JPH03272104A - Magnetic recording powder - Google Patents

Abstract

PURPOSE:To lower the Curie point, and also to improve the coercive force at the normal temperature by a method wherein Mn, Al and Cr are added to the alloy containing at least a kind selected from Y and rare-earth element and the remainder consisting of Fe and inevitable impurities. CONSTITUTION:An alloy, containing at least a kind (indicated by R) selected from Y and a rare-earth element of 5 to 20 atomic % and B of 5 to 20 atomic % and the remaining part having the composition consisting of Fe and inevitable impurities, is prepared. Alloy powder is obtained by adding the alloy powder formed by adding Mn of 4 to 20 atomic % to the above-mentioned alloy, or formed by adding one or two kinds selected from Al of 1 to 10 atomic % and Cr of 1 to 10 atomic %, to Mn of 4 to 20 atomic %. As a result, coercive force can be enhanced sufficiently when the above-mentioned alloy powder is used as magnetic recording powder, and sufficient effect can be obtained even when Mn, Al and Cr are added not according to the condition. Accordingly, the energy used for heating up to the Curie point can be reduced, and the heating device can be miniaturized in a simple manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording powder that has a high coercive force at room temperature and a low Curie point, and is used for manufacturing magnetic recording media such as magnetic tapes and magnetic cards. It is something.

[Conventional technology]

Conventionally, γ-Fe203 powder, Ba
Ferrite powder, RCos powder (R is a type of rare earth element including Y, and 5111 is mainly used), Nd-Fe-B alloy powder (JP-A-5
9-229461) and the like are known. The coercive force (iHc) and Curie point (Tc) of these magnetic recording powders at room temperature are approximately as shown in Table 1.

A magnetic recording medium such as a magnetic tape or a magnetic card is manufactured by applying these magnetic recording powders to the surface of a tape or a synthetic resin plate, respectively. The recording powder was heated to a temperature just below its Curie point, and normal magnetic writing and erasing was performed in a state where the coercive force was weakened.

[Problem to be solved by the invention]

As mentioned above, in order to perform normal magnetic writing and erasing, it is necessary to heat a magnetic recording medium such as a magnetic tape or a magnetic card to a temperature just below the Curie point of the magnetic recording powder. All of these magnetic recording powders have high Curie points, so they require a large amount of energy to heat up. For this reason, research into magnetic recording powders with low Curie points has been progressing, but generally speaking, when the Curie point is lowered, the coercive force at room temperature also decreases at the same time.

[Means to solve the problem]

Therefore, the present inventors conducted research to develop a magnetic recording powder that lowers the Curie point and at the same time has a high coercive force at room temperature. = 5 to 20 atomic %, B: 5 to 20 atomic %, and the remainder is Fe and inevitable impurities, and Mn: 4 to 20 atomic % is added to an alloy powder, or Mn: 4 to 20 at% and further AD: 1 to lO
They have found that an alloy powder made by adding one or two of atomic % and 1 to 10 atomic % of Cr becomes a magnetic recording powder that has a high coercive force and a low Curie point at room temperature.

This invention was made based on such knowledge, and contains (a) R: 5 to 20 atom%, B: 5 to 20 atom%, and further Mn: 4 to 20 atom%, (b) R: 5 to 20 at%, B: 5 to 20 %, furthermore, contains Mn: 4 to 20 atomic %, and further contains Al: 1 to 10 atomic %, and Cr: 1 to 10 atomic %.
The magnetic recording powder is characterized by having a composition containing one or two of these, with the remainder consisting of Fe and unavoidable impurities, and having a high coercive force at room temperature and a low Curie point.

Next, the reason for limiting the component composition of this invention as described above will be explained.

(1), Y and at least one rare earth element: R R is Nd, Pr, La, Ce, Tb, Dy.

Ho, Er, Eu, Sm, Gd, Pr, T+n.

It consists of one or more types of Yb and Y, and among them, Nb and Dy are particularly preferred. If the R content is less than 5 at%, a large amount of cubic crystal structure having the same structure as α-iron will appear, making it impossible to obtain a good coercive force, which is undesirable.On the other hand, if the R content exceeds 20 at%, Also, R-rich nonmagnetic phase increases, which causes problems of decreased saturation magnetization and oxidation, which is not preferable.

Therefore, the content of R was set at 5 to 20 atomic %.

(2), B If the content of B is less than 5 atomic %, it becomes a substrate structure, making it impossible to obtain a good coercive force, which is undesirable.On the other hand, if the B content exceeds 20 atomic %, saturation magnetization This is not preferable because the magnetic field decreases and coercive force cannot be obtained.

Therefore, the content of B was set at 5 to 20 at%.

(3), Mn Mn has the effect of lowering the Curie point when contained in the R-B-Fe magnet alloy, but if its content is less than 4 at%, this effect will not appear; If the content exceeds atomic percent, the coercive force at room temperature will decrease, which is not preferable.

Therefore, the Mn content was set at 4 to 20 at%.

(4), Aρ and Cr By adding one or two of Aρ and Cr together with Mn to the R-B-Fe-based magnetic alloy, it has the effect of further lowering the Curie point. If the amount is less than 1 at%, the effect will not be noticeable;
If the content exceeds 0 at%, the coercive force at room temperature will decrease,
Undesirable.

Therefore, the content of Aρ and Cr was determined to be 1 to 10 atomic %.

However, in order to add one or two of Aρ and Cr together with Mn, 4 at.%≦Mn+Al +Cr≦
It is necessary to add so as to satisfy the condition of 20 atomic %.

〔Example〕

As raw materials, pure iron, metal Nb, metal Dy, FC-B alloy (B: 20%), Fe-Mn alloy (Mn: 75%)
.

Fe-Al1 alloy (Aρ: 50%) and Fe-Cr
An alloy (Cr: 80%) was prepared, and these raw materials were melted and cast in a high frequency melting furnace to produce rare earth alloy ingots having the compositions shown in the Examples and Comparative Examples in Table 2.

These rare earth alloy ingots are coarsely pulverized using a stamp mill in an Ar gas atmosphere, and then finely pulverized using a vibrating ball mill to obtain rare earth alloy fine powder, and an appropriate amount of this rare earth alloy fine powder is charged into a boat and heated in a heat treatment furnace. into 0. IX
After evacuating to a vacuum of 10'Torr, 1 atn of hydrogen gas was introduced into the furnace, and the temperature was raised from room temperature to 850°C while maintaining the hydrogen gas pressure, and when it reached 850°C, this temperature was While maintaining the temperature, the atmosphere in the heat treatment furnace was evacuated for 30 minutes, and the atmosphere in the heat treatment furnace was reduced to 1. A vacuum of OX 10'Torr was applied.

Thereafter, Ar gas was allowed to flow into the furnace until the temperature reached 1 atIm to rapidly cool the fine powder. The aggregated fine powder was loosened with a mortar and further finely pulverized with a vibrating ball mill to obtain magnetic recording powder having the average particle size shown in Table 2.

The coercive force (iH
c) and Curie point (Tc) were measured and the results are shown in Table 2.

〔Effect of the invention〕

From the results in Table 2, the Curie point of the magnetic recording powder of the present invention is lower than the Curie point of the conventional magnetic recording powder shown in Table 1, and the coercive force at room temperature is suitable for use as a magnetic recording powder. It can be seen that this is sufficiently high. Furthermore, it can be seen that sufficient effects cannot be obtained even if Mn, A(1, and Cr are contained outside the conditions of this invention) (
Note that in Table 2, values outside the conditions of this invention are marked with *. ).

Therefore, a magnetic recording medium such as a magnetic tape or a magnetic card produced using the magnetic recording powder of the present invention requires less energy to heat to just below the Curie point, and the equipment for heating it to a temperature that is smaller can be used. Since it can be made simple, it has excellent effects in terms of energy saving and industry.

Claims (4)

[Claims] (1) Contains at least one of Y and a rare earth element (hereinafter referred to as R): 5 to 20 atomic %, B: 5 to 20 atomic %, and further contains Mn: 4 to 20 atomic %. A magnetic recording powder having a high coercive force at room temperature and a low Curie point, the balance being Fe and unavoidable impurities. (2) Contains R: 5 to 20 atomic%, B: 5 to 20 atomic%, and further contains Mn: 4 to 20 atomic%, Al: 1 to 10 atomic%, and the remainder is Fe and unavoidable A magnetic recording powder having a high coercive force at room temperature and a low Curie point, characterized by having a composition consisting of impurities. (3) Contains R: 5 to 20 atomic%, B: 5 to 20 atomic%, and further contains Mn: 4 to 20 atomic%, Cr: 1 to 10 atomic%, and the remainder is Fe and unavoidable A magnetic recording powder having a high coercive force at room temperature and a low Curie point, characterized by having a composition consisting of impurities. (4) Contains R: 5 to 20 at%, B: 5 to 20 at%, and further contains Mn: 4 to 20 at%, Al: 1 to 10 at%, Cr: 1 to 10 at%. 1. A magnetic recording powder having a high coercive force at room temperature and a low Curie point, characterized by having a composition in which the remainder consists of Fe and unavoidable impurities.