JPH04278204A - Magnetic head - Google Patents

Abstract

PURPOSE:To prevent a track width and gap depth of magnetic gap from being smaller than the predetermined values by erosion of metal magnetic material by a glass which is joining a pair of half bodies of magnetic core. CONSTITUTION:In a magnetic head, wherein at least one of the half bodies of the first and second magnetic core half bodies 1, 1' is provided with a metal magnetic thin film 3 and the first and second magnetic core half bodies 1, 1' are joined by a glass 5 in contact with metal magnetic thin film 3 to form a magnetic gap 2, a ratio A/B, where A is composition of BO1.5 in the glass 5 and B is sum of compositions of NaO0.5 and KO0.5 is set to 3.1 or less.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head used in a magnetic recording device such as a VTR.

0002

BACKGROUND OF THE INVENTION In recent years, in magnetic recording and reproducing devices such as VTRs, MIG (Metal In Ga), in which a magnetic thin film of metal such as FeAlSi alloy (Sendust) is formed near the gap, is used as a magnetic head due to the increase in recording density.
A p) type magnetic head has been developed.

The MIG type magnetic head has various shapes as shown in FIGS. 1, 2, 3, and 4, respectively. In the figure, 1 and 1' are a pair of first and second magnetic core halves made of an oxide magnetic material such as Mn-Zn ferrite, and 2 is a magnetic gap. , 1' near the magnetic gap 2 is a metal magnetic thin film 3,
3 is formed by adhesion. 4 is a winding groove; 5 and 5 are glasses for bonding and fixing the first and second magnetic core halves 1 and 1';
is in contact with. In the magnetic head having such a structure, the working temperature when joining the first and second magnetic core halves 1, 1' by melting the glasses 5, 5 is the same as that of the metal magnetic thin films 3, 3. In consideration of thermal properties, the temperature is usually set at 600°C or lower, and to lower the melting point of glasses 5 and 5, a glass containing B2O3 is used instead of SiO2.

However, in the MIG type magnetic head as described above, when the first and second magnetic core halves 1 and 1' are bonded and fixed, the metal magnetic thin film 3 is
, 3 are eroded, and the collection of atoms of the metal magnetic thin films 3, 3 melts into the glasses 5, 5.
becomes magnetic, causing a problem of demagnetizing the magnetic recording medium, or the track width or gap depth of the magnetic gap 2 becomes smaller than a predetermined value, causing a problem of deterioration of magnetic properties.

As a magnetic head that eliminates the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. 172203/1983 (G11B
5/127) and Japanese Unexamined Patent Publication No. 145512/1983 (G
11B5/127), a magnetic head has been proposed in which the metal magnetic thin film is prevented from being eroded by glass by providing a reaction prevention film made of SiO2, Cr, etc. on the metal magnetic thin film. However, in this magnetic head as well, forming a reaction prevention film on the metal magnetic thin film leads to an increase in the number of steps in the manufacturing process, resulting in an increase in cost.

It is also possible to increase the track width and gap depth of the magnetic gap in advance in consideration of the erosion of the glass into the metal magnetic thin film, but the degree of erosion of the glass is unstable, and this method is Not practical.

[0007]

[Problems to be Solved by the Invention] The present invention has been made in view of the drawbacks of the above-mentioned conventional examples. It is an object of the present invention to provide a magnetic head that prevents the track width or gap depth of the magnetic gap from becoming smaller than a predetermined value.

[0008]

[Means for Solving the Problems] The present invention provides a method in which at least one of a pair of magnetic core halves includes a metal magnetic material, and the pair of magnetic core halves are brought into contact with the metal magnetic material. BO1 in the glass is bonded to form a magnetic gap.
．． The ratio (A/B) between the composition (A) of No. 5 and the sum of the compositions of NaO0.5 and KO0.5 (B) is 3.1 or less.

[0009]

[Function] Glass with the above composition has a small proportion of B2O3, which causes corrosion to metal magnetic materials, and a large proportion of Na2O and K2O, which act to prevent corrosion.
Erosion of the glass into the metal magnetic material is suppressed.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic head of the present invention will be explained in detail below.

[0011] In this example, the degree of corrosion of the metal magnetic material was investigated for the glasses a to n having the compositions shown in Table 1 below.

0012

[Table 1]

[0013] The degree of glass erosion is Fe-Al-
Si-based metal magnetic material (in this example, Fe: 82.55
wt%, Al: 7.11 wt%, Si: 9.70 wt%
, Cr: 0.64 wt%), a glass rod having the composition of the above sample was placed, and after applying temperature in the same temperature cycle as the glass welding process when joining the first and second magnetic core halves. The surface roughness was determined by removing the glass and measuring the surface condition of that part using a surface roughness meter.

[0014] As a result of examining the erosion of the glass of the above-mentioned samples a to n against the metal magnetic material, it was found that the erosion of the glass is largely related to the amounts of B2O3, K2O, and Na2O in the composition of the glass.

Table 2 shows the BO1. of the glasses of samples a to n above.
Composition (A) of No. 5 and alkali metal element oxide, namely NaO
0.5 and the total composition (B) of KO0.5 (A/B
) and the degree of erosion of the glass to the metal magnetic material. In addition, NaO0.5, KO0.5, FeO in Table 2
1.5, BO1.5, AlO1.5 means 1/2 Na2
0, 1/2K2O, 1/2Fe2O3, 1/2B2O3
, 1/2Al2O3.

[0016]

[Table 2]

As can be seen from Table 2, in the glasses of samples f, k, and l whose ratio (A/B) is 3.1 or less, the degree of erosion is 1.0 or less, and the glass becomes a metallic magnetic material. There is almost no erosion.

That is, when there is a large amount of BO1.5 in the glass, the crystal structure or bonding structure of the glass changes significantly near the working temperature in the glass welding process, and the metal magnetic material is eroded. This phenomenon occurs when B, a constituent element of glass, is present in excess in the glass, and the excess B bonds and O react with the elements of the metal magnetic material, causing the metal magnetic material to erode and become non-magnetic. This is thought to be due to the The above reaction is prevented by alkali metal elements such as KO0.5 and NaO0.5, and by adding or increasing the composition of these alkali metal elements, the erosion of the metal magnetic material by glass can be prevented. Can be made smaller.

[0019] In the Fe-Al-Si alloy,
Its compositional elements include Al, which is famous for being easily oxidized by thermite reactions, etc., and when this reacts with oxygen contained in the glass, the relative amount of Al decreases, and Fe-Al - Various properties of the Si-based alloy deteriorate. In the glass of the present invention, by reducing the amount of BO1.5, B or O in the glass and Fe-Al-
Reaction with Al in the Si-based alloy is prevented.

[0020]

[Effects of the Invention] According to the present invention, the erosion of the glass into the metal magnetic material is suppressed, the track width of the magnetic gap and the gap depth are prevented from becoming smaller than a predetermined value, and good recording and reproduction can be performed. It is possible to provide a magnetic head that can perform

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the appearance of a magnetic head.

FIG. 2 is a perspective view showing the appearance of the magnetic head.

FIG. 3 is a perspective view showing the appearance of the magnetic head.

FIG. 4 is a perspective view showing the appearance of the magnetic head.

[Explanation of symbols]

1 First magnetic core half 1’ Second magnetic core half 2 Magnetic gap 3 Metal magnetic thin film 5 Glass

Claims (2)

[Claims] 1. At least one of the pair of magnetic core halves includes a metal magnetic material, and the pair of magnetic core halves are joined together by glass that contacts the metal magnetic material to form a magnetic gap. In the magnetic head formed, the composition (A) of BO1.5 in the glass and the N
The ratio (A) of the sum of the compositions of aO0.5 and KO0.5 (B)
/B) is 3.1 or less. 2. The magnetic head according to claim 1, wherein the metal magnetic material is made of a Fe-Al-Si alloy.