JPH0227806B2 - KOHOWAJIKAJISEIZAIRYOOYOBISONOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

The invention of this application relates to a magnetic material containing a large amount of Fe ₁₆ N ₂ and a method for producing the magnetic material by sputtering. Pure iron is the most basic material in the field of magnetic materials.
It exhibits relatively high magnetic permeability and high saturation magnetization (σ _s
= 218 emu/gr, M _s = 1717 gaues), so it is used for magnetic cores and contacts of relays and electromagnets, and yokes for magnetic circuits, but Fe ₁₆ N ₂ , which is an iron nitride, is As shown in Table 1, it has higher saturation magnetization than the pure iron mentioned above (saturation magnetization per unit weight σ _s = 298 emu/gr, saturation magnetization per unit volume M _s = 2200 gauss). T _c indicates the Currie point. However, even with the same nitride, Fe ₄ N exists as an impurity in pure iron, and as shown in Table 1, it significantly deteriorates the magnetism.

[Table] In the production of iron nitride, suppressing the generation of Fe ₄ N,
No effective technology for producing a large amount of Fe ₁₆ N ₂ has conventionally existed, and only attempts have been made to produce Fe ₁₆ N ₂ by vacuum evaporation in an N ₂ atmosphere. However, even with this vacuum evaporation, there is only a slight reaction with N ₂ and the evaporation rate is extremely slow.
Since it could only be made as ultra-thin as 100 Å, it was far from suitable for industrial use. The present invention has been made in view of this point, and includes a magnetic material formed by reactive sputtering in a nitrogen-containing atmosphere using pure iron as a target, the magnetic material having a thickness of 1 μm or more, and more than 10% by weight in magnetic materials based on pure iron.
A high saturation magnetization magnetic material characterized by containing Fe ₁₆ N ₂ iron nitride and a substrate temperature of 300°C or less,
Pure iron-based high saturation magnetization magnetic material containing a large amount of Fe ₁₆ N ₂ iron nitride is manufactured by performing reactive sputtering in a nitrogen and argon gas atmosphere with a nitrogen partial pressure (PN ₂ ) of 1×10 ^-3 Torr or less. Regarding how to. As a result, a magnetic material with excellent magnetic properties can be obtained, and the manufacturing speed has also been significantly increased, making it possible to manufacture a high-performance magnetic material at low cost. recent years,
With the increasing demand for high-density recording, Co-Ni Binder-free magnetic recording media in which a magnetic recording layer is a ferromagnetic metal thin film such as Co--Cr are attracting attention, and some of them have been put into practical use. In order to further increase the recording density, magnetic thin film materials with high saturation magnetization and coercive force are required, so research is focused on Fe-based alloys, Co-based alloys, and Ni-based alloys. Fe ₁₆ N ₂ , which is the iron nitride of the present invention, has a saturation magnetization higher than that of pure iron, as shown in Table 1, and is promising as a material for magnetic recording media. That is, by forming a thin film of iron nitride on a nonmagnetic substrate, a recording layer with much higher saturation magnetization and coercive force than conventional materials can be obtained, making it possible to increase magnetic recording density. The iron nitride-containing magnetic material of the present invention can also be used as a magnetic medium material. When producing nitrides by reactive sputtering, it is necessary to introduce nitrogen gas in addition to argon gas to create a mixed gas atmosphere of argon gas and _nitrogen . )
Must be less than 1×10 ^-3 Torr. Generally, we tend to think that the higher the nitrogen partial pressure (P _{N2 )} , the faster the nitride formation rate, and therefore the production of a large amount of Fe ₁₆ N ₂ , but if the nitrogen partial pressure (P _N2 ) is 1×10 ^- When the temperature exceeds ³ Torr, the generation of Fe ₄ N, etc. increases, and the generation of Fe ₁₆ N ₂ stops. The present invention has focused on this point among many attempts, but it is common knowledge that it would be unthinkable to lower the nitrogen partial pressure P _N2 to a lower pressure side in the production of such nitrides. It is. A more effective range of P _N2 is 2 to 7×10 ⁻⁴ Torr, and if it is lower than 2×10 ⁻⁴ Torr, the saturation magnetization will be lower than that of pure iron. Furthermore, as described later, Fe ₁₆ N ₂ is decomposed by heating. In particular, at temperatures exceeding 250 to 300°C, it changes to Fe ₄ N, which has poor magnetic properties. During the sputtering operation, the substrate is heated by radiant heat from the filament and the temperature of the substrate also increases, so the change from Fe ₁₆ N ₂ to Fe ₄ N also occurs during the sputtering operation. Therefore, in order to suppress this, the substrate temperature should be
It is necessary to keep the temperature below 300℃. A more effective range for this substrate temperature is 200°C or less. As described above, by adjusting the nitrogen gas partial pressure P _N2 and selecting the critical conditions of the substrate temperature, it became possible for the first time to produce iron nitride containing a large amount of Fe ₁₆ N ₂ . As explained in the example below, when sputtering is performed on a glass substrate on a water-cooled steel plate, a thickness of approximately 3 μm is obtained.
Fe ₁₆ N ₂ -containing magnetic material is produced, but thicker magnetic material can be formed by increasing the cooling rate and sputtering rate can also be increased. A magnetic material having such a shape can be used industrially. Furthermore, in order to obtain good properties exceeding the saturation magnetization of pure iron, it is necessary that at least 10% by weight of Fe ₁₆ N ₂ be present in the sputtered magnetic material. The magnetic material components other than Fe ₁₆ N ₂ are mainly pure iron, but other nitrides, such as Fe ₄ N
It is unavoidable that such substances are contained to an extent that does not deteriorate the magnetic properties. By implementing the present invention under the above conditions,
Magnetic materials containing a large amount of Fe ₁₆ N ₂ have saturation magnetization that exceeds that of pure iron. Next, an example will be described. Example Using pure iron as the target and glass as the substrate, the deposition speed was set to approximately
The rate was 500 to 1000 Å/min. The glass substrate was set in a copper holder, and the copper holder was cooled with water so that the substrate temperature was below 300°C. The nitrogen gas partial pressure during sputtering was controlled by the following two methods. 1 A method using two cylinders for argon and nitrogen, each controlled by a flow rate adjustment valve. 2. A method that uses a mixed gas cylinder with a preset pressure ratio of argon and nitrogen (for example, 99:1) and controls it with a single flow control valve. The experiment was carried out at a target voltage of 0.5 KV and a current density of 4 mA/cm ³ . Figure 1 shows the nitrogen partial pressure during sputtering.
The relationship between P _N2 and saturation magnetization σ _s is shown. The magnetic material is 3 μm thick. P _N2 1×10 ^-3 Torr or less, especially
σ _s higher than that of pure iron, 218e.mu/gr, was obtained near P _N2 4.0×10 ^-4 Torr. Next, the results of thermomagnetic analysis are shown in Figure 2. ●-● are the heating curves of the magnetic material of the present invention, and △-△ are the heating curves of pure iron. Before heating, the magnetic material σ _s of the present invention is larger than that of pure iron, σ _s =218 emu/gr. As is clear from this heating curve, magnetization decreases at about 200°C. This is considered to correspond to the Kyrie point of Fe ₁₆ N ₂ . If heating continues further and the temperature exceeds 300℃, there is a tendency for σ _s to decrease compared to that of pure iron. Furthermore, there is a clear decrease in σ _s near 480°C, but this is the Curie point of Fe ₄ N, where σ _s decreases significantly. As is clear from the above, the magnetic material of the present invention has σ _s , that is _, saturation magnetization, which is superior to the σ _s of pure iron _. This means that it is present in large quantities. Furthermore, according to the above heating curve, Fe ₁₆ N ₂
It was found that the saturation magnetization becomes lower than that of pure iron at the stage of changing to Fe ₄ N.
It becomes clear that the temperature should be maintained at ℃ or below, more preferably 200℃ or below.

[Brief explanation of drawings]

Figure 1 shows nitrogen partial pressure (P _N2 ) during sputtering.
Graph showing the relationship between and saturation magnetization at room temperature, 2nd
The figure is a graph showing the relationship between the saturation magnetization σ _s and the heating temperature according to thermomagnetic analysis of the sputtering film obtained in the present invention.

Claims (1)

[Claims] 1. High saturation magnetization characterized by having a thickness of 1 μm or more and containing 10% by weight or more of Fe ₁₆ N ₂ iron nitride in a magnetic material based on pure iron. magnetic material. 2 Keep the substrate temperature below 300°C and reduce the nitrogen partial pressure (PN ₂ ).
By performing reactive sputtering in a nitrogen and argon gas atmosphere below 1×10 ^-3 Torr.
A method for producing a pure iron-based highly saturated magnetized magnetic material containing a large amount of Fe ₁₆ N ₂ iron nitride. 3. The method according to claim 2, wherein the substrate temperature is 200°C or less. 4. The method according to claims 2 and 3, characterized in that the nitrogen partial pressure (PN ₂ ) is 2 to 7×10 ⁻⁴ Torr.