JP2003252618A - Magnetic nanoparticle, method for producing the same, and magnetic nanoparticle thin film - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide magnetic nanoparticles having further improved functions as a magnetic recording material. SOLUTION: MX _p · nH ₂ O (M: transition metal or rare earth metal, X: all halogen elements, p and n: 0)
And a solution containing Na ₂ SiO _3.
Amorphous SiO ₂ + M _i O _j (i, j is 1 to 9) obtained by calcining a precipitate formed by uniformly mixing a solution containing mH ₂ O (all positive real numbers including m: 0). Integers), each M _i O _j
The present invention is characterized in that the nanoparticles are held in a state separated by an amorphous SiO ₂ network film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic nanoparticle, a method for producing the same, and a magnetic nanoparticle thin film capable of realizing ultrahigh density recording as an ultrahigh density recording medium of an ultrahigh density magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art Nanometer-scale fine particles bring about new and unique physical properties that have never been seen and can be expected to have high performance as a functional material. Therefore, various substances have been sought. For example, in recent years, with the development of an advanced information society, there has been a demand for high-density recording of information, and ultra-high-density magnetic recording using fine particles of ferromagnetic iron oxide has been developed. However, the particle size of the ferromagnetic fine particles for magnetic recording was larger than 10 nm, and it was impossible to achieve ultra-high density at the TB (terabyte) level as magnetic recording. Fine particles in the magnetic recording tape obtained by the conventional manufacturing method, for example, CoCrTa fine particles, have a diameter of about 30 nm. In view of this point, the present inventors have conducted various studies so far and established a method for producing magnetic nanoparticles having a particle diameter of 10 nm or less, which enables ultra-high density at the TB level for magnetic recording. (See JP 2001-261334 A). This method includes a solution containing MX _p · nH ₂ O (M: transition metal or rare earth metal, X: all halogen elements, all positive real numbers including p and n: 0), and Na ₂
A solution containing SiO ₃ · mH ₂ O (all positive real numbers including m: 0) was wet-mixed and allowed to stand to produce a precipitate, which was washed, dried and then calcined. The magnetic nanoparticles are obtained as amorphous SiO ₂ + M _i O _j oxide (i and j are integers of 1 to 9).

[0003]

Since the above-mentioned method for producing magnetic nanoparticles is unique and simple, and is economical in mass production, it is expected to be put into practical use at an early stage. This is where However, considering the speed of performance improvement in the industry related to magnetic recording, further improvement in the function of magnetic nanoparticles is required. For that purpose, it is necessary to optimize the production conditions and establish a method of separating and holding magnetic nanoparticles having a high coercive force and remanent magnetization at room temperature without aggregating them.

[0004]

SUMMARY OF THE INVENTION The present invention is a magnetic recording material.
Magnetic nano-particles with improved functions
It is intended to be provided, and in view of such points
The magnetic nano-particles of the present invention made according to claim 1.
And MX_p・ NH_TwoO (M: transition metal or rare earth gold
Genus, X: all halogen elements, all including p and n: 0
Positive real number) and Na_TwoSiO_Three・ MH_TwoO
Uniformly mix the solution containing (all positive real numbers including m: 0)
Amorph obtained by firing the precipitate generated by
As SiO _Two+ M_iO_j(I and j are integers from 1 to 9)
Magnetic nano-particles_iO_jNano particles
Amorphous SiO_TwoSeparated by reticulated membrane
It is characterized in that it is held in a state. In addition, claim 2
The magnetic nanoparticle according to claim 1 is the magnetic nanoparticle according to claim 1.
In the child, M_iO_jFe nanoparticles_TwoO_ThreeNano particles
Characterized by being a child. Further, the magnetism according to claim 3.
The nanoparticles are the magnetic nanoparticles according to claim 1.
M_iO_jFe Co-doped with nanoparticles_Two
O_ThreeIt is characterized by being nanoparticles. Also, the claims
The magnetic nanoparticle according to claim 4 is the magnetic nanoparticle according to claim 2 or 3.
In nanoparticles, Fe_TwoO_ThreeNano particles are γ-Fe
_TwoO_ThreeAnd α-Fe_TwoO_ThreeCoexisting with nano particles
Is characterized by. Further, the magnetic nanoparticle according to claim 5.
Is M in the magnetic nanoparticles according to claim 1,_iO_j
Characterized in that the nanoparticles are NiO nanoparticles
It The invention according to claim 6 is the magnetic according to claim 2.
A method for producing nanoparticles, comprising FeX_Two・ NH_TwoO
(X: all halogen elements, all positive fruits including n: 0
Number) and Na_TwoSiO_Three・ MH_TwoO (m: 0
(Including all positive real numbers), mix evenly and let stand.
To form a precipitate, wash the precipitate and dry.
And calcination at 780 ° C. to 800 ° C. Well
The invention according to claim 7 is the magnetic nanoparticle according to claim 3.
A method for producing particles, comprising FeX_Two・ NH_TwoO (X: All
All halogen elements, all positive real numbers including n: 0)
Solution and Na_TwoSiO_Three・ MH_TwoO (all including m: 0
Positive real number) and then CoX_Two・ QH
_TwoO (X: all halogen elements, all positive including q: 0
Solution) and mix evenly, leave to settle.
The precipitate is formed, the precipitate is washed, dried and then 8
It is characterized by firing at 00 ° C to 850 ° C. Also,
The invention according to claim 8 is the magnetic nanoparticle according to claim 5.
The manufacturing method of_Two・ NH_TwoO (X: All
Halogen element, all positive real numbers including n: 0)
Liquid and Na_TwoSiO_Three・ MH_TwoO (all positives including m: 0
Solution) containing the same number) and then left to stand to form a precipitate.
The precipitate is washed, dried and dried at 650 ° C.
It is characterized by firing at 1000 ° C. Also, the present invention
The magnetic nanoparticle thin film according to claim 9,
1. The magnetic nanoparticles according to 1 are contained.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic nanoparticles of the present invention are MX
_p・ NH_TwoO (M: transition metal or rare earth metal, X: all
All positive elements including all halogen elements, p and n: 0
Number) and Na_TwoSiO_Three・ MH_TwoO (m: 0
By including a solution containing all positive real numbers)
Amorphous SiO obtained by firing the formed precipitate
_Two+ M _iO_j(I and j are integers from 1 to 9)
Fine particles that are individual M_iO_jAmorphous nanoparticles
Fas SiO_TwoHolds separated by a reticular membrane
It is characterized by being. Conventional manufacturing method
The magnetic fine particles obtained by
When aggregated, it aggregates into lumps consisting of several hundred or more units of fine particles.
It is had. Therefore, in order to prevent this phenomenon
Is a process of coating individual particles with an isolation film after particle generation.
However, the effect is always satisfactory.
Rather, form a population of fine particles of at most tens of units
It could only be separated up to the end. Yo
Therefore, in the conventional magnetic recording material, the population is the smallest.
Since it was a unit, one information item for each group
I could only record it. Therefore, 2.5 in
Tens of gigabytes converted to the storage capacity of the hard disk
Is considered to be the performance limit of magnetic recording materials.
It was The above-mentioned JP 2001-261A established by the present inventors.
The manufacturing method described in Japanese Patent No. 334 discloses performance of magnetic recording materials.
The magnetic fine particles of the present invention make a big leap.
The individual fine particles are amorphous SiO from the beginning of formation._Two
Since it is held in a separated state by the mesh film,
Requires a step of covering each individual particle with an isolation film
No information is recorded for each magnetic particle.
Can be recorded. Therefore, as a magnetic recording material,
The following functions are being improved.

M _i O constituting the magnetic nanoparticles of the present invention
M in the _j nanoparticles is selected from Cr, Fe, Co, Ni and the like. The individual M _i O _j nanoparticles form a single ferromagnetic domain, and the Hc (coercive force) at room temperature is larger than that of the conventional one. Further, Hc can be increased by doping with, for example, Si, Co, Os or the like.

A typical method for producing the magnetic nanoparticles of the present invention
The outline of the method will be described below. First, metal halo
Genide MX_p・ NH_TwoO-containing solution and (meth) silicate
Thorium Na_TwoSiO_Three・ MH_TwoFor example, a solution containing O
For example, mix at room temperature for a specified time and then leave it for a specified time.
By this, amorphous SiO_TwoMetal hydroxide in reticulated film
M_i(OH)_jA precipitate in which nanoparticles are dispersed is obtained. M
X_p・ NH_TwoO and Na _TwoSiO_Three・ MH_TwoO mixture is equal
It is preferably carried out in molar amounts. Wash the resulting precipitate
When dried from, it becomes a glassy mass. Powder this
After crushing, baking in an air atmosphere gives
Oxide M_i(OH)_jNano-particles as metal oxide M_iO_j
Change to nanoparticles. Optimize firing temperature at this time
Individual M_iO_jAmorphous S nanoparticles
iO_TwoMagnetism held separated by a reticulated membrane
Use nanoparticles. The optimum firing temperature is, for example, M_i
O _jFe nanoparticles_TwoO_ThreeIn case of nanoparticles
It is 780 ° C to 800 ° C. When fired at this temperature,
Fe_TwoO_ThreeNanoparticles have high coercive force and remanent magnetization at room temperature.
Having γ-Fe_TwoO_ThreeAnd α-Fe_TwoO_ThreeCoexistence with nano
Composed of particles. Further, in the case of NiO nanoparticles,
It is 650 ° C to 1000 ° C. The firing time is 3 hours
The above is preferable.

Magnetic nanoparticles, which are Fe ₂ O ₃ nanoparticles in which M _i O _j nanoparticles are Co-doped, are, for example, a solution containing FeCl ₂ .4H ₂ O and Na ₂ SiO _3.
After mixing the solution containing 9H ₂ O, CoCl ₂ · 6H
A solution containing ₂ O is added to the amorphous S, for example, by uniformly mixing at room temperature for a predetermined time and then allowing it to stand for a predetermined time.
A precipitate in which Co _x Fe _1-x (OH) ₃ nanoparticles are dispersed in the iO ₂ network film is obtained. FeCl ₂ · 4H ₂ O and N
The mixture of a ₂ SiO ₃ .9H ₂ O and CoCl ₂ .6H ₂ O has a Co / Fe molar ratio of 0.05 to 0.5 and Si /
The molar ratio of (Fe + Co) is preferably 0.9 to 1.1. The obtained precipitate becomes a glassy mass by washing and then drying. After crushing this, it is baked in an air atmosphere to give Co _x Fe _1-x (O
H) ₃ nanoparticles are converted into (Co _x Fe _{1- x} ) _i O _j nanoparticles, that is, Co-doped Fe ₂ O ₃ nanoparticles. The firing temperature at this time is 800 ° C to 850
℃, the individual Co-doped Fe ₂ O
_{The 3} nanoparticles are magnetic nanoparticles held in a state of being separated by an amorphous SiO ₂ network film. When calcined at the above temperature, Fe ₂ O ₃ nanoparticles have high coercive force and residual magnetization at room temperature, γ-Fe ₂ O ₃ and α-F.
It consists of nanoparticles that coexist with e ₂ O ₃ . The firing time is preferably 3 hours or more.

The magnetic nanoparticles of the present invention can be solidified in a medium known per se and molded into an arbitrary shape for use. The solution containing the MX _p · nH ₂ O and _Na 2 _SiO 3 · m
If the substrate is immersed in a mixed solution in which a solution containing H ₂ O is uniformly mixed, then pulled up, dried and then baked at an optimum temperature, individual M _i O _j nanoparticles are formed into amorphous SiO ₂ particles.
It is possible to produce a magnetic nanoparticle thin film containing magnetic nanoparticles that are held in a separated state by a mesh film. In addition to the dip coating method as described above, a spray drying method, a spin coating method, or the like can be used for manufacturing the magnetic nanoparticle thin film. Further, the two stacked substrates are vertically placed so that their lower parts are immersed in the above-mentioned mixed solution, so that the mixed solution is infiltrated between the substrates and baked at an optimum temperature after drying. Thus, the magnetic nanoparticle thin film may be formed between the substrates. Further, by producing the magnetic nanoparticle thin film in an arbitrary magnetic field, it is possible to improve the characteristics in terms of residual magnetization and saturation magnetization.

[0010]

The present invention will be explained in more detail by the following examples, but the present invention is not limited thereto.

Example 1: 0.1 mol FeCl_Two・ 4H
_TwoAqueous solution containing O and 0.1 mol Na_TwoSiO _Three・ 9H
_TwoStir the aqueous solution containing O in a container at room temperature.
After uniformly mixing for 5 to 10 hours with further stirring, 24 to
Let stand for 48 hours or use a centrifuge for 10
Precipitate in a container by centrifugation for ~ 30 minutes.
After being generated, this precipitate was washed with pure water. This wash
If the concentration of impurities contained in the wash water is 1/10 of the original
It was carried out until it became less than 00, and then it was left to stand at room temperature to dry.
When dried, a glassy mass was obtained. This glass
The lumps were placed in a mortar and crushed into powder.

The obtained powder was heated in air at 800 ° C. for 7 hours.
By firing in an electric furnace at_TwoO
_ThreeAmorphous SiO nanoparticles_TwoMinute by reticulated membrane
The magnetic nanoparticles that were held in a separated state were obtained.
Individual Fe_TwoO_ThreeAmorphous SiO nanoparticles_Twonetwork
To be held separated by a membrane
Fe is determined by measuring the powder X-ray diffraction pattern._TwoO_ThreeNa
Fine particles and amorphous SiO_TwoOf coexistence
Confirmation, Fe from transmission electron microscope image_TwoO_ThreeNanoparticles and F
e_TwoO_ThreeAmorphous SiO between nanoparticles_TwoLayer exists
Confirmation of existence (see Fig. 1) and X-ray absorption fine structure
Fe by measurement_TwoO_ThreeAdjacent regions of Fe atoms in nanoparticles
No Si atoms exist in the region, that is, amorphous S
iO_TwoIs Fe_TwoO_ThreeOf being outside the nanoparticles
I went from confirmation. From the half-width diffraction angle width of the X-ray diffraction peak
Fe using the Debye-Scherrer formula_TwoO_ThreeFlat nano particles
The average particle size was calculated to be about 3 nm. Also transparent
Fe from electron microscope image_TwoO _ThreeThe maximum particle size of nanoparticles
When measured, it was 5 nm. Obtained magnetic nano particles
Evaluation of a magnetic recording material as a magnetic recording material at room temperature
Therefore, when I went, I found a coercive force of about 1 kilo Oersted.
It had a remanent magnetization of about 10 emu / g. This high protection
Magnetic force and remanent magnetization are Fe_TwoO_ThreeNano particles are γ-Fe_Two
O_ThreeAnd α-Fe_TwoO_ThreeCoexisting with
It was speculated to be due to this. The firing temperature is below 780 ° C.
When turning, γ-Fe_TwoO_ThreeThe ratio of nanoparticles increases and the
The magnetic force tended to decrease. Sun baked at 650 ° C
Pull is γ-Fe _TwoO_ThreeCoercive force consisting only of nanoparticles
Didn't have. On the other hand, the firing temperature exceeds 800 ° C
And the remanent magnetization tends to decrease, so firing at 860 ° C
The sample does not have nanoparticles, and α-Fe_TwoO_Three
And SiO_TwoEach containing only bulk crystals of
It was.

Example 2: 0.075 mol of FeCl ₂
An aqueous solution containing 4H ₂ O and 0.1 mol of Na ₂ SiO ₃ ·.
An aqueous solution containing 9H ₂ O was mixed at room temperature with stirring with a stirrer in a container, and then an aqueous solution containing 0.025 mol of CoCl ₂ .6H ₂ O was added to the solution,
After uniformly mixing for 5 to 10 hours, the mixture was allowed to stand for 24 to 48 hours, or was centrifuged for 10 to 30 minutes using a centrifuge to generate a precipitate in a container. This precipitate was washed with pure water. This washing operation was performed until the concentration of impurities contained in the washing water was 1/1000 or less of the initial concentration, and then the mixture was allowed to stand at room temperature and dried, whereby a glassy lump was obtained. This glassy lump was placed in a mortar and crushed into powder.

The obtained powder was fired at 800 ° C. for 10 hours in air using an electric furnace, whereby individual Co-doped Fe ₂ O ₃ nanoparticles were formed into amorphous SiO 2.
We obtained magnetic nanoparticles that were held separated by _two mesh films (individual Co-doped Fe ₂ O ₃
It was confirmed by the same method as in Example 1 that the nanoparticles were held in a state of being separated by the amorphous SiO ₂ network film). The magnetic nanoparticles are composed of C
The average particle size of the o-doped Fe ₂ O ₃ nanoparticles is about 4
nm (by the same measurement as in Example 1), Example 1
Similar to the magnetic nanoparticles obtained in 1., it showed an excellent function as a magnetic recording material.

Example 3: 0.1 mol of NiCl_Two・ 6H
_TwoAqueous solution containing O and 0.1 mol Na_TwoSiO _Three・ 9H
_TwoStir the aqueous solution containing O in a container at room temperature.
After uniformly mixing for 5 to 10 hours with further stirring, 24 to
Let stand for 48 hours or use a centrifuge for 10
Precipitate in a container by centrifugation for ~ 30 minutes.
Was generated. This precipitate was washed with pure water. This washing operation
The concentration of impurities contained in the wash water is 1/100 of the original
It went to 0 or less, then left to stand at room temperature to dry
As a result, a glass-like lump was obtained. This glassy
Was put into a mortar and crushed into powder.

The resulting powder was calcined at 800 ° C. for 10 hours in air using an electric furnace to obtain individual NiO.
Magnetic nanoparticles were obtained in which nanoparticles were held in a state of being separated by an amorphous SiO ₂ network film. (See that individual NiO nanoparticles are held in a state of being separated by an amorphous SiO ₂ network film in Examples. 1
Confirm in the same way as. This magnetic nanoparticle has an average particle diameter of NiO nanoparticle of about 3 nm (by the same measurement as in Example 1), and as a magnetic recording material like the magnetic nanoparticle obtained in Example 1. It showed excellent function.

[0017]

EFFECTS OF THE INVENTION According to the present invention, there are provided magnetic nanoparticles having improved functions as a magnetic recording material.

[Brief description of drawings]

FIG. 1 is a transmission electron microscope image photograph of magnetic nanoparticles obtained in Example 1.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 5/714 G11B 5/714 5/842 5/842 Z H01F 10/187 H01F 10/187 10/20 10/20 ( 72) Inventor Yukio Tatehana 64-8-205 F term (reference) 4-8-205 F term (reference) 4-8-205 F term (reference), Hodogaya-ku, Yokohama, Kanagawa Prefecture AA01 AB03 AC01 BA06

Claims (9)

[Claims] 1. A _{MX p · nH 2 O (M} : transition metal or rare earth metal, X: All halogen, p and n: 0
Including all positive real numbers) and Na ₂ SiO ₃ ·
Amorphous SiO ₂ + M _i O _j (i, j is 1 to 9) obtained by calcining a precipitate generated by uniformly mixing a solution containing mH ₂ O (all positive real numbers including m: 0) Magnetic nanoparticles, each of which has an individual M _i O _j
Magnetic nano-particles, characterized in that the nanoparticles are held in a state of being separated by an amorphous SiO ₂ network film. 2. The magnetic nanoparticles according to claim 1, wherein the M _i O _j nanoparticles are Fe ₂ O ₃ nanoparticles. 3. The magnetic nanoparticles according to claim 1, wherein the M _i O _j nanoparticles are Co-doped Fe ₂ O ₃ nanoparticles. 4. Fe ₂ O ₃ nanoparticles are γ-Fe ₂ O ₃
The magnetic nanoparticles according to claim 2 or 3, which are nanoparticles coexisting with α-Fe ₂ O ₃ . 5. The magnetic nanoparticles according to claim 1, wherein the M _i O _j nanoparticles are NiO nanoparticles. 6. A solution containing FeX ₂ .nH ₂ O (X: all halogen elements, all positive real numbers including n: 0) and N.
A solution containing a ₂ SiO ₃ .mH ₂ O (all positive real numbers including m: 0) was uniformly mixed and allowed to stand to produce a precipitate, which was washed and dried before 780 ℃ ~ 80
The method for producing magnetic nanoparticles according to claim 2, wherein the method is firing at 0 ° C. 7. A solution containing FeX ₂ .nH ₂ O (X: all halogen elements, all positive real numbers including n: 0) and N.
After mixing a solution containing a ₂ SiO ₃ .mH ₂ O (all positive real numbers including m: 0), CoX ₂ .qH ₂ O
A solution containing (X: all halogen elements, all positive real numbers including q: 0) is added and uniformly mixed, and allowed to stand to form a precipitate, which is washed and dried. To 800
The method for producing magnetic nanoparticles according to claim 3, wherein the firing is performed at a temperature of from ℃ to 850 ℃. 8. A solution containing NiX ₂ .nH ₂ O (X: all halogen elements, all positive real numbers including n: 0) and N.
A solution containing a ₂ SiO ₃ .mH ₂ O (all positive real numbers including m: 0) was homogeneously mixed and allowed to stand to produce a precipitate, which was washed and dried before 650 ℃ ~ 10
The method for producing magnetic nanoparticles according to claim 5, which comprises firing at 00 ° C. 9. A magnetic nanoparticle thin film containing the magnetic nanoparticles according to claim 1.