JPH04111302A - Artificial lattice film - Google Patents

Abstract

PURPOSE:To exhibit large force rotary angle in a short wavelength, vertical magnetization and large coercive force by alternately laminating a first film made of CO1-xFex (0<=x<=0.5) and a second film made of Ru. CONSTITUTION:Thicknesses of films made of CO1-xFex and Ru are important to obtain vertical magnetization, and the magnetization is obtained in the case of 2-20 and 2-60Angstrom . Ions generated from an ion gun l are accelerated to a target to hit atoms constituting the target, and the flying atoms are deposited on a substrate S. In order to form a laminated film, the target is alternately rotated. An ion gun 2 is used to emit ions during cleaning of the substrate or during formation of a film. When acceleration energy E of the ions is 600eV or less, an artificial lattice film having a sharp boundary can be manufactured. Quartz glass is used for the substrate. In order to manufacture the laminated film, it is previously evacuated in vacuum of 4X10<-7>Torr, Ar gas (99.99% of purity) is so introduced into a main gun (ion gun l) that its partial pressure becomes 1.5X10<-4>Torr, the Ar is ionized, and the target is irradiated with the ion beam. The target is alternately rotated at the CU1-xFex and the Ru to vary them in thicknesses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a superlattice film, particularly a new superlattice film having perpendicular magnetic anisotropy.

(Prior art) Generally, a magnetic thin film that has an axis of easy magnetization perpendicular to the film surface and a Curie temperature higher than room temperature records information of several micrometers or less by irradiating it with a light beam such as a laser beam. , and can be used as a high-density magnetic recording medium.

Such recording media include polycrystalline metal thin films such as MnB1, compound single crystal thin films such as Gd1G (gadolinium iron garnet), Tb-Fe, Gd-Co, and Tb.
Examples include rare earth-iron group amorphous alloy films such as -Co and Tb-Fe-Co.

Writing is performed on polycrystalline metal thin films such as Mn old using the Curie temperature (Tc), but since Tc* is as high as about 360° C., there is a drawback that writing requires a large amount of energy. Furthermore, since it is a polycrystalline substance, it is necessary to create a thin film with a stoichiometric composition, which makes it difficult to manufacture.

Furthermore, since films such as Gd1G are formed on a GGG (gadolinium gallium garnet) single crystal substrate, there are drawbacks such as the fact that the magnetic properties are easily affected by the condition of this substrate and that it is difficult to obtain a large-area substrate.

On the other hand, rare earth-iron group amorphous alloy thin films (RE-TM films) such as GdCo and TbFe have the following advantages: a magnetic thin film of any size can be formed, composition can be easily controlled, and grain boundaries Since there is no noise, it has advantages such as a good reproduction S/N ratio, and has been actively researched in recent years. However, this RE-
TM films generally exhibit magneto-optical Faraday effect and Kerr effect (
Kerr effect) was small, C/N ratio etc. were insufficient, and corrosion resistance was poor.

On the other hand, recently, new perpendicular magnetization films such as Co/Pt/CO/
Superlattice films such as Pd are attracting attention. These are fabricated by ordinary sputtering or ultra-high vacuum evaporation, and it is known that Co, Pt, or Pd forms a perpendicularly magnetized film when the film thickness is appropriate (approximately 4 to IOA). In addition, this film has a Kerr effect of 0.0 at short wavelengths of 400 to 500 nm.
It has a large angle of 3 to 0.4 degrees and is expected to be used as a high-density magneto-optical recording medium compatible with short wavelengths.

(Problems to be Solved by the Invention) However, these artificial lattice films have a drawback in that their coercive force is as small as 1 kOe or less. Especially when created by sputtering or IBS (ion beam sputtering), the coercive force is 30
It is as small as 0 to 5000e, and even with ultra-high vacuum evaporation method, it is only 1
It was below koe. If the coercive force is small, unnecessary magnetic domains will be reversed by the applied magnetic field during recording, causing noise and making it impossible to obtain a sufficient C/N ratio.

An object of the present invention is to provide a superlattice film having a new composition that has a large Kerr rotation angle at short wavelengths, exhibits perpendicular magnetization, and a large coercive force.

[Structure of the invention] (Means and effects for solving the problem) The present invention is based on Co1
-xFeX (0≦x≦0.5) and Ru
This is an artificial lattice film characterized in that two films are alternately stacked.

In the present invention, the film thicknesses of C011Fex and Ru are important for obtaining perpendicular magnetization, and since perpendicular magnetization can be obtained in the case of 2 to 20 A and 2 to 60 A, respectively, these film thicknesses are preferable. Ru has a close-packed hexagonal crystal structure, and Co formed on it also has a hexagonal structure, making it easy to obtain perpendicular magnetization and increasing coercive force. In other words, in a superlattice film where each layer is thin, the surface magnetic anisotropy is generally larger than the bulk magnetic anisotropy, so it tends to become perpendicular magnetization, but as the Co film thickness increases, in-plane magnetization tends to occur. Since the bulk magnetic anisotropy that causes magnetization increases, perpendicular magnetization becomes difficult to occur. On the other hand, in the case of a hexagonal crystal structure, the bulk anisotropy also tends to cause perpendicular magnetization, so Co
It is thought that perpendicular magnetization is likely to occur over a wider range of film thickness.

This artificial lattice film can be formed using many film forming methods such as normal DC/RP sputtering, ion beam sputtering, vacuum evaporation, and MBE.

(Example) Hereinafter, the present invention will be explained in detail using Examples.

An artificial lattice film having the composition system and film thickness shown in Table 1 was created using ion beam sputtering.

FIG. 1 is a schematic diagram of an ion beam sputtering (IBS) apparatus. The ions generated by the ion gun (1) are accelerated and irradiated onto the target, and the atoms constituting the target are thrown off, and the thrown off atoms are deposited on the substrate (S). To produce a laminated film, the targets are rotated alternately. The ion gun (2) is used to irradiate ions during substrate cleaning and film formation.

If the acceleration energy of the ions is too large, the energy of the atoms that make up the repelled target will also be large, and as a result, atoms will easily move on the substrate, causing mixing of atoms in the laminated film, resulting in sharp interfaces. This makes it difficult to obtain an artificial lattice film.

As a result of various experiments, it was found that a superlattice film with a sharp interface can be produced when the acceleration energy E is 600 eV or less.

The following experiment was conducted at E-500 eV. The substrate is made of quartz glass and is made of Ru and 001-xFe.
A laminated film was prepared by rotating the target using each target.

After evacuating to a vacuum level of 4 x 10''''7 Torr in advance, inject A gas (purity 99.99%) into the main gun (ion gun 1).
) was introduced until the partial pressure reached 1.5 x 10-'Torr, ionized Ar, and irradiated the target as an ion beam. The target is CO1□ every predetermined time.
An artificial lattice film was produced in which Fe x and Ru were alternately rotated to change the thickness of each film. Below, C00-xF
The film thickness of ex is T, the film thickness of Ru is R, and the number of repetitions of Co1-xFe- and Ru layers is n, and this superlattice film is (T/
R) It will be expressed as n.

Table 1 shows the Kerr rotation angle of each superlattice film (wavelength 400na+
) and the coercive force value determined from the perpendicular magnetization curve.

This shows that the superlattice film of the present invention has a larger coercive force than the Co/Pt superlattice film (comparative example).

Part 1 table [Effect of the invention] As described above, the superlattice film of the present invention has a large coercive force.

Since the Kerr rotation angle is large at short wavelengths, it is useful as a new magneto-optical recording medium. Note that the hexagonal Co film is made of Ti, Zr
, Hr, Re, etc., and a laminated film of these metals and Co is also effective.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for producing the artificial lattice film of the present invention.

Claims (1)

[Claims] An artificial lattice film characterized in that a first film made of Co_1_−_xFe_x (0≦x≦0.5) and a second film made of Ru are alternately laminated.