JPH04132005A - Floating type magnetic head - Google Patents

Abstract

PURPOSE:To lower the base line noise of the waveforms of reproduced output and to improve the waveform shape thereof by incorporating specific ratios of ZrO2 and/or Nb2O5 as auxiliary components into Mn-Zn polycrystalline ferrite constituting a magnetic material core. CONSTITUTION:The ZrO2 and/or Nb2O5 as the auxiliary components are added to the Mn-Zn polycrystalline ferrite constituting the magnetic material core at 0.01 to 0.2wt.% (0.01 to 0.2wt.% in total if two kinds of the ZrO2 and Nb2O5 are incorporated) of weight % of the essential components (MnO, ZnO, Fe2O3). The floating type magnetic head which is small in the base line noise of the waveform of the reproduced output and has the good waveform shape is obtd. in this way.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a magnetic circuit using Mn-Zn polycrystalline ferrite having high magnetic permeability and a metal magnetic thin film having a saturation magnetic flux density higher than that of polycrystalline ferrite. Regarding monolithic floating magnetic heads used in high-frequency, high-density magnetic recording devices, we are particularly interested in floating magnetic heads that have low baseline noise during playback and good playback waveforms, and their magnetic The present invention relates to Mn-Zn polycrystalline ferrite constituting the head.

(Prior Art) A core slider consisting of a pair of magnetic cores as shown in FIGS. 1(a) and 1(b) is one of the floating magnetic heads used in magnetic recording devices for high frequency and high density recording. There is a monolithic type (for example, see Japanese Patent Laid-Open No. 14311/1983).

The monolithic floating type magnetic head l shown in FIGS. 1(a) and 1(b), for example, has an abutting surface between a C-type core 5 and a type-1 core 6, which are made of a pair of Mn-Zn polycrystalline ferrite magnetic materials. Fe-
Metal magnetic thin M4 such as AQ-5i system, magnetic gap G,
It consists of a reinforcing glass 7 and a winding (not shown) wound around the window 3 of the magnetic head 1.

In order to cope with the recent increase in the track density and linear recording density of magnetic recording media, the track width Tw and the gap length Gα of the magnetic gap portion have been significantly narrowed.

(Problem to be solved by the invention!) A floating magnetic head whose magnetic circuit is composed of Mn-Zn polycrystalline ferrite and a metal magnetic thin film has problems compared to a floating magnetic head which does not include a metal magnetic thin film. Therefore, it had the advantage of good recording and reproducing characteristics and little reduction in reproduction output, especially in areas where the recording current was large.

However, in order to cope with the recent increase in the track density of magnetic recording media, recent magnetic heads have significantly narrower tracks in the magnetic gap area, and there is a strong tendency for waveform fluctuations, that is, noise to occur. .

There is pseudo-gap noise as shown in FIG. 2(A), which is generated due to a difference in feel.

This pseudo gap noise is almost solved by forming a thin film of Cr or the like between the metal magnetic thin film and the ferrite core. (Unexamined Japanese Patent Publication No. 63-537067,
See Japanese Patent Laid-Open No. 63-298805, etc. Σ However, the baseline noise that occurs in the reproduced output waveform may be caused by the polycrystalline ferrite that makes up the main magnetic circuit, or whether it is caused by the metal that makes up the auxiliary magnetic circuit. It is not clear whether this is due to a magnetic thin film or glass or the like that joins the C-type core and I-type core, and the problem has not yet been resolved.

And when such baseline noise occurs,
The peak position of the main pulse fluctuates due to fluctuations in the output waveform due to noise, which increases the bit shift error and reduces the relative margin. As shown in Figure 3, the decrease in relative margin becomes noticeable when the track width is 20 μm or less, and becomes especially noticeable when the track width is 16 μm or less, which is a big problem for magnetic heads for high-density recording that aim for narrower tracks. It is becoming.

(Means for Solving the Problems) The present inventors have investigated baseline noise in reproduced waveforms, the cause of which is unknown, and have found that the noise position is located on a magnetic disk, which is a magnetic recording medium, as a characteristic of this noise. It was confirmed that it changes in almost inverse proportion to the rotation speed.

This fact suggests that the occurrence of baseline noise is related to the relative geometric arrangement of the magnetic disk and magnetic head.

Further, as a result of a detailed investigation of the magnetic head, it was confirmed that there is a strong tendency for the position of the grain boundary layer of polycrystalline ferrite to correspond to the position where noise is generated.

Therefore, based on the assumption that the grain boundary layer and the vicinity of the grain boundary layer have a pseudo-gap effect and that this is the cause of baseline noise, we investigated the effect on sinterability, grain size, grain boundary layer, etc. We selected various additives and investigated the relationship between their additive amounts and baseline noise occurrence. Furthermore, by analyzing the grain boundary layer and its vicinity, we found the following solution.

That is, the present invention comprises a pair of magnetic cores that are made of Mn-Zn polycrystalline ferrite, have a magnetic gap on their abutting surfaces, and constitute a main magnetic circuit, and an abutment between at least one of the magnetic cores. A metal magnetic thin film formed on the mating surface in contact with the magnetic gap and constituting an auxiliary magnetic circuit, and an excitation coil wound around the affected part of the magnetic core, the track width being 16 μm or less. In a narrow-track monolithic floating magnetic head, the Mn-Zn polycrystalline ferrite constituting the magnetic core contains a subcomponent in weight percent relative to the main component (MnOyZnOsFexOs). ZrO as, and l or Nb
0.01 to 0.2 wt% 2O5 (ZrO8 and Nb2O
If two types of 5 are included, the total is 0.01 to 0.2
By adding (wt%), the present invention provides a floating magnetic head characterized in that the baseline noise of the reproduced output waveform is small and the waveform form is good.

Furthermore, in the magnetic head of the present invention, the width of the grain boundary layer between the crystal grains of the Mn-Zn polycrystalline ferrite is 100 Å or less, and the Mn-Zn polycrystalline ferrite is Under etching conditions with a surface roughness o of 1 to 1.25 μm measured in It is characterized by low baseline noise and good waveform form.

(Function) In the grain boundary layer of polycrystalline ferrite, among the impurities contained in the raw materials and trace components added during the manufacturing process, components that are difficult to dissolve in the ferrite crystal grains remain, forming a thin boundary layer. It was formed.

The grain boundary layer may be amorphous, or the grain boundary layer and the vicinity of the grain boundary layer of crystal grains may be nonmagnetic because nonmagnetic ions such as Ca*Z si← are likely to segregate.

Magnetic properties have deteriorated.

In addition, since crystal grains have a chemical composition, stress is generated in the vicinity including the grain boundary layer due to the difference in thermal expansion coefficient.
It is thought that an easy-to-etch region is formed that is more easily etched than the inside of the crystal grain.

However, even in such grain boundary layers and easily etched areas with poor magnetic properties, it is possible to reduce the spacing of non-magnetic ions such as Ca''+ and Si4+, and to reduce the width to less than 100 Å or 1 μm.
It is considered that by making the number m or less, the degree of influence on the reproduced waveform can be weakened.

The reason for limiting the content of the subcomponents added to the Mn-Zn polycrystalline ferrite is as follows.

The purpose of adding ZrO and Nb2O5 is to add CaO and Si
It suppresses impurities such as O from being segregated into the grain boundary layer and near the grain boundary layer of crystal grains, but 0.01wt
% or less, there is no effect, and even if the content is 0.2 wt% or more, the effect remains the same.On the contrary, in order to make precipitation of different phases more likely to occur, the content is set in the range of 0.01 to 0.2 wt%.

By the way, in Japanese Patent Application Laid-open No. 64-4905, ZrO,
0. A magnetic head is described in which a Mn-Zn polycrystalline ferrite doped with 2.2 wt% of O2N is used as a magnetic herad core, and a metal magnetic thin film is formed in the gap between the ferrite cores. The main purpose is to reduce the shedding of crystal grains on the sliding surface of the ferrite tape, and even though the configuration of the magnetic head is similar, its effect and
The effect is different from the present invention.

Furthermore, in JP-A No. 2-44098, ZrO
An example of a polycrystalline ferrite containing 0.005 to 0.5 wt of , is disclosed, and the purpose thereof is to increase magnetic permeability in a high frequency region of 5 to 10 MHz.

Furthermore, in Japanese Patent Application Laid-open No. 58-60629, Cao, V.
By adding 2O5 and Sin, the grain boundary width is increased from 50 to 150.
A spinel-type ferrite has been disclosed that is controlled by humans, has improved workability, and reduces chipping and cracking during polishing.

However, the invention described in the above publication is also limited to its structure,
They have different actions and effects.

(Example) "Example 1" Main components (Fe2O5: 53.5moQ%, Zn○: 1
5.5moj2%, MnO: 31. Omon%), ZrO,, Nb2O5, MgO, 5r as subcomponents
CO,, Gd, OII Y2O5, Tag, Mo0. ,
Only one of In2O5 and Gem was added to 0.
Added to contain 1wt%, mixed in a ball mill,
In order to improve the sinterability in the primary sintering, calcination was performed at a temperature of 980-1100℃ under a nitrogen atmosphere so that the spinelization rate of the calcined powder after calcination was 40-80%. I did it. After that, one-blow sintering was performed at 1250℃, and then further sintered at 1200℃.
, hot isostatic pressing was performed at 1000 atm and M n
A sintered body of Zn ferrite was obtained.

Table 1 shows the results of evaluating these Mn-Zn ferrite sintered bodies in terms of sinterability and crystal grain size.

Z r 011 N I)i0s+ Gd1os+ Y
A sintered body in which only one type of sOs was added at 0.1 wt% each could be sufficiently used as a magnetic head.

Table 1 “Example 2” Subcomponent (7) Z r Oat N bj○,, Gd2
By adding O5, Y, 0, a block of Mn-Zn polycrystalline ferrite, which showed good sinterability and appropriate crystal grain size, was processed to a predetermined size to form a C-type core and an I-type core. A metal magnetic thin film of Fe-AQ-5i with a thickness of approximately 2 μm was formed on the abutting surface of the C-type core and the type-1 core.Then, the C-type core and the type-1 core were bonded together. By bonding with glass, grinding and polishing to the specified dimensions, the track width is 12 μm, the gap length is 0.6 μm,
A monolithic floating magnetic head with a gap depth of 8 μm was fabricated.

A coil was wound around this magnetic head, and the influence of the added subcomponents on the baseline noise of the reproduced waveform was investigated using a 3.5-inch magnetic recording device.

The magnetic disk at this time was a sputter disk with an Hc of 1200 (Oe), a rotation speed of 3600 pμm, and a flying height of 0.19 μm.

Table 2 shows the results, with Z as a subcomponent.
It was found that when rO or Nb2O5 was added in an amount of 1 wt% O, a good floating magnetic head with reduced baseline noise of the reproduced waveform could be obtained.

Table 2 "Example 3" According to Example 2, ZrO, N as a subcomponent was found to reduce the baseline noise of the reproduced output waveform.
In order to confirm the suitable addition contents of b and ○, main components having the same composition as in Example 1 (Fe2O5, ZnO, Mn0
), ZrO and/or Nb as a subcomponent,
A Mn-Zn polycrystalline ferrite was prepared in the same manner as in Example 1, and a floating magnetic head was manufactured in the same manner as in Example 2. .

For these magnetic heads, we investigated their sintering properties and the noise of reproduced waveforms. The investigation method was the same as in Example 2.

The results are shown in Table 3.

Those that do not contain ZrO or Nb2O5 are:
The reproduced waveform noise cannot be reduced, probably because impurities such as CaO and Sin are highly concentrated in the grain boundary layer and its vicinity.

If more than 0.2 wt% of ZrO or Nb2O5 was added, foreign phases would precipitate, making it impossible to use as a magnetic head. ZrO, or Nb, 0. 0.01
When added in a range of 0.2 wt%, a good magnetic head without reproduction noise could be obtained.

Table 3 "Example 4" Next, the width of the grain boundary layer of Mn--Zn polycrystalline ferrite and the width of the easy-to-etch region on baseline noise were investigated.

The width of the grain boundary layer of Mn-Zn ferrite was measured by polishing a sintered block to several tens of OA and observing the grain boundary layer with a transmission electron microscope. The easily etched area was determined by mirror-finishing a sintered block, immersing it in a 50% HCQ solution at 80'C for 1 minute, observing the etched sample surface with a scanning electron microscope, and measuring its width. Further, at the same time, the surface roughness of the etched surface of the sample piece was measured using a stylus type roughness meter, and the surface roughness was in the range of 0.1 to 1.25 μm.

Table 4 shows the relationship between grain boundary layer width and reproduced waveform noise.
The relationship between the table-etching easy area and reproduced waveform noise is shown.

The width of the grain boundary layer is less than 100 Å, and the width of the easy etching area is 1 μ.
It has been found that a floating magnetic head whose core is made of Mn-Zn ferrite having a particle diameter of less than m has a small reproduced waveform noise and is good.

Table 4 Table 5 (Effects of the Invention) The present invention provides a monolithic floating magnetic head in which the main magnetic circuit is made of Mn-Zn polycrystalline ferrite and the auxiliary magnetic circuit is made of a metal magnetic thin film. By investigating the cause of the baseline noise of the reproduced waveform and adding sub-components of Zr01 and Nb2O5 to the main component of Mn-Zn polycrystalline ferrite, and adjusting the content to a suitable value, By appropriately controlling the width of the grain boundary layer of polycrystalline ferrite, the coercive force of magnetic recording media has been increased to cope with higher density recording, and the magnetic head itself has become particularly narrower. Also in recording devices, it has become possible to provide a floating magnetic head with good recording and reproducing characteristics.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view showing the configuration of a monolithic floating magnetic head, FIG. 1(b) is a perspective view of the main part of the magnetic gap, and FIG. 2(a) is a reproduction waveform of pseudo gap noise. FIG. 5B is a diagram showing baseline noise. Further, FIG. 3 is a diagram showing the relationship between track width and relative margin. 1, magnetic head 3, winding window 5, C-shaped core 7, reinforcing glass G, gap GΩ, gap length 2, slider 4, metal magnetic thin film 6, I-shaped core Tw. Track width Figure 1 (α) Figure 1 (b) Figure (cL) Figure (b) m-→Time diagram Track IFm (7LJ7rL)

Claims (3)

[Claims] (1) A pair of magnetic cores made of Mn-Zn polycrystalline ferrite and having a magnetic gap on their abutting surfaces and constituting the main magnetic circuit; A narrow track with a track width of 16 μm or less, comprising a metal magnetic thin film formed in contact with the magnetic gap and constituting an auxiliary magnetic circuit, and an excitation coil wound around the window of the magnetic core. In the monolithic floating type magnetic head, the Mn-Zn polycrystalline ferrite constituting the magnetic core has a main component (Mn
O, ZnO, Fe_2O_3), ZrO_2 and/or Nb_2O_5 as subcomponents in weight percent was added to 0.
01~0.2wt% (2 of ZrO_2 and Nb_2O_5
If it contains different types, the total amount is 0.01-0.2wt%
), the floating magnetic head is characterized by low baseline noise and good waveform form in the reproduced output waveform. (2) A pair of magnetic cores made of Mn-Zn polycrystalline ferrite and having a magnetic gap on their abutting surfaces and constituting the main magnetic circuit; A narrow track with a track width of 16 μm or less, comprising a metal magnetic thin film formed in contact with the magnetic gap and constituting an auxiliary magnetic circuit, and an excitation coil wound around the window of the magnetic core. In the monolithic floating type magnetic head, the Mn-Zn polycrystalline ferrite constituting the magnetic core has a main component (Mn
O, ZnO, Fe_2O_3), ZrO_2 and/or Nb_2O_5 as subcomponents in weight percent was added to 0.
01~0.2wt% (2 of ZrO_2 and Nb_2O_5
If it contains different types, the total amount is 0.01-0.2wt%
), the thickness of the grain boundary layer between the crystal grains is 100 Å or less, the baseline noise of the reproduced output waveform is small, and the waveform shape is good. (3) The Mn-Zn polycrystalline ferrite has a grain boundary layer and the vicinity of the grain boundary layer of polycrystalline grains under etching conditions with a surface roughness of 0.1 to 1.25 μm measured with a stylus roughness meter. 3. The floating magnetic head according to claim 1, wherein the width of the easy-to-etch area along the part is 1 μm or less, the baseline noise of the reproduced output waveform is small, and the waveform shape is good.