DE2558937B2 - MAGNETO-OPTICAL THIN FILM MEMORY AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Description

where χ + y + ζ = I, 0.15 S χ ^ 0.70, 0.10 £ y g 0.55, 0.11 g ζ g 0.55 and 0 </ <I.

2. Thin film according to claim I, characterized in that that an element selected from the group is added to the composition which consists of Ti, V, Cr, Fe, Nb, Te, Y, Ce, Nd, Gd and Dy.

3. Thin film according to claim 1, characterized in that an element is added to the composition is added, which is selected from the following group: Co, Pd and Rh.

4. Thin film according to claim 2, characterized in that the amount of one element which is selected from the group Ti, V, Cr, Fe and Nb is equal to 0.035 mol per mol named composition.

5. Thin film according to claim 2, characterized in that the amount of one element of the Groups Ti, V, Cr, Fe and Nb are equal to 0.07 moles per mole of said composition.

6. Thin film according to claim 2, characterized in that the amount of one element of the Group corresponding to Y, Ce, Nd. Gd and Dy are equal to 0.075 moles per mole of said composition.

7. Thin film according to claim 2, characterized in that the amount of one element of the The group corresponding to Y, Ce, Nd, Gd and Dy is equal to 0.15 mol per mol of said composition.

8. Thin film according to claim 2, characterized in that the amount of Te is equal to 0.03 mol per mole of said composition.

9. Thin film according to claim 2, characterized in that the amount of Te is equal to 0.06 mol per mole of said composition.

10. Thin film according to claim 3, characterized in that that the amount of Co is equal to 0.07 mol per mol of said composition.

11. Thin film according to claim 3, characterized in that that the amount of Pd is equal to 0.14 mol per mole of said composition.

12. Thin film according to claim 3, characterized in that that the amount of Rh is equal to 0.07 moles per mole of said composition.

13. Thin film according to claim 1, characterized in that 0.20 g χ g 0.55, 0.15 g y ^ 0.45 and 0.13 ^ ζ g 0.43.

14. A method for producing a magneto-optical thin film according to claim 1, characterized in that on eir.om substrate which is selected from a group corresponding to glass, fused quartz, mica, SiO-coated metal and SiO ₂ -coated metal, in an arbitrary Order the elements Mn, Cu, Ni and Bi are deposited and that this arrangement / to achieve diffusion is then annealed or tempered.

15. Verfuhren according to claim 14, characterized in that that the four elements Mn, Cu, Ni and Bi are deposited on the substrate simultaneously will,

The invention! relates to a magneto-optic thin film for memory devices.
ίο With the conventional magneto-optical thin films for memory, a Mn-Bi-FiIm is of great importance for an effective readout. The film takes on a storage function in the following way: First, a laser beam is directed onto a microzone of the film, which is magnetized beforehand in a direction perpendicular to the surface of the film. The micro-zone receiving the laser beam absorbs the light energy of the beam, thereby increasing the temperature of the micro-zone.

When the temperature exceeds a Curie point, the microzone is demagnetized. Then the Laser beam irradiation stopped. This then keeps the temperature of the microzone below the Curie point lowered, resulting in magnetization

leads in a direction opposite to the

other zones of the film. This process becomes writing using the Curie point method called.

The quality of a magneto-optical thin film

jo for memory is from the standpoint of write performance and evaluated from the standpoint of the readout signal-to-noise ratio. In the case of the Curie point method, the The amount of writing power proportional to the difference between a room temperature and a Curie point of the film. As a result, the writing performance of a magneto-optical thin film with low Curie point is low. A small writing performance is an absolute requirement or one Requirement for a magneto-optic thin film. On the other hand, a magneto-optic figure of merit 2F / a, where "F" is a Faraday rotation angle for a unit thickness of the film and "" "represent a light absorption coefficient, a parameter for the evaluation of a read-out signal-to-noise ratio

of the film. A large value of 2 F / a is also absolutely necessary for a magneto-optic thin film. In J. Appl. Phys., Vol. 43, S. 2875 (1972) describes a magneto-optical thin film of the Mn-Bi-Ti system. Next is in the Reference "Solid State Communication", Vol. 14,

P. 33 (1974) describes a system of Mn ₅ Ni ₂ Bi ₄ and Mn ₃ Cu ₄ Bi ₄ . These substances have relatively low Curie points.

It is an object of the present invention to provide a magneto-optic thin film which can function as a preferred storage medium. The magneto-optical thin film should have a low Curie point.
The present invention is also intended to provide a magneto-optical thin film with good magneto-optical properties. The magneto-optical thin film should have a good magnetic hysteresis characteristic. In addition, the magneto-optical thin film should be free from phase transformation and should also be chemically stable. The present invention also relates to a method for producing a magneto-optical thin film with good reproducibility.

In order to solve the problem mentioned, the present one creates Invention of a magneto-optical thin film, its composition by the following formula lefinierl is:

Mn _x (Cu ₁ _ _y , Ni _y ,) yBi, S

Here χ + y + τ = l, 0, l5gx | 0.70, 3.10 g y g 0.55, 0.11 gzg 0.55 and 0 </ <] The composition thus defined results in the thin film product having a single phase _[0 of cubic structure. A more preferred composition can be obtained by changing the conditions of the formula given above to O, IO Sx | 0.55, 0.15 g y g 0.45 and 0.13 g ζ 0.43, the other conditions then being retained unchanged . An addition of Ti, V, Cr, Fe, Nb, Te, Y, Ce, Nd, Gd or Dy to the above-mentioned composition of the four-element system results in the film product having an increased right angle ratio Mr / Ms of the magnetic hysteresis loop, where » Mr « and» Ms «each represent a residual magnetization and a saturation magnetization and a magnetization value, respectively. Similarly, addition of Co, Pd, or Rh to the four element system can result in the film product having a lowered Curie point.

In the following the invention will be explained using an exemplary embodiment with reference to the drawings explained in more detail. It shows

Fig. I of the magnetic hysteresis loops ₁₀ _ magneto-optical thin film according to the present invention having a composition of

^M »0.3

O .34

35

which is grown on different substances,

F i g. Fig. 2 is a graph showing the relationship between temperatures and the Faraday rotation angles of the thin film of Fig. 1,

F i g. 3 is a graph showing the Faraday rotation angles of the thin film of FIG. 1 opposite Wavelengths of laser beams,

F i g. 4 is a graph of Kerr rotation angles of the film of F i g. 1 versus wavelengths of laser beams and

Fig. 5 shows a range of compositions of a magneto-optic thin film according to the present invention Invention.

A magneto-optical thin film according to the present invention can be obtained by using a vacuum deposition method or a sputtering method using a substrate made of glass, fused quartz, mica or an aluminum plate coated with silicon monoxide or silicon dioxide. It is assumed that a thin film of the Mn-Cu-Ni-Bi system was formed by a vacuum deposition method on a micro-glass plate measuring 2 cm × 2 cm × 0.5 mm, as described by Corning Glass Works in is available in the USA. In this case, the size of these elements is determined first. After a Bi layer has been deposited on the glass plate, Mn, Cu and Ni are simultaneously nictleroeschlased from a single source or, alternatively, from separate sources. to form three to five layers of these metals on the Bi layer, whereupon a protective film of SiO several thousand Å thick is applied to these layers. Finally, the resulting mass is ^{calcined at 300 to 400 °} C., specifically for several hours, in order to bring about diffusion. The layer made from Mn, Cu, Ni and Bi can be optimally adjusted so that a thickness of over 200 Å is formed. The protective film, which is not necessarily required for the formation of a magneto-optic thin film, serves to improve the optical properties of the film. For example, the protective film serves to prevent light from being reflected. It is sufficient to create a vacuum in an amount of 1 x 10 ^-6 Torr or less at the time of precipitation and annealing.

In the case of a sputtering method such as a direct current sputtering method, atoms of elements constituting a magneto-optic thin film are emitted from targets at a vacuum of 1.3 · 10 ~ 'Torr to thereby form a desired film thickness on a fused quartz substrate which has previously been sufficiently cooled with liquefied nitrogen, followed by annealing under vacuum corresponding to 1 × 10 " ^fi Torr, in order to thereby achieve ferro-magnetization.

The order of precipitation of the four basic elements Mn, Cu, Ni, Bi with or without an addition of Ti, V, Cr, Fe, Nb, Te, Y, Ce, Nd, Gd, Dy, Co, Pd or Rh does not have any significant influence the thin film product. Whatever the order of precipitation, the thin film product possesses essentially the same properties. This applies to both vacuum deposition processes as well as calhodic atomization.

Table 1 shows the Curie temperatures T ₁ . ("C) and the magneto-optical figure of merit 2F / a of thin-film samples 1 to 29, each 400 Å thick and forming the Mn-Cu-Ni-Bi system, which is on micro-glass plates from Corning Glass Works in USA A laser beam having a wavelength of 6328 Å was used to determine the values of 2F / <* It can be seen that Samples 3,9,20,21,26, 27,28 and 29 are compositions outside the range specified by the present invention, in these samples, crystalline phases other than the cubic structure coexisting with the cubic system were found, and the values of 2F / a of these samples were also small.

The compositions of all of the remaining samples are within the range of the present invention. It was also found that these remaining samples are a single phase of a cubic Structure have equally large values of 2F / <x and preferred values of the Curie points.

In the following, the production method of sample 16 of Table 1 will be described as an example fc'gcndc has the following composition:

Mn ". _JS (Cu ".K

) ,,, j. ·, Bi ₁ , _u

example

Five substrates each from five mi '.' Crialarten what makes up a total of 25 substrates, were

Depressed strat holder of a vacuum deposition device. Specifically, the substrate used was made of glass, fused quartz, mica, an aluminum plate coated with SiO and an aluminum plate coated _{with SiO 2.} and s was about 1 μm thick. Each substrate was 20 mm × 20 mm × 0.1 to 1 mm in size.

A conical basket heater was located in the precipitation device for the purpose of precipitation with a tungsten wire, a fireplace heater and two ι ο Electron guns. One of the two electron guns was built according to the one-hearth type and the other three-stove type. It was thus found that the bodice apparatus has six kinds of materials could precipitate on the spot.

During the precipitation and annealing steps, the substrate holder supporting the base plate was rotated at a speed of 2 to 10 U / min, and the precipitate device was evacuated to a vacuum of less than 1 ■ 10 ^-6 Torr.

Bi was first deposited on the substrate using the conical basket heater to form a film 240 Å thick with a film growth rate of 2 to 5 Å / sec. Subsequently, Mn, Cu and Ni were deposited successively on the Bi layer. The one-hearth electron gun door deposition of Mn was used to form a film 82 Å thick, the film growth rate being 0.2-0.5 Å / sec. On the other hand, Cu and Ni were deposited using the three-hearth electron gun to form a Cu layer 63 Å thick at a rate of 0.2 to 0.5 Å / sec and a Ni layer 14 Å thick with a ₃ _s to generate a speed of 0.2 to 0.5 Å / s. Finally, an SiO layer of about 3000 Å thick was formed on the Ni layer at a rate of about 3 Å / s using the chimney heater.

The thus coated substrate was then heated to 400 ⁰ C at a rate of about 3 ° C / min to an annealing for about 8h. to be carried out, followed by cooling at a rate of about 4 ° C / min.

Then, the thickness of each deposited layer was measured by a quartz crystal thickness monitor manufactured by Solan Inc.

The remaining samples were prepared in essentially the same manner as Sample 16.

Table 2 shows the magnetic hysteresis characteristics, namely the coercive force H _c and the perpendicular ratio MrjMs of the magneto-opus thin films (samples 30 to 73), which were prepared by adding another element "M", 5s which * us of the group of Ti, V, Cr, Fe, Nb, Te, Y, Ce, Nd, Gd and Dy was selected based on the four element system of Mn-Cu-Ni-Bi. All Dünnfihne shown in Table 2, each having a thickness of 400 ⁰ C, has been formed on glass substrates (Mflcro-GlaspBttchen Corning Glass Works, USA). Table 2 also shows the magnetic hysteresis characteristics of Samples 12, 13, 14 and 15, which are illustrated in Table 1 as examples of the thin films without the addition of "M" for comparison. Samples 30 to 73 were prepared in essentially the same manner as Samples 1 to 29, except that the order of precipitation of Mn, Cu, Ni, Bi and the suffix "M" was arbitrarily changed.

Table 2 shows that the magnetic hysteresis characteristics of the thin films made of the five-element system of Mn-Cu-Ni-Bi-M are better than those of the four-element system corresponding to Mn-Cu-Ni-Bi. For example, sample 35 was prepared by adding 0.07 moles of vanadium to one mole of sample 13 and resulted in 2.0 KOe of coercive force H _c and 1.0 of perpendicular ratio Mr / Ms in contrast to sample 13 with 1.2 KOe of Hc and 0.7 of MrjMs.

Table 3 shows the Curie temperatures T _c of samples 74, 75 and 76, which were prepared by adding Co, Pd or Rh to the four-element system corresponding to Mn-Cu-Ni-Bi. Control cases are also shown in which the additive was not used. The samples listed in Table 3 were prepared in essentially the same way as the samples according to Table 2. It can be seen that Co, Pd and Rh are very effective in lowering the Curie temperature of the magneto-optical thin film.

Tabel

sample
No. MniCu,. ,, N 0.14 VO ₁ Bi = ζ Curic
tonpe- Magneto-
optical X 0.12 .v ' rature Giiiezifler 0.40 (Degree) 0.30 0.22 ( ⁰ C) (2FM 1 0.64 0.20 0.40 0.27 120 0.43 2 0.61 0.20 0.44 0.10 122 0.45 3 0.50 0.20 0.40 0.20 126 0.20 4th 0.50 0.20 0.40 0.30 147 0.87 5 0.50 0.08 0.20 0.30 148 0.83 6th 0.50 0.41 0.44 0.30 122 0.68 7th 0.50 0.20 0.60 0.30 116 0.61 8th 0.50 0.30 0.80 0.45 107 0.54 9 0.47 0.30 0.40 0.18 135 0.15 10 0.41 0.30 0.44 0.40 137 0.57 Il 0.40 0.30 0.40 0.32 130 0.60 12th 0.38 0.33 0.11 0.32 186 1.10 13th 0.38 033 0.14 0.32 182 1.06 14th 0.38 033 0.21 0.32 159 0.94 15th 0.38 033 0.40 034 135 0.71 16 0.33 0.07 0.20 034 187 !, 13 17th 033 0.07 0.44 034 137 0.79 18th 033 037 0.60 034 125 0.65 19th 033 0.25 0.80 042 118 0.69 20th 031 0.25 03) G, 62 185 03) 21 031 0.25 0.40 O37 165 0.15 22nd 035 0.60 0.44 0 ^ 0 167 0.80 23 0.25 0.60 03) 0.50 182 1.07 24 0.25 033 0.80 030 122 0.80 25th (U5 033 035 03) 100 0.80 26th 03) 0.10 03) 182 033 27 03) 0.40 036 142 0.25 28 0.11 0.10 036 * 185 0.22 29 0.11 0.40 128 0.08

Tabel

Sample no.

additive

no

Ti

Nb

Te

Ce

Nd

Mn ₀ .., "(Cu _n . _H9 Ni" _ "\, ,,, Bi ₀ Mn _0-38 (Cu _0-86 Ni _0-14 ) O ₁₃₀ Bi _0-32 Mn ₀₃₈ (Cu _{0 7q} Ni _{( 12I} \ ,, ₀ Bi ₍₎ ., ₂ Mn _0- J ₁₈ (Cu _0-60 Ni _n-40 ) I _1-30 Bi ₀₁₃₂ Mn ₀₃₈ (Cu ₀₈₆ Ni ₁₁₁₄ K) ₁ J ₀ Bi _0-32 : Ti ₀₀ J ₅ Mn ₀ j _B (Cu _{0 Kfl} Ni ₀ , 4I ₀ J ₀ Bi ₀ , ₂ : Ti _0-07 Mn ₀ J ₈ (Cu _0-60 Ni ₀ 4 ") b ,,, Bi ,, j ₂ : Ti _0-35 Mn ₀ J ₈ (Cu ₀ (, (, Ni ₀₄₀ Iu J ₀ Bi ₀ j2: Ti _0-07

Mn ₀ J ₈ (Cu _0-86 Ni _{0 14} \, j ₀ Bi _0. , ₂ : V ₀₀₃₅ Mn ₀ J ₈ (Cu _08n Ni ₀₁₄ H, J ₀ Bi ₀ j ₂ : V _0-07 Mn _0-38 (Cu _0-60 Ni _0-40 Ib _-30 Bi (J _-32 : V _0-035 Mn ₀ J ₈ (Cu _{0 60} Ni ₀₄₀ ) b J ₀ Bi _0- J ₂ : V _0-07

Mn ₁ , J ₈ (Cu _{0 S6} Ni _0-14 ) t) .3 ₀ Bi _O- j ₂ : Cr ₀₀ J ₅

M ^ _1- J ₈ (Cu _0- H ₆ Ni ₀₁₄ Ib ₁ JoBi ₀ .32: Cr _0-07 Mn ₀ J ₈ (Cu _{0 60} Ni ₀₄₀ ) bJ ₀ Bi ₀ j ₂ : Cr _0-035 Mn ₀ J ₈ (Cu _{0 60} 4 ₀ ,, Ni). bJ ₀ Bi _{0 32:} Cr _0-07

Mn ₀ J ₈ (Cu ₀₁ H ₆ Ni _0-14 I) _- J ₀ Bi _0- J ₂ : Fe _0-035 Mn ₀ J ₈ (Cu _0-86 Ni ₀ ult, J ₀ Bi ₀ j ,: Fe ₀ Mn ₀ J ₈ (Cu ₀ ,, (, Ni ₁₁₄₀ Ib.J ₀ Bi _{0 32} ^: Fe _{0 O35} Mn ₀ J ₈ (Cu ₀ (, (, Ni ₀₄₀ Ib.3I ₃ Bi ₀ j ₂ : Fe ₀

Mn ₀ J ₈ (Cu _0-86 Ni _0ι14 ν _{) ι30} Βί ₀₁₃₂ : Nb _OiO35 Mn ₀ J ₈ (Cu _0-86 Ni _{0 14} ) b, j ₀ Bi ₀ j ₂ : Nb _0-07 Mn ₀ J ₈ ( Cu _{0 60} Ni (, 4 (, I _0-30 Bi _{0 32} : Nb _{0 03;} Mn ₀₃₈ (Cu ₀₆₀ Ni ₀ ^ ₀ Jb _-30 Bi _0-32 : Nb _0-07

Mn ₀ .j ₈ (Cu ₀ , ₇ 9Ni _{0. 21} ) b.3oBio.32 ^; Te ₀ Mn _0- J ₈ (Cu _0-79 Ni ₀₂₁ ) O ₁ J ₀ Bi ₀₃₂ : Te ₀ Mn ₀ J ₈ (Cu ₀₆₀ Ni ₀₁₄₀ Ib ₁₃ OBi ₀₁₃₂ : Te ₀ Mn _0-38 (Cu _{0 60} Νί _{0 -4} ο ^ _-3 οΒί _0- 32 ^: Te ₀ Mn _0-38 (Cu _0-89 Ni _0- H) _0-30 Bi ₀₃₂ : Y _0-075 Mn _0i38 (Cuo _-89 Nio _-n J _0-30 Bi _0-32 : Y _0-15 Mn ₀ .38 (Cu _{0 60} Ni ₀ .4o) or.3oB'o.32 ^: Y0.075 Mn ₀ .3 ₈ (Cu _{0. 60} Ni _0- 4 ₀ ) b .3oBi _{0. 32} : Y _o , ₁₅

_{0 -S9} NI _{0 iU} J ₀ , ₃₀ Bi ₀ . ₃₂ : Ce _{0 07 s} Jb.soBio.aa ^: Ce _0-15 ) Q _-30 Bi _0-32 : Ce ₀ Mn _0i38 (Cu ₀₆₀ Ni _0i40 ) b, ₃ oBio _i32 : Ce _0il5

Mn ₀ J ₈ (Cu ₀₁₈₉ Ni ₀₁ H) _0-3 OBi ₀₁₃₂ : Nd _Oi07 5 Mn _OJg (Cu _0ig9 Ni _0ill ) o, 3oBio, 32: Nd _o , i _S ^^ οΒϊο ^ Σ ^: Ndo.075

: Od

Coercive force right angle ratio H ₁ (K (X-) , Mc · Af x 0.7 1.2 0.7 1.2 0.65 1.1 0.6 1.0 1.0 1.5 1.0 1.9 0.95 1.3 1.0 1.4 1.0 1.5 1.0 2.0 1.0 1.3 1.0 1.5 1.0 1.3 1.0 1.6 1.0 1.2 1.0 1.4 0.95 1.2 0.95 1.6 0.90 1.1 0.90 1.3 1.0 1.5 1.0 1.9 0.95 1.3 1.0 1.4 1.0 2.0 1.0 2.0 0.95 1.5 1.0 1.6 0.95 1.4 0.95 1.8 0.90 1.3 0.95 1.5 0.90 1.3 0.90 1.8 0.90 1.1 0.90 1.2 1.0 1.8 1.0 2.3 1.5 * T ₁ O 0.95 1.4 0.95 1.9 0.90 1.3 0.90 1.5

70S B31 / 3O4

additive 25 58 9 Film composition 937 ^ : Dy _0, 075 10 Right angle
ratio 7th : Dy _0-15 Mr / Ms continuation Dy Mn _0- J ₈ (Cu _0-89 Ni ₀ H) ₁₁ J ₀ Bi _0- J ₂ ^: Dy ₀ , 0 ₇₅ Coercive force
Wc (KOe) 1.0 Sample no. Mn ₀ .J ₈ (Cu ₀₈₉ Ni ₀₁₁ Ib J ₀ Bi _n ., J ^{: D} yo.i5 1.0 Mn ₀₁ J ₈ (Cu ₀₁₁₁₀ Ni ₀₄ Oi ₁ J _n Bi ₀₁ J ₂ 1.8 1.0 70 Mn ₀ J ₈ (Cu _{0 60} Ni ₀₄₀ ) b, j ₀ Bi ₀ j ₂ 2.4 1.0 71 1.6 72 additive Film composition 1.8 Curic 73 temperature
Το (Τ) Table 3 -Co ₀₀₇ curie without addition Sample no. · ■ Pd ₀ .μ temperature iKonlrollfalle) Co Mn _o , j ₈ (Cu ₀₈₆ Ni _ol4 ) b, j ₀ Bi _o , j ₂ ^{: R} ho.o7 187 Pd Mn ₀ , J ₈ (Cu _{0 i7S} N i _{0 -25} ) b .23 Bi ₀ , j ₉ ("C) 190 Rh Mn _0-35 (Cu ₀ , S ₉ Ni ₀₁₁₁ Ib _-28 Bi ₀₁ J ₈ 165 200 74 120 75 140 76

A moisture resistance test was then carried out on a magneto-optic according to the invention Thin film carried out. The thin film was exposed to a relative humidity of 50% at 50 ° C for 24 hours, whereupon the film was subjected to microscopic examination. There were at the Film area no changes noted. Another test was carried out at a relative humidity of 90% \ s carried out at 50 ° C for a corresponding period of 24 hours, with no change in the film surface area either was paid for.

The figures will now be discussed in detail. Fig. I shows magnetic hysteresis loops. | O of sample 16 shown in Table I and having the following composition:

Mn _o ", j (Cu _o , _HO Ni _n , a") _(UA Bi ", _iU

In view of the fact that the magnetization is proportional to the Faruday rotation angles Fi, where "F" denotes a Furuduy rotation angle RIr a unit thickness of the film and "(" a thickness (4 (X) λ) of the film, The values of Ft thus determined by the use of a laser beam having a wavelength of 6328 Λ were plotted on the Ordlnuto. The loops (a) and (b) in Fig. I show that the thin film on glass substrates, respectively the Rechiwinkllgkelts- "relationship MrIMs iur were formed and molten Quurz sub-μ struton. the loop (a) Mr don case of Olassubstrat" is kMner than 1.0, while dor value for the loop (b) in the case of fused silica is essentially equal to 1.0.Bios shows that the present invention creates the possibility that the value of MrIMs, which is an important characteristic of a magneto-optical recording film, reaches the value of 1.0, due to appropriate selection of the S substrate. ^

Fig. 2 shows the relationship between the temperatures and the magnetization of the DUnn film, the In Fig. I is used (sample 16) in plots of Faraday rotation angles Ff determined by using a laser beam having a wavelength of 6328 Å. It can be seen that the Curie point of the film was 187 ° C, which is about half that of a thin film. which consists of the intermediate menu system Mn-Hi. •

In the case of the FIG. 2 or the sample shown, the disappearance of the spontaneous magnetization due to the temperature increase is caused by secondary magnetic transition. It thus follows that an abrupt disappearance of the spontaneous magnetization, which is brought about by a primary crystal transition or crystal transition from the low-temperature phase to the low-temperature phase and which can be observed in a film of the Mn-Bi system, in the subject of the l · 'i G. - cannot be found.

Fig. 3 shows the Faraday roll angles F for the unit thickness of the film relative to the wavelengths of laser beams used to determine F. The test was at the high 16 (Exactly as for Fig. I) under a residual magnetization condition carried out.

F i g. 4 shows the relationship between the Kcrr rotation angle H _k and the wavelengths of laser beams used for the determination. The experiment was carried out on the sample. 16 under an initial state of notification as in the subject of FIG. 3, and the values of f) _{k were} measured from the oil substrate side of the sample. It was found that the maximum of "" was reached in the clegend of 5 (XK) A of the wavelengths.

Flg. Finally, FIG. 5 shows an angular coordinate corresponding to the compositions of a magneto-optical thin film of the Vicr element system according to Mn-Cu-Ni-B1. The ones outside of the dashed ones Zone-filling composition does not lead to an individual phase of the crystal system. The composition, for example, a predominant amount

of Bi, namely the uppermost zone of the angular coordinate, leads to a mixed phase of an angular and a cubic phase, the angular phase being represented by the excessively high content of Bi. This mixed phase mentioned is also indicated around the zone of Mn ₀₅ Bi _{0 5} , ie around the center of the line connecting the Mn-100% point and the Bi-100% point (MnBi is responsible for the problem). On the other hand, the composition of the zone along the line connecting the Bi-100% point and the Cu, _ ,,, Nij, -IOO% -point represents such a crystal phase, not cubic phase, and results in a Diffraction line of 2Θ - 17.5 "when subjected to X-ray diffraction using Cu-Kft rays and where" β "represents a" black angle ". Further, the composition of the zone near the Mn -100% -point a phase of K-) = 31.2 "(not cubic phase) observed. If the compositions fall within the dashed region of the angle coordinate, then the thin film contains a single phase of the cubic system, has a Curie point! from 100 to 200 ° C, has satisfactory magneto-optical properties and magnetic hysteresis characteristics and is extremely stable against moisture. The compositions falling within the dashed zone are defined by the formula:

Mn _x (Cu ₁ _ _y , Nv), Bi _z

where χ + y + ζ = \, 0.15 g χ ^ 0.70, 0.10 ί) ΐί 0.55, 0.11 ίζί 0.55 and 0 </ <1.

For this purpose 4 HhUt drawings

Claims (1)

Patent claims: 1. Magneto-optical thin film for storage devices, characterized, that the film has a composition according to the following formula: Mn _- (Cu ₁ - ,,, Nv) ₁₁ Bi ₂