JP2612966B2 - Amorphous uranium alloy, magneto-optical storage medium and magneto-optical storage system using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an amorphous uranium alloy exhibiting high magneto-optical properties. Further, the present invention provides a storage medium, an optical modulator,
The use of such amorphous uranium alloys for purposes such as optical insulators. Specifically, the amorphous uranium alloy of the present invention contains antimony and further contains an auxiliary alloy such as manganese or cobalt. The amorphous alloys of the present invention are particularly suitable as magnetic storage media for beam-addressable files.

BACKGROUND OF THE INVENTION Beam addressable files using insulating magnetic thin films are known in the art. For example, materials such as gadolinium iron garnet have been used. Also
Metals such as MnBi have also been used as storage media in beam addressable files. A general description of these file systems can be found below.

1.AH Eschenfelder, J.APP
L.PHYS., 41,1372 (1970) 2.JA Reichman (Rajchman), J.APPL.PHYS., 41,137
6, (1970) 3. RE McDonald et al., J. APPL. PHYS., 40,
1429 (1969) 4. D. Chen et al., J. APPL. PHYS., 39, 3916 (1968)
In addition to these materials, a stoichiometric composition of MnAlGe has been proposed as a suitable material in the field of magneto-optics. This is a polycrystalline film.

As can be seen by reference to US Pat. No. 3,530,441, some non-magnetic amorphous materials have been used in beam addressable files. These amorphous materials are "ovonic" materials that exhibit no magnetic properties and, unlike switching that occurs in magnetic films, undergo structural changes when switching in a beam-addressable environment. Structural changes (transition between amorphous and crystalline states) are much more destructive to the film itself, so in this type of environment magnetic films can switch many times more than amorphous non-magnetic films.

Amorphous films have the advantage that they can be placed on any type of substrate and can be adjusted to provide a wide range of compositions. In addition, there is no requirement for polycrystalline grain size that exists with crystalline beam-addressable storage material.

More recently, amorphous materials suitable as magnetic media, such as in a beam-addressable file environment, have been assigned to International Business Machines Corporation, U.S. Pat.
No. 3,963,463. These disclosures are incorporated herein by reference.

However, while the amorphous materials disclosed in U.S. Pat. Nos. 3,949,487 and 3,965,463 exhibit magneto-optical properties suitable for their desired use, they did not withstand improvements in certain properties. For example, to facilitate reading from a file, it may be desirable to increase the degree of Faraday rotation. Other properties needed to make a material useful as a magnetic medium in a beam-addressable system include the atomic magnetic moment, spin-orbit coupling, magnetic order,
There is a magneto-optical response at the desired wavelength, a square hysteresis loop, and the like. Thus, it is clear that it is very difficult to find a material that can meet the requirements for beam addressable magnetic storage media.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a material that is suitable as a magnetic medium and that exhibits a large magneto-optical rotation (Faraday rotation or magneto-optical Kerr rotation) as compared with conventional amorphous magnetic materials. Another object of the present invention is to provide a material having a magnetic moment, spin orbit coupling, magnetic order, responsive to light, and having a square hysteresis loop.

Specifically, the present invention relates to uranium-containing amorphous alloys exhibiting a magneto-optical rotation having a Faraday rotation of at least 0.9 × 10 ⁶ degrees / cm or a magneto-optical Kerr rotation of at least about 1 degree.

Another embodiment of the present invention is an amorphous uranium alloy that includes uranium and antimony and exhibits an auxiliary alloy, such as manganese or cobalt, that exhibits magneto-optical rotation. The atomic ratio of uranium to antimony is preferably
60:40 to 40:60.

Another aspect of the present invention is to use the above amorphous alloy as a magnetic storage medium in a storage system.
An electromagnetic beam is applied to locally heat a storage medium included in the storage system, and a plurality of information bits are written on the storage medium, or information related to the bits stored in the storage medium is transmitted using a light beam. read.

Another aspect of the invention is a magnetic system comprising a magnetic medium comprising an amorphous alloy of the type described above, writing means for changing the magnetic state of the magnetic medium, and reading means for detecting the magnetic state of the magnetic medium. . Writing means, beam generating means for applying electromagnetic energy to the magnetic medium,
A magnetic field generating means for generating a magnetic field in the magnetic medium is provided.

Another aspect of the present invention is directed to a beam addressable system with a magnetic medium comprising an amorphous alloy of the type described above. The beam addressable system also includes beam generating means for generating a beam of electromagnetic energy at a desired location on the magnetic medium to heat the magnetic medium. The beam addressable system also includes magnetic field generating means for generating a magnetic field in the magnetic medium to change its magnetic state at a desired location. A reading means for detecting a light beam hitting the magnetic medium at a desired position and determining the magnetic state at that position is also included.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a beam addressable file system using an amorphous magnetic film as a storage medium.

FIG. 2 shows a beam addressable file system with amorphous magnetic material on a moving disk.

FIG. 3 is a diagram showing an apparatus for reading information stored in an amorphous magnetic film using the Kerr effect.

FIG. 4 is a diagram showing a magneto-optical light modulator using the amorphous magnetic material as a light modulation medium.

FIG. 5 is a diagram showing a tape or disk information processing system using the amorphous magnetic material of the present invention as a recording medium.

FIG. 6 and FIG. 7 are graphs showing the energy dependence (10 ⁶ degrees / cm) of the intrinsic Faraday rotation.

FIGS. 8 and 9 are graphs showing Faraday hysteresis loops at various temperatures.

FIG. 10 is a graph showing the temperature dependence of Faraday rotation in a magnetic field of 1 kOe.

The 11A view and a 11B Figure is a graph showing the temperature dependence of the Faraday rotation theta _F of the four compositions were A) measured, and B) the temperature dependence of the Kerr rotation theta _K of measured five compositions .

FIG. 12 shows the composition U _0.48 S at a temperature of 10 K, 20 K, 50 K, 80 K
is a graph showing the magnetic field dependence of H Faraday rotation theta _F of b _0.52.

FIG. 13A and FIG. 13B is a graph showing the energy dependence of the Faraday rotation theta _F of the four compositions, and B) the energy dependence of the Kerr rotation theta _K of the four compositions.

FIG. 1 shows a beam-addressable file system having a film 10 of amorphous magnetic material on a suitable substrate 12. Substrate 12 may be an insulator or a conductor, and may transmit or reflect input electromagnetic energy. Examples of suitable substrates, glass, spinel, quartz, sapphire, Al ₂ O _3, and metal such as aluminum or copper. An energy source 14 is provided, which is typically a light source. Energy source 14 is preferably a laser on a laser array that produces a monochromatic output beam. The present invention utilizes any electromagnetic energy source or any other energy source that can supply energy of sufficient strength to heat the amorphous magnetic film 10 to its compensation temperature or near the Curie point _Tc. it can. That is, a part of the film 10 can be locally heated during the writing operation and the erasing operation using the electron beam.

An electromagnetic energy source 14 is associated with a polarizer 18 and a focusing lens 20. Polarizer 18 is of the type that provides a plane-polarized beam, as is well known in the art.

An optical modulator 22 for changing the intensity of the light beam 16 is provided. This special mechanism is used to read information from selected portions of the membrane 10, as will become more apparent later. Light deflector 24 deflects light beam 16 so that it impinges on selected discrete portions of film 10. Optical deflector 14
May be of a known type, for example a photoelectric deflector that deflects the beam 16 to a selected portion of the film 10 in response to the application of an electric field to the deflector 14. Acoustic deflectors are also suitable. Of course, in the case of an electron beam input, a magnetic element or an electrostatic deflection element is used to deflect the electron beam to a selected portion of the film 10.

Attached to the membrane 10 is a current carrying coil 26, which is used to generate a magnetic field in the membrane 10. This electric field is used to write information to the film 10 and will be described in detail when writing, reading and erasing operations are discussed later.

For reading, a lens 28 is used to focus the light beam 16 that has passed through the film 10 and the transparent substrate 12. The analyzer 30 determines the degree of rotation of the polarization vector of the light beam 16,
The light beam 16 is selectively passed. Detector 32 responds to the intensity of the light beam incident thereon and generates an electrical signal in a manner well known in the art.

For example, detector 32 may be a phototube, photodiode, or any other photosensitive element that produces an electrical output. Generally, detector 32 is a high frequency response detector.

The electrical output of the detector 32 is amplified by an amplifier 34 and applied to a utilization means 36. Means 36 for responding to the information status of the beam addressable file system,
It can be any other circuit or device.

The amorphous alloy used according to the invention contains uranium and exhibits magneto-optical rotation. Typically, the alloy can include N, P, As, Sb, Bi, S, Se, Te, Po, while the uranium alloy of the present invention includes Sb. The atomic ratio of uranium to antimony in the alloy is usually from about 15:85 to about 85:15, and from about 20:80 to about 80:20.
Preferably, about 60:40 to about 40:60 is most preferred.

Further, the amorphous alloy includes auxiliary alloys such as manganese and cobalt. Further, a mixture of the above elements can be optionally included. The amount of auxiliary metal is about 5 to 40 atomic% of the alloy, preferably about 10 to 20 atomic%.

In addition, other materials can be alloyed with uranium if the desired magneto-optical properties are obtained instead of or in addition to the alloying metals described above. It is believed that the above properties are obtained when the uranium atoms in the alloy are surrounded by a mass of atoms of the alloying metal, separating the uranium atoms and thereby generating a magnetic moment.

According to a preferred embodiment of the present invention, the amorphous uranium alloy exhibits a Faraday rotation of at least about 0.9 × 10 ⁶ degrees / cm, more preferably at least about 10 ⁶ degrees / cm, Most preferably, it is at least about 2 × 10 ⁶ degrees / cm. Correspondingly, the Kerr rotation of the amorphous uranium alloy is preferably at least about 1.6 degrees, and most preferably at least about 3 degrees.

The Faraday rotation and Kerr rotation achieved by the present invention are very surprising. None of the conventionally known amorphous magnetic materials has such a high value.
Specifically, the maximum rotation for amorphous alloys reported to date has been about 0.5 × 10 ⁶ / cm for certain Nd alloys. Furthermore, there are only a few crystalline materials that exhibit such high rotation, such as EuS and CeSb. Although crystalline uranium compounds with large Kerr rotations have been reported (eg, W. Reim, J. Magn. Magn. Mat. 58, 1 (1986)
)), The materials are not available in thin film form (the Lime article above discusses a cleaved mirrored single crystal containing USb with a rock salt structure), and this single crystal uranium compound is Has a magnetic crystal anisotropy large enough to saturate only along a certain crystal direction in a magnetic field of
It has no meaning as a magnetic storage medium. That is, the polycrystalline film is not very useful because most crystallites are not oriented so that the axis of easy magnetization is in the direction of light propagation. In addition, the magneto-optical properties achieved by the alloys of the present invention are quite surprising, since many amorphous uranium alloys, especially amorphous alloys of uranium with rare earth or transition metal elements, are not magnetic. UCo, UFe, UTb, UYb,
Combinations such as UGd, UNi have also been studied, but have been found to contain non-magnetic U, unlike the alloys of the present invention. Uranium in these alloys had no magnetic moment and did not show high Faraday rotation.

The amorphous uranium alloy of the present invention has at least about 100 emu
/ cm ^3, preferably an magnetization about 170~240emu / cm ³ (M), and most preferably about 175~190emu / cm ^3.

Furthermore, the amorphous uranium alloys of the present invention exhibit a square hysteresis loop, and therefore remain magnetic after being magnetized and have large magnetic resonance. This square loop characteristic guarantees long-term stability.

The amorphous uranium alloy of the present invention has at least about 5 kOe,
It preferably exhibits a coercive force (Hc) of about 10-20 kOe. The coercivity of a magnetic material is a primary factor in determining the stability of magnetic domains used to store information in a material.

It should be noted that in these materials, a high coercive force is obtained when a magnetic field parallel or perpendicular to the film surface is applied.

The amorphous uranium alloy of the present invention has at least about 70K,
It typically exhibits a Curie temperature (Tc) of about 135 ° K.

Furthermore, amorphous uranium alloy of the present invention is about 4 degrees least, preferably has a hole angle of about 10 to 17 degrees (theta _H), typical value is about 13 degrees.

In addition, this amorphous uranium alloy contains at least about 20
It exhibits a relatively large resistivity (ρ) of 0 μohm · cm, preferably about 300 to 500 μohm · cm, and at least about 40 μohm · c.
m, preferably a Hall resistivity (ρ
_H ).

The amorphous uranium alloy of the present invention is responsive to light, especially to light in the visible light range.

The amorphous magnetic material used according to the invention can be manufactured in bulk form and preferably as a thin film. Generally, any known film deposition technique can be used, including sputtering and evaporation.

Splat cooling is a useful technique for making bulk amorphous magnetic materials. In this method, when a hot liquid of the film composition is applied to a cooling surface, the composition solidifies to form an amorphous bulk film. This allows rapid cooling from the liquid phase.

In a preferred technique, an amorphous film is created by spinning a substrate, such as glass, and performing magnetron sputtering thereon. Sputtering uses two magnetron sputtering guns (one for each target), such as those marketed under the trade name Research S-gun by Sputtered Films. Uranium
This is performed separately from the target and an alloy-forming metal (eg, Sb). The target is typically placed in an atmosphere of about 3 millitorr of argon. The reference pressure is at least about 10 ^-8 torr, typically about 7 x 10 ^-8 torr. Argon is introduced at a flow rate of about 30 sccm. With the rotating substrate placed above the target, sputtering is performed at room temperature upwards from about 7.6-10 cm from the gun. When uranium and an alloy-forming metal (eg, Sb) are sequentially deposited, a homogeneous alloy is formed on the substrate. In a typical example, the substrate spins at 17 revolutions per minute, with uranium depositing about 300 angstroms per minute, for example, antimony depositing about 500 angstroms per minute. Prior to deposition, the substrate can be cleaned, for example, by washing in a typical detergent and then with deionized water. The amorphous alloy is coated with _{SiO 2, ZrO 2, TiO 2} , Si 3 N 4 or other transparent coatings can be protected from oxidation.

Operation of the System of FIG. 1 Information is written to the storage film 10 using Curie point writing or compensation point writing. Reading is performed using the Kerr effect or the Faraday effect. Clear individual positions or sheets
Block erasure of the entire 10 can be performed easily.

Write Operation The steps required to generate information in a selected area of the amorphous magnetic sheet 10 are the same whether using Curie point writing or compensation point writing. Writing can be easily performed at liquid nitrogen temperature. This is acceptable in applications such as isolators for laser gyros and media for high performance magneto-optical disks. The compensation point is the temperature at which, for a particular composition, the opposite polarity atomic magnetic moment of each component of the composition cancels out and exhibits zero magnetization.

The writing operation in either the Curie point writing or the compensation point writing is as follows.

1. The storage film 10 is initially in a demagnetized state in which the number of magnetic domains whose magnetization is in the opposite direction and perpendicular to the film plane is approximately equal. Next, a saturation bias magnetic field perpendicular to the film plane is applied to the storage film 10 to magnetize all magnetic domains in one direction. This is easily accomplished by passing a current through the coil 26.

2. Thereafter, a small bias magnetic field in a direction opposite to a saturation magnetic field perpendicular to the plane of the film 10 is applied to the entire film. This small magnetic field is also advantageously provided by passing a current through the coil 26. If desired, the film can be scanned with a permanent magnet to generate a large saturation bias field.

3. The laser beam 16 is then applied to the selected location of the film 10 to locally heat the film to a temperature above the compensation temperature (compensation point writing) or near the Curie point Tc (Curie point writing). A small magnetic field remains on the magnetic film 10. When the laser pulse is removed, the portion of the film 10 that is struck by the laser beam cools in the presence of a small magnetic field,
The magnetization of that part switches in that direction.

In some cases, if sufficient magnetic open paths (demagnetization fields) exist in the film 10 to cause reverse magnetization, a small magnetic field need not be present during cooling of a localized area of the film.

Both Curie point writing and compensation point writing are used to bring local regions of the film into a reverse magnetization state.

Reading Operation To read the information contained in the recording spot (eg, 38) of the film 10, it is convenient to use the magneto-optical Kerr effect or the Faraday effect. For this purpose, the same light beam 16 used for writing can be used. However, when the incident beam hits the storage medium 10, the intensity of the light beam is reduced to about one-tenth of that used for writing so that no appreciable temperature rise occurs.

During a write operation, modulator 22 advanced beam 16 unimpeded to spot 38 of the film. Therefore, the film was quickly heated to a temperature near the Curie point or compensation point.
However, during a read operation, the modulator 22 causes the intensity of the beam 16 that reads the spot 38 to be about one-tenth of that used for writing.
To reduce.

When the read beam 16 hits the recording spot 38, the plane of polarization of the transmitted light beam rotates according to the orientation of the magnetic vector of the recording spot. As used herein, when the polarization direction of the beam rotates in a direction corresponding to the alignment of the antiparallel magnetic vectors, the analyzer 30 allows the light beam to pass and the polarization direction rotates in a direction corresponding to the alignment of the parallel magnetic vectors. It is assumed that the light beam is interrupted when this is done. Therefore, the strength of the signal generated by the detector 32 will indicate the magnetization direction of the recording spot 38 during reading.

Erasing Erasing can be performed locally or over the entire recording medium 10. Local erasure occurs when new information is being written to discrete portions 38 of film 10. Furthermore, local erasure occurs when the local spot is irradiated with the laser beam 16 and then cooled in the presence of a small magnetic field in the direction of the initially applied saturation field. Thus, its operation is similar to a write operation, except that a small magnetic field causes the local spot to return (or stay) to its original magnetization direction.

Block erasure is performed by applying a large bias magnetic field in the direction of the original saturation magnetic field. No laser beam is required for block erasure.

FIG. 2 shows that the storage film 10 is on the disk-shaped substrate 12,
4 shows an embodiment of a beam addressable file. For ease of explanation, use the same reference numbers where possible.
A laser array 14 or individual lasers are used to provide a light beam 16 for reading and writing information to selected portions 38 of the amorphous magnetic film 10. As in FIG. 1, polarizer 18 produces a plane-polarized light beam, and analyzer 30 is used to pass or block light of the selected polarization direction during a read operation. Detector 32 responds to the light striking it,
It is used to generate an information state electrical signal at a selected portion 38.

Laser array 14 has an associated intensity control circuit 40 that is used to modulate the intensity of laser beam 16 or during read and write operations. The intensity control circuit 40 can be, for example, a circuit that reduces the bias current to the injection lasers in the array, or a modulator within the laser cavity itself. The disk drive means 42 is used to rotate the disk containing the film 10 and the substrate 12 in the direction of arrow 44. Thus, by generating the input beam 16 using a stationary laser or laser array, selected portions of the membrane 10 are addressed. As before, the energy source 14 can be another source of electromagnetic energy, such as an electron beam. Regardless of the writing energy source, a light source is generally used for reading purposes.

The operation of the embodiment of FIG. 2 is the same as that of FIG. 1, and will not be described further.

FIG. 3 FIG. 3 uses the Kerr effect to write information to the storage film 10 rather than the Faraday effect illustrated with respect to the embodiment of FIGS. 5 shows an embodiment for reading information. In this example,
Beam 16 emerging from laser array 14 impinges on storage medium 10 after passing through a plane deflection element 18. Beam 16 is reflected from substrate 12, passes through analyzer 30 and strikes detector 32. Second
As in the case of the figure, an intensity control circuit 40 for changing the amplitude of the beam 16 is provided.

The operation of the device of FIG. 3 is the same as that of FIGS. 1 and 2. The only difference is that the beam 16 is reflected from the substrate 12 after passing through the membrane 10 rather than hitting the detector 32 after passing through the substrate 12. This type of readout utilizes the Kerr effect to provide information in exactly the same way as when the light beam 16 passes through the substrate 12.

FIG. 4 shows that the light beam generated by the laser 70 is
Shows the light modulator hitting the amorphous magnetic material 74 after reaching. There is an electromagnet 26 near the membrane. The direction of the magnetization in the sheet 74 can be changed by the magnetic field generated by the electromagnet 26. The degree of polarization of light passing through the amorphous sheet 74 is
It depends on the sign and the absolute value of the magnetization of the sheet 74. The intensity of the light passing through the analyzer 82 is determined by the polarization state of the light passing through the amorphous sheet. After passing through the amorphous sheet 74, the light beam strikes the analyzer 82 and is subsequently detected by the phototube 84.

Depending on the presence or absence of magnetic domains 78 where the light beam strikes amorphous sheet 74, the polarization of the light beam rotates in different directions. At some polarization rotation, the light beam is
Through the phototube 84 to generate a current in the resistor R. In the other case, the polarization rotation of the light beam is such that the beam does not pass through the analyzer 82 and no voltage is detected across the resistor R. Thus, a suitable sheet of amorphous magnetic material having magnetic domains therein provides a light intensity modulator.

In FIG. 4, it should be understood that rather than propagating through the amorphous sheet 74, light may be reflected therefrom. In both cases, the effect is the same, and the polarization of light is affected differently depending on the magnetization direction of the magnetic domain at the incident position of the light beam.

Recording Subsystem The amorphous magnetic material can be deposited as a recording medium on a substrate such as a semiconductor, an insulator, or a metal.
The substrate can be a tape or a disk. Further, the amorphous magnetic material can be prepared as magnetic particles mixed with an adhesive (such as a normal resin type adhesive) that can be used on any kind of substrate.

FIG. 5 shows a tape or disk recording medium 94 containing an amorphous magnetic film according to the present invention. Above it is a read / write head 96. Transducer 96 is used to record information in magnetic domains in tape or disk 94 and read information stored therein, in well-known fashion. For this purpose, an electrical signal is read from the recording medium 94 and sent to the sense amplifier 98 and from there to the utilization circuit 100. Usage circuit 100
May be any type of circuit used in ordinary computer technology.

Using an amorphous membrane according to FIG. 5 has a number of advantages. The disk or tape substrate may be a flexible substrate or a rigid substrate. Therefore, it can be used for any type of information processing system. In addition, the amorphous material is easy to adhere uniformly to any type of substrate, resulting in uniform magnetic properties everywhere.

The following non-limiting examples are provided to further illustrate the present invention.

By magnetron sputtering from U and Sb and optionally Co or Mn targets,
A USb film is deposited at 300K on a rotating glass substrate. 8
Starting from a reference pressure of × 10 ⁻⁵ mTorr, sputtering is performed at an Ar pressure of 3 mTorr and an Ar flow rate of 30 sccm. The film for Faraday measurement was 800 mm thick, and the film for measurement of resistivity, magnetism and Kerr rotation was 2000 mm thick. All samples were coated with 400 ° of SiO ₂ to prevent oxidation. The film thickness was measured with a profile meter, and the film composition was
Determined using Rutherford backscattering and inductively coupled plasma atomic emission spectroscopy. The amorphousness was confirmed by X-ray diffraction.

The magnetic measurement was performed using a superconducting quantum interference device (SQUID) magnetometer while applying a magnetic field H of 40 kOe at the maximum parallel and perpendicular to the film plane. Resistivity [rho and the Hall resistivity [rho _H, using the fan = der = Pauw method, was determined by applying a magnetic field perpendicular to the film plane in a magnetic field of 17KOe. From the values of ρ and ρ _H , Θ _H = ar
It was calculated hole angle using the ctan (ρ _{H /} ρ). In all U-Sb composition was measured, theta _H is a positive value. Faraday rotation _F and magneto-optical Kerr rotation _K were measured using an Oxford optical dewar in a magnetic field of up to 40 kOe with a magnetic field perpendicular to the film plane. In order to obtain sufficient light transmission for the measurement of the Faraday effect, the film thickness is less than 800 mm. With energy E in the range of 1.55 to 2.76 eV, H = ±
In 40 kOe, to measure the energy dependence of theta _F and theta _K,
Temperature and magnetic field dependence were measured at E = 2.25 eV (wavelength 500 nm). For all U-Sb composition was measured, the value of theta _F is positive, the value of theta _K was negative.

 Table 1 shows the results for the various alloys.

Magneto-optical data of the alloy at about 48:52 are shown in FIGS.

FIG. 6 shows the energy dependence of Faraday rotation at 10K. This data is obtained by averaging data obtained at +40 kOe and -40 kOe. Rotation at 1.8 eV is 2.2 × 10
Note that it exceeds ⁶ degrees / cm. FIG. 7 shows similar data obtained at 100K. The rotation is greater than 1.5 × 10 ⁶ degrees / cm for most of the investigated wavelength range. The Faraday loop from −40 kOe to +40 kOe at 80 K is shown in FIG. Technical saturation occurs at 5 kOe, but full saturation appears to be above 40 kOe. This type of high magnetic field susceptibility is characteristic of materials with large random anisotropy. An alloy having a higher U content has a higher magnetic susceptibility in a high magnetic field region. 9K in Fig. 9
The loop in shows a very large coercive force of 23 kOe. The residual rotation is about 81% of the value at 40 kOe. The 60:40 alloy shows a much smaller square loop at 10K. Meanwhile, 80K
The 40:60 alloy has a higher residual rotation (15%) than the 48:52 alloy (about 2%, see FIG. 8).

FIG. 10 shows the results at 1 kOe of an 800-μm thick film of U _0.51 Sb _0.49 .
Is a graph in which is plotted. This figure shows the applied magnetic field (F
Instead of cooling the sample in C), start with 0 (zero)
The difference observed when cooling the sample with a magnetic field and then applying a magnetic field (ZFC) to measure is shown. In the ZFC sample, M (T) increases monotonically with increasing temperature.
Hall resistivity ρ _H (T) shows the same temperature dependence as M (T). In Table 1 above, the values of the magnetization measured using a magnetic field parallel to the plane M are given. In the temperature dependence measurement of resistivity ρ (T) from 4K to 300K, ρ (T) is almost temperature independent, from 135μΩcm of U _0.8 Sb _0.2 to 5 of U _0.3 Sb _0.7
It can be seen that it changes monotonically up to 58 μΩcm.

Unique Faraday rotation Θ _F (degrees / cm), 10K ≦ T ≦ 200
Measured as a function of temperature, K, H = ± 40 kOe. To the 11a diagram showing a specific Faraday rotation Θ is converted into _F, a plot of temperature dependence of the average value of the difference in rotation in positive and in negative magnetic field. This figure shows basically the same behavior as that seen in magnetization. All systems except U _0.48 Sb _0.52 show a high temperature tail, which is generally thought to be due to fluctuations or short-range magnetic order. H = 40kOe,
T = the value of theta _F at 10K is, U _0.85 Sb _0.15 of 0.3 × 10 ⁶ ° / cm
From U _0.48 Sb _0.52 to 2.2 × 10 ⁶ degrees / cm. In FIG. 12, when H is between +40 kOe and -40 kOe,
Temperature 10K, 25K, 50K, a plot of theta _F as a function of magnetic field at 80K shown. As a result, a large coercive force H _c is obtained, the coercive force is consistent with the observed behavior at the other amorphous metallic like TbFe _2. For TbFe _2, large H _c is believed to be due to the presence of the single-ion anisotropy.

The Kerr rotation _{Θ K, 10K ≦ T ≦ 200K} , was measured as a function of temperature at H = ± 40 kOe. FIG. 11b shows a graph plotting the temperature dependence as the average of the difference in rotation in positive and negative magnetic fields. Temperature dependence of the five systems all at Θ _K is, M
(T) and _{Ｆ F} (T) show basically the same behavior as the behavior observed. H = 40 kOe, the value of theta _K at T = 10K is, U
_It can be seen that the range extends from -0.25 degrees of _0.15 Sb _0.85 to -3.2 degrees of U _0.51 Sb _0.49 .

The energy dependence of theta _F in various compositions are shown in Figure 13a the plot for the case the photon energy E is 1.77～2.76EV. _{Ｋ K} when E is 1.55 to 2.76 eV
13b is shown in FIG. 13b. In both cases, there is little evidence of dispersion and the spectral change with composition is significantly smaller. Furthermore, the fractional change as a function of temperature for both で も_{F and ＫK} is essentially zero.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor McGallare, Thomas, Roche, 620 Madison Court, Yorktown Heights, New York, USA (72) Inventor Plasket, Thomas, Stanley Holly, Kattonah, NY Hill Lane, R.F. 5 (56) References JP-A-61-121404 (JP, A) JP-A-63-136344 (JP, A)

Claims (3)

(57) [Claims] 1. An amorphous alloy exhibiting magneto-optical rotation comprising uranium and antimony in a component ratio of 60:40 to 40:60 and further containing 10 to 20 atomic% of Mn, Co or both. 2. A magneto-optical storage medium comprising an amorphous alloy containing uranium and antimony in a component ratio of 60:40 to 40:60, and further containing 10 to 20 atomic% of Mn, Co, or both. 3. A magneto-optical storage medium comprising an amorphous alloy containing uranium and antimony in a component ratio of 60:40 to 40:60 and further containing 10 to 20 atomic% of Mn, Co or both. Heating means for locally heating a selected area of the storage medium, and magnetic field generation for generating a magnetic field in the selected area to change a magnetic state of the storage medium in the selected area Means for changing the magnetic state of a plurality of selected areas of the storage medium, and optical means for directing a polarized light beam to the selected areas of the storage medium; Detecting means for detecting the degree of rotation of the polarization of the light beam rotated according to the magnetic state of the area, read means for detecting the magnetic state of the selected area of the storage medium, With That, magneto-optical storage system.