JPH0959022A - Production of manganese-based perovskite oxide thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject oxide thin film having extremely great magnetic resistance effect. SOLUTION: This thin film consisting of an Mn-based perovskite oxide of the formula AMnO3 (A is at least one metal selected from La, Pr, Ca and Sr) is obtained by coating a substrate with an organic solvent solution containing an alkoxide of the metal A and an Mn alkoxide or acetyl acetonate or a solution prepared by incorporating the above solution with water in such a proportion as to be <=1.5 based on the valence of the metal A followed by partial hydrolysis, and then by drying and baking the applied solution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a Mn-based perovskite oxide thin film having a giant magnetoresistive effect.

[0002]

2. Description of the Related Art The giant magnetoresistive effect means that electric resistance changes greatly when a magnetic field is applied, and it was discovered in a metallic artificial lattice Fe / Cr.

This is followed by Co / Cu and many (F
e, Co, Ni, their alloys) / (Cu, Ag, Au)
A giant magnetoresistive effect has been found in a noble metal such as or a transition metal such as Cr or Ru) artificial lattice.

At present, research on the mechanism of the giant magnetoresistive effect and its application are being actively conducted.

Regarding the application of the giant magnetoresistive effect, research on a giant magnetoresistive multilayer thin film utilizing a coercive force difference and magnetic anisotropy for the purpose of the soft magnetic giant magnetoresistive effect has been advanced.

A typical example is a spin valve giant magnetoresistor, which is expected to be applied to a magnetoresistive head for reading high-density magnetic recording.

Conventionally, the giant magnetoresistive effect has been observed in the metal system, but recently, the giant magnetoresistive effect was also found in the oxide system (Nature, vol. 373, No. 2,).
p. 407-409 (1995)).

It is believed that the discovered Mn-based perovskite oxide undergoes a structural phase transition upon application of a magnetic field, resulting in a large electrical resistance change.

The above oxide is produced by mixing oxides, carbonates, etc., calcining (solid phase reaction method), forming and firing a powder, which is then sintered, and further zone melted. .

[0010]

The bulk of Mn-based perovskite oxide is difficult to miniaturize and combine with other devices on the substrate, so that the application range of magnetic sensors utilizing the giant magnetoresistive effect is limited. narrow.

In order to expand the application range of the giant magnetoresistive effect of the Mn-based perovskite oxide, it is desired to manufacture a thin film capable of miniaturization and various patterning.

However, the conventional solid phase method can produce a bulk shape, but has a problem that a thin film cannot be produced or patterned.

Further, in the solid phase method, since the reaction temperature is high, the composition shifts due to the evaporation of a part of the components, and the purity lowers due to the inclusion of impurities from the furnace.

On the other hand, a vapor phase method such as sputtering or CVD is conceivable as a method for producing a thin film, but decompression and a vacuum container are required, and the reaction apparatus becomes complicated.

Further, in a multi-component system such as Mn-based perovskite which exhibits a giant magnetoresistive effect, it becomes difficult to control the composition.

The present invention was devised in order to solve the above-mentioned problems, and it is easy to control the composition and to carry out low-temperature synthesis.
It is an object of the present invention to provide a method for producing an n-based perovskite oxide thin film.

[0017]

The present invention has been made to achieve the above object. That is, the general formula AMn
Organic solvent solution of alkoxide of metal A and alkoxide of Mn of perovskite type oxide represented by O ₃ (where A is one or more kinds of metal selected from the group of La, Pr, Ca and Sr) or the above solution Then, a solution of partially hydrolyzed water with a ratio of 1.5 or less with respect to the valence of the metal is applied to the substrate, dried and baked to produce a Mn-based perovskite oxide thin film.

Alternatively, a solution of an alkoxide of metal A and an acetylacetonate of Mn in an organic solvent or a solution obtained by partially hydrolyzing water by adding water in a ratio of 1.5 or less with respect to the valence of the metal is used as a substrate. After coating, it is dried and baked to produce a Mn-based perovskite oxide thin film.

The alkoxy group of the metal alkoxide is not particularly limited, and examples thereof include methoxy group, ethoxy group, butoxy group, propoxy group, methoxyethoxy group,
An ethoxy ethoxy group or the like can be used.

Further, an alkoxide derivative in which a part of the alkoxy group is substituted with β-diketone, β-ketoester, alkanolamine, alkylalkanolamine, organic acid or the like can also be used.

The organic solvent for dissolving the metal alkoxide or acetylacetonate is not particularly limited as long as the metal alkoxide of the present system is soluble, but alcohols such as methanol, ethanol, butanol, propanol, methoxyethanol and ethoxyethanol, Ether, benzene, toluene, xylene and the like can be used.

The solution of the metal alkoxide or acetylacetonate can be directly applied to the substrate, but a solution obtained by partially hydrolyzing water may be applied to the substrate. At that time, the amount of water added is preferably 1.5 or less with respect to the valence of the metal in the system. If it exceeds 1.5, precipitates are generated in the solution and a homogeneous thin film cannot be produced.

The coating on the substrate is performed by a spray coating method, a dip coating method, a spin coating method or the like.

[0024]

EXAMPLES The method for producing a Mn-based perovskite oxide thin film according to the present invention and the Mn-based perovskite oxide thin film obtained thereby will be specifically described by the following examples. However, the present invention is not limited to only these examples.

[0025]

Example 1 Metal Sr was added to excess dry ethanol,
The mixture was heated and refluxed for reaction to prepare an ethanol solution of Sr ethoxide.

La isopropoxide and M were added to the solution.
n ethoxide was replaced with La _1-x Sr _x MnO ₃ (x = 0.17)
And ethoxyethanol in the same amount as ethanol, and the mixture was heated and refluxed.

This solution was applied to a Si substrate by a spin coater and dried at 110 ° C. After repeating the above-mentioned coating and drying operations 5 times, it is baked at 800 ° C. for 2 hours to obtain La _1-x Sr _x.
A MnO ₃ perovskite thin film was prepared.

FIG. 1 shows an X-ray diffraction pattern of the produced thin film.
From the diffraction peak, it can be seen that the phase is La _1-x Sr _x MnO ₃ perovskite phase. FIG. 2 shows the measurement results of the magnetic resistance of this thin film. The resistance dropped sharply when a magnetic field was applied, showing a giant magnetoresistive effect.

[0029]

Example 2 Add metal Ca to excess dry ethanol,
The mixture was heated and refluxed for reaction to prepare an ethanol solution of Sr ethoxide. Pr isopropoxide and Mn ethoxide were added to the above solution in the form of Pr _1-x Ca _x MnO ₃ (x = 0.
In addition to the ratio of 3), ethoxyethanol in an amount equal to ethanol and ethyl acetoacetate in an equimolar amount to all metals were added, and the mixture was heated and refluxed.

Water was added to the above solution in an amount 1 mole times the valence of all metals, and the mixture was further heated and refluxed. The obtained solution was applied to a Si substrate with a spin coater and dried at 110 ° C. After repeating the coating and drying operation 5 times, 800 ° C
It was baked for 2 hours to prepare a Pr _1-x Ca _x MnO ₃ perovskite thin film.

FIG. 3 shows an X-ray diffraction pattern of the produced thin film.
It can be seen from the diffraction peak that it is a Pr _1-x Ca _x MnO ₃ perovskite phase. FIG. 4 shows the measurement results of the magnetic resistance of this thin film. The resistance dropped sharply when a magnetic field was applied, showing a giant magnetoresistive effect.

[0032]

Since the present invention is constructed as described above, it has the following effects.

In the method for producing a Mn-based perovskite oxide thin film of the present invention, since the thin film is produced from the solution in which the constituent metals are uniformly mixed, it can be produced at a lower temperature than the conventional solid phase method. .

This saves energy consumption of the firing apparatus and the like and prevents impurities from entering at high temperatures. Further, according to this method, a thin film can be easily produced, so that the magnetic sensor can be miniaturized and can be directly produced on a circuit board.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the produced thin film.

FIG. 2 is a graph showing a resistance change of a manufactured thin film due to an applied magnetic field.

FIG. 3 is an X-ray diffraction diagram of the produced thin film.

FIG. 4 is a graph showing a resistance change of the manufactured thin film due to an applied magnetic field.

Claims (2)

[Claims] 1. A general formula AMnO ₃ (where A is La, P
In the method for producing a thin film of a perovskite-type oxide represented by one or more metals selected from the group consisting of r, Ca, and Sr), an organic solvent solution of an alkoxide of metal A and an alkoxide of Mn, or a metal in the solution. A method for producing a Mn-based perovskite oxide thin film, which comprises applying a partially hydrolyzed solution to the substrate by adding water in a ratio of 1.5 or less to the valence, and then drying and firing the solution. 2. A general formula AMnO ₃ (where A is La, P
In the method for producing a thin film of a perovskite-type oxide represented by (1 or more metals selected from the group consisting of r, Ca and Sr), an organic solvent solution of the alkoxide of metal A and acetylacetonate of Mn or the above solution. A method for producing a Mn-based perovskite oxide thin film, characterized in that water is added to the substrate at a ratio of 1.5 or less with respect to the valence of the metal, and the partially hydrolyzed solution is applied to the substrate, followed by drying and firing. .