JPH0565043B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for forming a crystalline perpendicular magnetization film used in a perpendicular magnetic recording medium suitable for high-density recording. [Conventional technology] Conventionally, thin films for perpendicular magnetic recording have generally been manufactured by using surface treatment techniques such as sputtering, vacuum evaporation, or chemical plating for Co-Cr alloys. Ta. It also has a composition represented by R _X M _(1-X) , where R is
One or more types of Nd, Yb, M is one or more types of Fe, Co,
A magnetic recording medium made of an amorphous magnetized film in which x is 0.1 to 0.4, and if necessary, B, Bi,
A magnetic recording medium has been proposed in which an amorphous film and a magnetized film are added with a very small amount of Si or Zr of 0.1 mole or less. (Unexamined Japanese Patent Publication No. 60-128606) [Problems to be Solved by the Invention] However, chromium Cr, which is an evaporation source, is undesirable because it is harmful to the human body, and cobalt Co is expensive. Further, although an amorphous magnetized film has the advantage of good writing sensitivity, it has the disadvantage that the vertical direction becomes unstable due to temperature changes after it is formed, and there are problems in terms of quality and durability. [Purpose of the invention] Therefore, this invention uses harmless neodymium without using Cr and expensive Co, which are harmful to the human body.
The object of the present invention is to provide a perpendicularly magnetized film with a crystalline structure consisting of Nd, iron (Fe), and boron (B). [Means for Solving the Problem] Therefore, as a result of various experiments, the present inventor used an alloy consisting of the elements neodymium Nd, iron Fe, and boron B, and the atomic concentration was Nd _X Fe _{(100- xy)} By, where x is 13 to 27 and y is 3 to 17, the deposition rate (μm/min) and substrate temperature (°C) are (0.05, 420) and (0.05). , 400), (1.0
,
A good crystalline perpendicular magnetization film could be obtained by sputtering within the range surrounded by the straight line connecting the four points 100) and (1.0, 600). [Effect] In this way, by forming a thin film mainly composed of Nd, Fe, and B, and setting the sputtering conditions within a certain range, fine crystals grow in the film thickness direction, and the axis of easy magnetization changes. A crystalline perpendicular magnetization film aligned in the film thickness direction can be obtained. [Example] FIG. 1 shows a cross-sectional view of a magnetron sputtering apparatus for forming a perpendicularly magnetized film of the present invention. A target 2 is provided in a vacuum container 1, and a substrate 3 is placed inside the vacuum container 1.
is placed on the board mount 4, facing the target at a distance of 40 mm. The substrate 3 can be heated by a heater 6, and the temperature of the substrate is controlled by a heater power source 9. A shutter 5 is provided between the target 2 and the substrate 3 in order to prevent particles scattered during the initial stage of sputtering from adhering to the substrate. A DC voltage or a high frequency voltage can be applied to the target 2 by a target power supply 7, and by changing this voltage, the speed of adhesion to the substrate can be adjusted. The perpendicular magnetization film was formed in the following steps. Target 2 obtained by mixing Nd powder, B powder, and Fe powder and sintering in vacuum so that the atomic percent of neodymium in the thin film is 15% and the atomic percent of boron is 5% is sputtered with an electrode. After mounting the substrate 3 on the substrate mount 4, the vacuum container 1 is evacuated to 2×10 ^-6 Torr or less by the exhaust system 10.
After heating the substrate 3 to 300° C. while adjusting the heater power supply 9, the argon gas introduction valve 8 was opened to introduce argon gas, and the pressure was adjusted to 3×10 ⁻² Torr. With the shutter 5 kept closed, a negative DC voltage of 400 V was applied from the target power supply 7, and preliminary sputtering was performed for 15 minutes to remove oxides on the target surface. Next, open shutter 5 and
Sputtering was performed for 60 minutes to form a film of about 5 μm on the substrate surface. After this film was formed, the inside of the vacuum chamber 1 was evacuated to 2×10 ^-6 Torr or less, and the substrate was cooled to room temperature. After cooling, we measured the magnetic properties of the thin film attached to the taken out substrate 2, and found that the second
The magnetization curve shown in the figure was obtained. This magnetization curve shows that the perpendicular direction is the axis of easy magnetization. However, the magnetization curve 20 is perpendicular to the film surface, the magnetization curve 21 is the magnetization curve when a magnetic field is applied in the plane, and the demagnetization curve 20 is not corrected by the demagnetizing field. Further, as a result of examining the X-ray diffraction pattern, it was confirmed that the C axis was oriented perpendicular to the film surface. Films were formed by changing the substrate temperature and deposition speed using the same procedure, and the sputtering conditions for obtaining a perpendicularly magnetized film were investigated, and the results shown in FIG. 3 were obtained. The range A surrounded by the broken line in FIG. 3 is the condition under which a perpendicularly magnetized film was obtained. As the deposition rate increases, the heating due to the power increases, but the range of substrate temperatures at which a perpendicularly magnetized film can be obtained becomes wider. Conditions other than range A, for example, when the substrate temperature is low, the crystal structure becomes amorphous and satisfactory magnetic properties cannot be obtained, and conversely, when the substrate temperature becomes high, the crystal grains become coarse and the vertical orientation becomes poor. is lost. The saturation magnetic flux density Bs of the perpendicularly magnetized film formed within the range of A was a large value of 6000 Gauss or more, and the coercive force Hc was about 600 Oersteds, so that practically sufficient characteristics as a magnetic recording medium were obtained. Next, the composition of the alloy thin film was varied by varying the composition of the target, and the thin alloy film was formed under the sputtering conditions of range A and examined. As a result, a perpendicularly magnetized film was formed with the composition shown in Table 1, and the magnetic properties described above were obtained. That is, when the film composition was expressed as Nd _x Fe _(100-xy) By, x was in the range of 13 to 27 and y was in the range of 3 to 17.

【table】

[Table] [Effects of the Invention] As explained above, according to the present invention, crystals containing neodymium, iron, and boron as main components and by setting sputtering conditions within a certain range are harmless to the human body and resistant to aging. This has the effect of making it possible to obtain a high-quality perpendicularly magnetized film at a low cost, making it possible to apply it to high-density magnetic recording media.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnetron sputtering apparatus for forming a perpendicularly magnetized film of the present invention, and FIG.
This figure shows the magnetization curve of a perpendicularly magnetized film obtained by a typical method of the present invention, and FIG. 3 shows the range of sputtering conditions for obtaining a perpendicularly magnetized film. 1 is a vacuum container, 2 is a target, 3 is a substrate, 4
5 is a shutter, 6 is a heater, 7 is a target power supply, and 9 is a heater power supply.

Claims (1)

[Claims] 1. In an alloy film consisting of the elements neodymium Nd, iron Fe, and boron B, the atomic concentration is expressed as Nd _X Fe _(100-xy) By, where x is 13 to 27 and y is 3. An alloy thin film with values of ~17 was deposited under conditions of deposition rate (μm/min) and substrate temperature (℃) of (0.05, 420), (0.05, 400), and (1.0).
,
1. A method for forming a perpendicularly magnetized film, which comprises forming a perpendicularly magnetized film in a crystalline state by sputtering in an area surrounded by a straight line connecting four points (100) and (1.0, 600).