JPH01119008A - Formation of ferromagnetic thin film - Google Patents

Abstract

PURPOSE:To obtain a vertically magnetized film whose maximum energy product (BH)max is large by forming an alloy thin film consisting of Co and at least one kind of such rare earth metals as Sm, Pr by means of sputtering, and annealing such film whose squareness ratio in the thickness direction is at least 0.7 either in vacuum or in a nonoxide gas atmosphere. CONSTITUTION:An alloy thin film consisting of Co and more than one kind of rare earth metal Sm, Pr by means of sputtering on a substrate, and a substrate having an alloy thin film whose squareness ratio in the thickness direction is at least 0.7 is selected and annealed either in vacuum or in a nonoxide gas atmosphere within such an area as to be contoured by line Y=1000, line X=1, line Y=750, line X=6, and a line connecting between point (1,850) and point (4.55,750) when the X axis is the annealing time (log s) and the Y axis is the annealing temperature ( deg.C). The annealing time varies depending on the annealing temperature. For example, the annealing time is 10 seconds at annealing temperatures of 850-1000 deg.C. When the annealing temperature is 820 deg.C, the annealing time is 100 seconds. When the annealing temperature is 780 deg.C, the annealing time is 2500 seconds. Thus the annealing time becomes longer as the temperature decrease.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a ferromagnetic thin film used in magnetic recording media, high-performance compact morphs, etc.
This invention relates to a forming method for increasing x.

(Prior Art) SmCO5-based magnets, which have a large coercive force and a maximum energy product (BH) max, are being used more and more because they contribute to the miniaturization of devices. However.

This magnet cannot be used in thin walls or special shapes because it is difficult to form and process. Therefore, research has been conducted to form FIV films of arbitrary shapes by liquid quenching, sputtering, spraying, etc. For example, an example of the sputtering method is J. Appl.

Phys, 57 (6)15. March1982,
P, 2147-2154.

(Problems to be Solved by the Invention) When improving the performance and downsizing of devices that utilize magnetism, the maximum energy product (BH) max is large.

For example, a value of 10 MGOe or more is required,
In particular, at present, as shown in the above-mentioned literature, a film with anisotropy in the film thickness direction and a maximum energy product (BH) max exceeding the above value has not been obtained.

An object of the present invention is to provide a method for forming a film having a high maximum energy product (BH) max and anisotropy in the film thickness direction, which solves the above-mentioned problems.

(Means for solving the problem) For this purpose, after forming an alloy thin film consisting of one or more of rare earth gold fism and Pr and Co by sputtering method,
Films with a squareness ratio of 0.7 or more in the film thickness direction are heated to 750 or more in vacuum or in a non-oxidizing gas atmosphere (for example, in N2 gas).
Annealing is performed at a temperature of 1000''C for 10 seconds to 300 hours.

(Function) By annealing a film with anisotropy in the film thickness direction using the sputtering method under the above conditions, crystallization is achieved, defects and impurities are removed from the grains, and magnetic domains in opposite directions are generated. The nucleus is gone.

Therefore, even if an external magnetic field is applied, the movement of the domain walls is prevented, so that a film having a high energy product and anisotropy in the film thickness direction can be obtained.

(Example) FIG. 1 is a sectional view of a multipolar 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 distance of 25 m is set opposite to the target 2.
The substrates 3 are placed on a substrate mount 4 at intervals of m.

Base) The paper 3 can be heated by the heater 6.

The temperature of the substrate is controlled by a heater power source 13. A shutter 5 is provided between the target 2 and the substrate 3 to prevent particles scattered during the initial stage of sputtering from adhering to the substrate, and a DC voltage or high frequency voltage can be applied to the target 2 by a target electrode a7. It's Nishide. A filament 8 and an anode electrode 10 are arranged near the target, and a filament power source 9
The filament is heated to generate thermoelectrons, which are collected at the anode electrode lO.The target current can be changed arbitrarily by the filament power source 9 and the anode power source 11, so the target voltage and target current can be changed independently. be.

Kuget 2 contains 7 at% Sm, 7 at% Pr, and Co
Each powder was mixed with a composition of 86 at%.

Using a target sintered in a vacuum, this target is attached to a sputtering electrode, and the substrate 3 is placed on the substrate stand 4, and then the inside of the vacuum container is heated to 2X10-'Tor by the exhaust system 14.
Exhaust to below r. The substrate 3 is heated to 300°C while adjusting the heater power supply 13, and the filament power supply 9 is adjusted to heat the filament 8. After that, the argon gas introducing pulp 12 is opened to introduce argon gas, and the pressure is increased to 8°C.
×10-”Torr. After adjusting the anode power supply 11 to bring the target current to 0.5 A, apply a negative DC voltage of 300 V from the target power supply 7 while keeping the shutter 5 closed. Perform preliminary sputtering for 15 minutes to remove oxides etc. on the target surface.
Open the shutter and perform sputtering for 20 minutes.
A film with a thickness of μm was formed. After that, the inside of the vacuum chamber was again evacuated to 2×10''' Torr or less, and the substrate was cooled to room temperature. Among these, the squareness ratio in the film thickness direction was 0.
Select one of 7 or higher, place it in an infrared image furnace capable of rapid heating and cooling, evacuate the inside of the furnace to below 2X 10-'Torr, heat it to 900'C, and hold it for 10 seconds. After annealing, it was immediately cooled.

As a result, a ferromagnetic film with an energy product of 10 MGOe or more was obtained. Figure 2 shows the distribution of the measured values of film characteristics when annealing was performed at various temperatures and times, divided into 10 MGOe and above and below.The circles indicate the maximum energy product (BH) in the film thickness direction after annealing. max is IOMC; Oe, or more.

In other words, if annealing is performed under the conditions of the shaded area, the maximum energy product (BH) max in the film thickness direction will be 10 MGO.
e or more can be obtained. If the annealing temperature exceeds 1000°C, the magnetic properties will be impaired due to the growth of the paramagnetic phase, and conversely, if the annealing temperature is less than 750°C, Sm1CO1? It was revealed that phase precipitation causes magnetic domains in opposite directions, which lowers the coercive force.

Also, the annealing holding time varies depending on the annealing temperature. For example, when the annealing temperature is 850°C to 1000°C, the holding time is 10 seconds, but when the annealing temperature is 820°C, the holding time is 100 seconds, and when the annealing temperature is 780°C, the holding time is 100 seconds. The lower the annealing temperature is, such as 2500 seconds, the longer the holding time becomes. However, when the holding time exceeds 10 hours and the annealing temperature is between 750 and 1000°C, 10 MGOe or more can be obtained.

In addition, 5 investigations were conducted by changing the composition of the alloy thin film.

Selecting the compositions shown in the table with a squareness ratio of 0.7 or more, experiments were conducted under the annealing conditions described above, and good results were obtained in all cases. That is, Sm is 20 to 100 atomic %, Pr is O
The maximum energy product (B
H) An anisotropic film with a max of 10 M G Oe or more can be obtained.

Table (Effects of the Invention) As explained above, according to the present invention, the maximum energy product (
There is an effect that a perpendicular magnetization film with BH)max of 10 MGOe or more can be obtained, and therefore a device using magnetism can be made high-performance and compact.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a multipolar magnetron sputtering apparatus for forming a perpendicularly magnetized film of the present invention, and FIG. 2 is a characteristic diagram showing annealing conditions of the present invention. In the figure, 2 is a target, 3 is a substrate, and 5 is a shutter. 1 Figure 1, Vacuum container 7. Target electric M13. Heater electric wetting 2, target 8. Filament 14.
Scaffolding system 3, base, board q, filament power supply 4,
Board mounting stand 10. Anode electrode 5, shutter 11. Anode ffl source 6, heater 12. Alzu Shigas Introduction Bargo Figure 2 Anne Louis Kumochi Shima (Jlols)

Claims (1)

[Claims] An alloy thin film consisting of one or more of the rare earth metals Sm and Pr and Co is formed on a substrate by sputtering, and a substrate having an alloy thin film with a squareness ratio of 0.7 or more in the film thickness direction is selected and heated in a vacuum or in a non-oxidized state. In the manufacturing gas atmosphere, the annealing holding time (logs) is plotted on the X axis, and the annealing holding temperature (
℃) on the Y axis, straight line Y = 1000, straight line X =
1, straight line Y=750, straight line X=6 and point (1,850
) and a point (4,55,750).