JPH0453206A - Ferromagnetic material - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics by a method wherein an A-site occupying element contains a 3-A group element, and a B-site occupying element contains the transition element other than the 3A group element, and a B-site occupying element contains the transition element other than the 3A group element. CONSTITUTION:An A-site contains a 3A group element, a B-site contains the transition element other than the 3A group element, and the A-site has a defect. The A-site contains Y and Lanthanides elements at least a 3A group element selected from the groups of Ca, Sr and Ba, and alkaline earth metal, and the B-site contains at least a transition element selected from the group of Cr, Mn, Fe and Co. Also, the above-mentioned elements have the perovskite-type crystal structure indicated by the formula LaxMnO3-delta (0.85<=x<=0.96, delta is a positive infinitesimal values), a formula (La1-yEy)xMnO3-delta (E is alkaline earth metal, 0.85<=x<=0.96, 0<=y<=1, delta is a positive infinitesimal value), a formula (La1-ySry)xMnO3-delta (0.85<=x<=0.96, 0.24<=y<=0.50, delta is a positive infinitesimal value). The average ion radius of the B-site is smaller than the allowable maximum value of crystal structure of this material.

Description

[Detailed description of the invention] “Industrial Application Area The present invention relates to ferromagnetic materials.

[Problems to be solved by conventional technology and invention] G, H
, Jonker et al. reported that the following composite oxide material with a perovskite crystal structure exhibits ferromagnetism (Physica).

XX1. I, 707-722.1.956).

L a Cr 03 L a M n 03 L a Fe Oa (L a Ca ) M n, Osl, -3
1y (0,50≦y≦0.95) (La Sr )MnO3 1, -Y Y (0,30≦y≦0.90) (La Ba )MnO8 by y (0,50≦y≦0.95 ) La (M[l C" )03 z Z (0,1,0≦Z≦0.50) (La Ba) (Mn Ti)
031-y y 1-y
y (0,10≦y≦0.25) However, in all of the above ferromagnetic materials in the same report, the number of atoms of the element occupying the A site and the element occupying the BziI of the perovskite crystal structure is were equal.

Now, according to the same report, the magnitude of saturation magnetization, which is the magnetic property, is determined by the formula (L a,
E) MnOs (E is Ca, Sl, -y
The material represented by y r or Ba) has the largest value, which is approximately 06 W b /m 2 . However, the saturation magnetization measurement in the same report was carried out at liquid hydrogen temperature (20°4K), and the value at room temperature is estimated to be smaller than this. Moreover, the magnitude of saturation magnetization of approximately 0.06 W b / m 2 is within the range of 32 to 0,34 W b obtained for ferrite-based ferromagnetic materials at room temperature.
/ m 2 and had low practical value.

One object of the present invention is to provide a perovskite crystal material (a composite oxide with a 1η structure and a ferromagnetic material with excellent magnetic properties comparable to ferrite materials).

[Means for Solving the Problems and Their Effects] The ferromagnetic material according to the present invention is a composite oxide having a perovskite type crystal structure, in which the elements occupying the A site include group 3A elements, and the B It is a material that contains transition elements other than group 3A elements and has A-site defects, and has excellent magnetic properties such as large saturation magnetization. Magnetism is generally expressed by superexchange interaction of B site ion-oxygen-B site ion.

It is known that the presence or absence of this interaction and its magnitude are determined by the magnitude of the orbital overlap integral.

In the ferromagnetic material 1 according to the present invention, the original FD of the A site
is smaller than the B site, indicating that the A site is defective. It is thought that the presence of this A-site defect reduces the lattice constant of the crystal and increases the overlap of orbits. It is desirable that the ratio of the number of atoms occupying the A site to the atoms occupying the B site is 0.9Q or less.

Y, which is a group 3A element, a lanthanoid, or a mixture thereof can be placed at the A site.

In particular, it is preferable to employ La. In addition to group 3A elements, 7 /I
/ May contain potassium metals. As the added alkaline earth metal, Ca, Sr, Ba, or a mixture thereof can be employed.

A mixture of La and Sr is particularly preferred as the A site. On the other hand, C r SM, which is a transition element, is included in
n SF e or Co or a mixture thereof can be placed. Among them, Mn is preferable.

The following composition of ferromagnetic material having a perovskite crystal structure is particularly preferred. However, δ in each formula represents a minute oxygen defect.

LaxMnO3-δ3.

(0,85≦x≦0.96, δ is a positive minute value)
)(L a E ) Mn Oa,, -6
1, -y y・(n
) (L a, S r ) M n Os
−δt−y y x (0,85≦x≦0.96. 0,24≦y≦0.50, δ is a positive minute value) I
II) When the element occupying the A site is La or a mixture of La and an alkaline earth metal as in formula (I), (II) or (In), and the element occupying the B site is Mn, The atomic ratio of the A site to the B site, that is, the value of X in these three formulas, is 0.85 or more as above, 01
96 or higher. If the value of X is outside this range, a single phase material cannot be obtained. When Sr is added as an alkaline earth metal, the addition rate, ie, the value of y in formula (III), is set to be 0.24 or more and 0.50 or less. If the value of y is outside this range, ferromagnetism cannot be obtained.

In terms of the crystal structure, it is desirable that the average ionic radius of the element occupying the B site is smaller than the maximum allowable value for the material.

When the average ionic radius of the B site becomes smaller, the crystal distortion from the cubic crystal decreases, and the distortion of the angle of the B site ion-oxygen-B site ion involved in the above superexchange interaction decreases, resulting in the above-mentioned shape of the integral. It is expected that the value will increase. This can be confirmed by the fact that oxygen is not desorbed even when the material is heated from room temperature to 1200° C. in the atmosphere. In particular, when the element occupying the A site contains an alkaline earth metal in addition to the 3A group element, the ion average oxidation number of the element occupying the B site is determined by the atomic ratio between the A site and the B site and the alkaline earth metal. It is desirable that the material be determined only by the amount added.

For example, when Mn is used as the element occupying the B site, two types of ions, Mn and Mn, which has an ion half radius smaller than Mn, coexist in the same material. When a part of La 3+20 occupying the A site is replaced with, for example, Sr, 3+ is added to the B site in order to maintain the electrical neutrality of the entire material.
At 4+, the number of Mn decreases, while Mn increases at 2+. In other words, the addition of Sr 2 causes the average ionic radius of the B site to become smaller than the maximum value allowed by the crystal structure. Now, in order for the desorption of 10 ions to occur, Mn must increase and Mn must decrease so as to maintain the electrical neutrality of the entire material. However, as mentioned above, based on the amount of Sr added, 3+
If the ion number ratio between M r+ and Mn of 4+ is determined, Mn cannot increase. therefore,
Oxygen desorption does not occur even if the temperature of the material is increased.

[Example] Hereinafter, the formula (La Sr ) Mn03-δ1-
y y X (0,85≦x≦0.96.0.24≦y≦O150%
An example of a ferromagnetic material having a perovskite crystal structure represented by δ (a positive infinitesimal value) will be described.

(Example 1) When x=0.94, yxQ, 31. That is, (L
a S r ) M n 00.69
0.310.94 3-δ0 First, the manufacturing method will be explained.

L a OSS r Co-M n Coa (purity 99.99%) was used as a starting material, and these raw materials were blended at a predetermined ratio. However, the water content was corrected by plasma emission spectrometry (ICP). After thoroughly mixing the mixture in an agate mortar, it was calcined in air at 1,273 K for 15 hours. This was pulverized and further calcined at 1.573 K for 48 hours to obtain a powder having the above composition. This calcination temperature and time are sufficient to evaporate carbon dioxide gas, and the calcination temperature and time]
0 was sufficient to promote the reaction.

The obtained powder was dissolved in hydrochloric acid, and each compositional element was determined by ICP, and it was confirmed that the powder had the composition described in 1. In addition, the crystal structure was analyzed using powder X-ray diffraction. As shown in FIG. 1, only the peak of the perovskite crystal structure appears, indicating that it is a homogeneous phase.

The B-H curve in FIG. 2 measured by the vibrating sample method (VSM method) shows typical ferromagnetism with a magnetic history. The main magnetic property values are as follows.

Saturation magnetization Bs = 4707 Wb/m2 Residual magnetization Br - 1.604 W b / m 2 Coercive force Hc - 1,79 x 104 A/m The value of saturation magnetization Bs is M n - which is a typical ferrite-based ferromagnetic material. Approximately 0.34 for Z n ferrite
Wb/m2 or approximately 0.3 in the case of Ni-Zn ferrite
The size exceeds 2 Wb/m2. Also, residual magnetization B
r is large. However, it is a fully practical ferromagnetic material.

The results of thermogravimetric measurement using a thermobalance are shown in FIG. There was no significant weight loss when the temperature was raised from room temperature to 1400°C, indicating that no desorption of oxygen atoms in the components occurred.

When using the powder made of the above-mentioned ferromagnetic material as a permanent magnet material, the powder can be compacted in a magnetic field, and then the compact can be sintered for use. Powder molding may be performed using rubber or synthetic resin as a binder.

(Example 2) When x-0.94 and Y=0.21. That is, (La
Sr) Mn0O,790,210
, 943-60 A powder having the above composition was prepared in the same manner as in Example 1. B
-H curve is shown in FIG. Although it shows ferromagnetism,
±I X 1.07A/m (7) No magnetic saturation within the magnetic field strength range. The main magnetic property values are as follows.

Residual magnetization Br = 屹 0642 W b / m 2 Coercive force He - 1, 77 x 10' A/m Compared to Example 1, the residual magnetization Br is greatly reduced. Further, as a result of thermogravimetric measurement, a slight decrease in weight was observed as shown in FIG.

(Comparative Example 1) In the case of x-0,94, y-0,11. Sunai, (L
a Sr O, 890, 11) 0.94Mn03-6'Example]
A powder having the above composition was prepared in the same manner as above. The B-H curve is shown in FIG. It exhibits paramagnetism and no longer exhibits ferromagnetism. Further, as a result of thermogravimetric measurement, a significant weight reduction was observed as shown in FIG. Therefore, it cannot be used as a ferromagnetic material.

(Comparative Example 2) In the case of x-0,99, y-0,31. Sunaichi, (L
a Sr ) Mn0O, [i9 0.
31 0.99 3-60 The X-ray diffraction diagram is shown in FIG. As indicated by the symbol ■, La2O3 is precipitated and does not form a single phase. Therefore, it is unsuitable as a ferromagnetic material.

(Comparative Example 3) When x=0.84 and y=0.31. That is, (La
Sr) Mn00.6!1 0.3
1 0.84 3-60 X-ray diffraction pattern is shown in FIG. As indicated by the symbol ■, Mn2O3 emits tli and does not become ip, - phase. Therefore, it is unsuitable as a ferromagnetic material.

[Effect of the invention] As explained above, the ferromagnetic material according to the present invention has the following effects:
A complex oxide with a perovskite crystal structure,
The material that occupies the A site contains a group 3A element, the element that occupies the B site contains a transition element other than the group 3A element, and has an A site defect, and has excellent magnetic properties comparable to ferrite-based materials. Motsu. Therefore, the ferromagnetic material according to the present invention can be used, for example, as a magnet material or a material for magnetic recording.

[Brief explanation of the drawing]

FIG. 1 shows a ferromagnetic material (La
Sr) MnO X-ray 0.69
0.31 0.94 3-6 diffraction diagram, Figure 2 is a graph showing the B-H curve of the same material, Figure 3 is a chart showing the thermogravimetric measurement results of the same material, Figure 4 is the book Ferromagnetic material (L) according to another embodiment of the invention
a Sr ) 0.79 0. of MnO.
21 0.94 A graph showing the 3-δB-H curve.
1. Figure 6 is a graph showing the B-H curve of the material (La Sr0.89 0.11)O,94Mno according to the comparative example. Figure 7 is a chart showing the thermogravimetric measurement results of the same material. The figure shows materials related to other comparative examples (LaO, 69Sr
) X-ray diffraction diagram of MnO, 0.3+, 0.99
3-6 FIG. 9 shows materials according to still another comparative example (LaOfi'l
The X-ray diffraction diagram of S'0.31)0.84Mno is 3-δ. ]5

Claims (11)

[Claims] 1. A ferromagnetic material that is a composite oxide having a perovskite crystal structure, in which the element occupying the A site contains a group 3A element, the element occupying the B site contains a transition element other than the group 3A element, and has an A site defect. material. 2. 2. The ferromagnetic material according to claim 1, wherein the element occupying the A site contains at least one Group 3A element selected from the group consisting of Y and lanthanoids. 3. The elements occupying the B site are Cr, Mn, Fe, and Co.
3. The ferromagnetic material according to claim 1, comprising at least one transition element selected from the group consisting of: 4. 4. The ferromagnetic material according to claim 1, wherein the element occupying the A site contains an alkaline earth metal in addition to the Group 3A element. 5. Elements occupying the A site include Ca and S in addition to group 3A elements.
5. The ferromagnetic material according to claim 4, containing at least one alkaline earth metal selected from the group consisting of r and Ba. 6. Formula La_xMnO_3_-_δ(0.85≦x≦0
．． 96, δ is a positive infinitesimal value) A ferromagnetic material with a perovskite crystal structure. 7. Formula (La_1_-_yE_y)_xMnO_3_-
_δ (E is an alkaline earth metal, 0.85≦x≦0.96
, 0<y<1, δ is a positive infinitesimal value). A ferromagnetic material with a perovskite crystal structure. 8. Formula (La_1_−_ySr_y)_xMnO_3_
−_δ(0.85≦x≦0.96, 0.24≦y≦0.
A ferromagnetic material with a perovskite-type crystal structure expressed by 50, where δ is a positive infinitesimal value. 9. 9. The ferromagnetic material according to claim 1, wherein the average ionic radius of the element occupying the B site is smaller than the maximum allowable value according to the crystal structure of the material. 10. The ferromagnetic material according to any one of claims 1 to 8, wherein oxygen is not desorbed even when the temperature is increased from room temperature to 1200°C in the atmosphere. 11. Any one of claims 5 to 8, wherein the ion average oxidation number of the element occupying the B site is determined only by the atomic ratio between the A site and the B site and the amount of alkaline earth metal added.
Ferromagnetic materials described in Section.