4 Torr, P _N2 =1.5×
Changes in the X-ray diffraction pattern of a film prepared under constant conditions of 10 ^-5 Torr and Ts = 150°C due to Vp were investigated. At Vp=0V, α-Fe with (110) plane oriented
Only the phase diffraction line, but at Vp = 40V, γ′−Fe ₄ N
Broad peaks clearly appear at the (111) and (200) plane diffraction positions, and α-Fe again appears at Vp = 60V.
Only the diffraction lines of the phase (110) plane are present. these are,
It is shown that in the range of Vp = 0 to 40V, the ratio of the amount of γ'-Fe ₄ N phase increases as Vp increases. Furthermore, the orientation of the γ'-Fe ₄ N phase in the film deposited at Vp = 40V and Ts = 150°C is random, and the γ' phase in the film deposited at Vp = 20V and Ts = 200°C is ( 200) The orientation was different from that shown.
An increase in Vp results in an increase in the kinetic energy of the deposited ions, which increases the surface temperature of the substrate and the mobility of the deposited particles at the substrate surface.
It is thought that as a result, the reaction between iron and nitrogen was promoted. The result for Vp = 60V indicates that when the kinetic energy of the ions becomes excessive, the bond between iron and nitrogen is suppressed, or even if they are once bonded, they are re-separated due to impact from another particle. it is conceivable that. Furthermore, it can be said that the orientation of the film decreases due to the impact of the high-energy particles generated by the increase in Vp on the substrate.

(B) Saturation magnetization of FexN film The saturation magnetization (4πMs) of the film was measured using a magnetic balance. FIG. 11 and FIG. 12 show the relationship between 4πMs and each manufacturing condition. Ptotal=5×
The dependence of 4πMs on P _N2 and Ts of a film prepared under the conditions of 10 ^-5 Torr and Vp = 20 V (constant) is shown.
In 4πMs, the crystal structure of the film is α−Fe+γ′−Fe ₄ N+
In the UK (Unknown) mixed phase case and in the γ′ single phase region, the value exceeds the 4πMs (21.6KG) of pure iron, and the value is particularly high at approximately 25KG near the boundary between the two regions. . This high 4πMs is
This can be said to be caused by the γ' phase and UK phase. This region of high 4πMs is indicated by diagonal lines in FIG. 9, and in this region, both high 4πMs and low Hc can be obtained, making the FexN film suitable as a head material. The reported 4πMs of the γ′ phase is about 24KG,
The values of the γ' single-phase film in the present invention are also approximately the same at 22 to 24 KG. Therefore, the 4πMs of the membrane is
Reaching 25KG means that the 4πMs of the UK phase is higher than that of the γ′ phase. High 4πMs
Since the film was obtained near the boundary between α+γ′+U.K. and the γ′ single phase region, it is possible that the UK phase is Fe ₈ N.

The production condition range in which a film with high 4πMs can be obtained under Ptotal=5×10 ^-4 Torr and Vp=20V is as follows:
When Ts=250℃ constant, P _N2 =1.1×10 ^-5 ~4.0×
10 ^-5 Torr (nitrogen gas mixture ratio P _N2 /Ptotal=2.0~
8.0%), P _N2 = 3 × 10 ^-5 Torr constant, Ts =
The temperature was 150-250℃. Compared to the condition P _N2 /Ptotal=2.7 to 4.0% under which a high 4πMs can be obtained with a film deposited using a normal R sputtering device, the range of the nitrogen gas mixing ratio is wider. high
It has been reported that the Fe ₈ N phase with 4πMs is vulnerable to substrate impact by high-energy particles and increases in substrate temperature; If the plasma potential or sputtering efficiency changes, resulting in substrate impact effects of high-energy particles or fluctuations in substrate temperature, which act in a direction that inhibits crystal growth (e.g. destruction of metastable phases), the formation range becomes narrower. . On the other hand, in the ion beam deposition method of the present invention, the nitrogen gas mixture ratio can be changed independently, so it is thought that the range of fabrication of high 4πMs films has been expanded.

In addition, when we measured the change in 4πMs due to Ptotal, we found that as Ptotal increases, the
It was found that the substrate temperature at which a film with 4πMs can be obtained tends to increase. This is considered to be because the crystallinity of the formed film decreases due to a decrease in the proportion of ions in the deposited particles as Ptotal increases.

FIG. 13 shows the change in 4πMs due to Vp.
The sample here is Ptotal=5×10 ^-4 Torr, Ts
=150℃ and Ptotal=1×10 ^-3 Torr, Ts=
It was produced under the condition of 150℃. 4πMs is
It showed a tendency to decrease as Vp increased.
This result shows that for Fe-N films, the short-range order of the film decreases rapidly when the deposited particle energy exceeds 30 eV (corresponding to Vp = 20 V).

The results described above can be summarized as follows.

(a) By controlling each film deposition condition independently, the dependence of the crystal structure of the Fe-N film on nitrogen partial pressure and substrate temperature becomes clear, and the film can be formed with good reproducibility.

(b) When the ion acceleration voltage Vp = 20 V, the α-Fe and γ′-Fe ₄ N phases of the obtained crystals have (110) and (200) planes strongly oriented parallel to the film plane, respectively. Ta. This is considered to be due to the high kinetic energy, uniform directionality, and charge effects of the deposited particles.

(c) The saturation magnetization 4πMs of the film has a crystal structure of α+
In the production condition region where the γ′+U.N. (Unknown) mixed phase state transitions to the γ′ single phase state, it showed a value of approximately 25KG, which is higher than pure iron.

(d) The substrate temperature at which high 4πMs can be obtained is the total pressure
The temperature decreased as Ptotal decreased, and when Ptotal was 5×10 ⁻⁵ Torr or less, the temperature was 150 to 250°C. It has been found that by increasing the proportion of ions in the deposited particles, the degree of order in the film can be improved even at low substrate temperatures.

Among these, (a) shows the good controllability of the ion beam deposition method of the present invention, and (d) shows the effect of ionization. This shows that the ion beam deposition method can be formed with good reproducibility, which proves that the ion beam deposition method is an extremely superior manufacturing method.

Furthermore, the above FexN film has sufficient corrosion resistance due to the nitrogen content, and is also excellent in this respect.

Note that the above-described example can be modified in various ways.

For example, in FIG. 3, a plurality of grids G can be set to control the ion beam in various ways. Also, there is a small hole in the lower target _T2 .
1 may not be formed, but a screen grid as described above may be arranged (vertically) laterally between both targets T ₁ and T ₂ , and the ion beam may be drawn out laterally from there. In the example in Figure 3, the
A FexN film was deposited, but instead of the substrate S, a third target _T3 was placed as shown by the imaginary line, and the ion beam ₁₀ was applied to this target T3, causing it to be ejected (spattered). Another ionized particle can be introduced onto the substrate S' together with the FexN particles, and a mixed film of both can be deposited on the substrate S'. For example, if permalloy (Ni ₈₀ Fe ₂₀ ) is used as the target T ₃ , there will be
A thin film of a mixture of FexN and permalloy is obtained.

6 Effects of the Invention As described above, the present invention comprises a base body disposed as a main pole for perpendicular magnetic recording so as to be substantially orthogonal to the magnetic recording surface of the magnetic recording medium, and a magnetically permeable layer provided on the base body. constitutes a magnetic head, and at least a part of this permeable layer is made of a mixed phase of α-Fe and γ′-Fe ₄ N or γ′-Fe ₄ N, which has a higher saturation magnetization than pure iron.
Since it is formed by the facing target sputtering method using a single phase, it has excellent high magnetization and low magnetization due to the iron nitride.
Hc, corrosion resistance can be exhibited, and a head for high performance perpendicular magnetic recording can be provided. Moreover,
Since the above-mentioned iron nitride is deposited using the facing target sputtering method, it is possible to form a film at a high deposition rate using a high-speed sputtering method, and since the substrate is not directly exposed to plasma, it can be formed at a low substrate temperature. This makes it possible to sufficiently advance crystal growth and form a film with high magnetic properties with good reproducibility.

[Brief explanation of drawings]

The drawings are for explaining the present invention, and
Figures 1 and 2 are schematic diagrams showing two examples of magnetic heads, Figure 3 is a cross-sectional view of the ion beam generator, Figure 4 is a principle diagram of opposed target sputtering, and Figure 5 is the ion beam extraction. 6 is a cross-sectional view taken along the line X-X of FIG. 5, FIG. 7 is a diagram showing the electric circuit system of the above device, FIG. The figure shows the relationship between the crystal structure of the deposited film, nitrogen partial pressure, and substrate temperature.
Figure 10 is an X-ray diffraction diagram of the deposited film, Figure 11 is a graph showing the relationship between the saturation magnetization and coercive force of the deposited film, and nitrogen partial pressure, and Figure 12 is the relationship between the saturation magnetization of the deposited film and the substrate temperature. FIG. 13 is a graph showing the relationship between the saturation magnetization of the deposited film and the acceleration voltage. In addition, in the symbols shown in the drawings, 2...Gas introduction tube, 3...Magnetic coil, 10...Ion beam, 11, 12...Small hole, 13...Anode (acceleration electrode), 14...Magnetic (chemical) membrane, T ₁ , T ₂ ...
...Target, G...Screen grid, A...
...Spatter part, B...Ion beam extraction part, S...
...It is a board.

Claims (1)

[Claims] 1. In contrast to an auxiliary magnetic pole placed on one side of the magnetic recording medium, as a main magnetic pole for perpendicular magnetic recording placed on the other side of the magnetic recording medium, a magnetic pole approximately on the magnetic recording surface of the magnetic recording medium is used. It consists of a base body arranged orthogonally to each other and a magnetically permeable layer provided on this base body, and at least a part of this magnetically permeable layer contains α-Fe and γ′-Fe, which exhibit higher saturation magnetization than pure iron. A magnetic head for perpendicular magnetic recording, which is formed by a facing target sputtering method using a mixed phase with ₄ N or a single phase of γ'-Fe ₄ N.