JPS61202388A - Magnetic double layer disk for buried servo system - Google Patents

Abstract

PURPOSE:To reduce the effect of the mixture of the servo signal into the data signal by a degree equivalent to a guard band, by securing such a constitution where a servo pattern of a servo magnetic layer having a guard band which contains no servo information between servo tracks. CONSTITUTION:A guard band containing no servo information between servo tracks of the lower servo magnetic layer of a magnetic double layer disk. Then a data track is set on the guard band of the servo track. Therefore the data signal receives substantially no effect of the mixture of the servo signal in case the data track width is smaller than the guard band width. Furthermore the effect of the mixture of the servo signal is reduced for the data signal by a degree equivalent to the guard band width of the servo track against the data track width in case the data track width is larger than the guard band width.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a track following servo system for a magnetic disk device, and more particularly to a magnetic double layer disk in a buried servo system.

(Prior art and its problems) Conventionally, the servo surface servo method has been the mainstream for magnetic disk drives, but in this servo surface servo method, the servo disk and data disk are placed on separate disk plates. However, there is a risk of errors in positioning accuracy due to differences in ambient temperature. In particular, this servo surface servo system has disadvantages such as the relative positioning error of the magnetic head increases as the track density increases, making it difficult to increase the track density and thus making it difficult to realize a high recording density.

In recent magnetic disk drives, various data surface servo systems are being considered to improve head positioning accuracy.
In particular, data surface servo systems include sector servo systems that use part of the data surface, systems that use the data information themselves, and systems that use a magnetic double layer disk with the lower magnetic film as the servo information medium and use that information (hereinafter referred to as buried servo systems). method) etc. are being considered.

The sector servo method divides one track into sectors and partially inserts servo information, but it has the drawback that track servo cannot be performed in areas other than the areas where servo information is input. Therefore, the positioning accuracy is insufficient at high track densities. Furthermore, the servo method that uses data information itself as servo information has the disadvantage that a fluctuation in the output envelope of data information causes a positioning error because the data information itself is used.

Furthermore, in the servo system that uses two layers of magnetic films, the upper layer is used for data information and the lower layer is used for servo information, and one data head simultaneously detects the data and servo information and separates them. positioning error is small due to the use of However, in the servo system using this magnetic double layer medium, one data head is used to detect data information and servo information at the same time, and a filter is used to separate the data information and servo information during playback. Although it is easy to perform, when recording, a filter or bias circuit is required in the recording circuit to detect the servo information, and it requires a complicated circuit configuration, which may degrade the servo information. However, it also has the disadvantage of increasing the cost of the circuit system. To solve this problem, as a thin-film magnetic head for buried servo method, a data transducer is placed on one of the two rails of the same slider, and a servo transducer is placed on the other rail. There is a method of separating them and preventing deterioration of S and H during recording.

In such a buried servo system, a two-frequency method has been proposed in which the servo pattern of the lower servo layer is divided into odd-numbered tracks and even-numbered tracks.

However, this buried servo system using a magnetic double-layer disk has the disadvantage that interference between the data signal and the servo signal, particularly harmonic components of the servo signal, affects the data signal.

(Object of the Invention) An object of the present invention is to improve the conventional problem that harmonic components of servo signals affect data signals and to provide a magnetic double-layer disk for six buried servo system.

(Structure of the Invention) The magnetic double layer disk for buried servo system of the present invention includes:
In a magnetic double layer disk for buried servo system having an upper magnetic layer for data and a lower magnetic layer for servo,
The servo pattern of the servo magnetic layer has a guard band between servo tracks in which no servo information exists.

(Detailed explanation of configuration FIA) The magnetic double layer disk for buried servo system of the present invention has a guard band (DC demagnetization or AC demagnetization) in which servo information does not exist between servo tracks of the servo magnetic layer (lower layer) of the magnetic double layer disk. It is characterized in that the data track (the position of the data transducer) is located above the guard band of the servo track.

Therefore, when the data track width (the track width of the data transducer) is less than or equal to the guard band width of the servo track, the data signal is hardly affected by the servo signal. Further, when the track width of the data track is larger than the guard band width of the servo track, the influence of the servo signal mixing on the data signal is reduced by the amount of the guard band width of the servo track with respect to the data track width.

Here, the magnetic double layer disk is Co-N1-P.

Plated disks using plating films such as Co-P, and y-
F@101, Co-doped 1Fe@O@, QrPt
Thin film disks using sputtered or vapor-deposited films such as , Co-Ni, coating disks coated with powder particles of y-Fe@O@, etc. are used, and as magnetic heads, crystalline NiFe, sendust, amorphous Co, etc. are used. -Zr,C
oZrNb.

Alloys such as CoTa, CoHf, or MnZn, NiZn
A configuration in which a servo transducer and a data transducer are mounted on the same rail on the same slider or on separate rails using bulk 7 elites such as The features of the present invention can be utilized in combination with the head.

(Example) Hereinafter, an example of a servo pattern for buried servo system according to the present invention will be described with reference to the drawings. FIG. 1 shows a buried system servo pattern according to an embodiment of the present invention, and FIG. b
) shows the relationship between data tracks and servo tracks as seen from a cross section of the magnetic double layer disk.

The magnetic double-layer disk for buried servo system is made by N4P plating on -AI alloy, and on a non-magnetic substrate 1 whose surface is polished, there is a magnetic layer 2 for servo (ferrite sputtered film) with a high coercive force (He"13000e). Film thickness 0.2μm
) was coated on the servo magnetic layer 2 by a sputtering method, and a non-magnetic layer 3 (Sin, film: film thickness: 0.2 μm) was coated on the servo magnetic layer 2 by a sputtering method. Data magnetic layer 4 (ferrite film: film thickness 0.15 μm, coercive force He'
A protective film 5 (sto, @: film thickness 0.02 μm) is coated on the data magnetic layer by sputtering.
). This magnetic double layer disk for buried servo system has a gap length of 5 μm and a servo track width of 15 μm (in this case, the data track pitch is 2 μm).
A magnetic double layer disk is fully DC demagnetized using an MnZn bulk ferrite head with a servo track width of 0 μm), and then the head with a servo track width of 15 μm is used with a data track pitch (
servo signal frequency fs, h-h every 20μm)
(3 frequencies) and the servo signals were recorded by changing the track order.

Therefore, in this state, the card band between the servo tracks is 5 μm. Then, using a data thin-film magnetic head with a gap length of 0.3 μm and a track width of 15 μm, the servo signals recorded on the data magnetic layer were completely DC demagnetized. Eleven of the bands were left with DC demagnetized form.

Using the magnetic double layer disk manufactured as described above and a thin film magnetic head for data with a track width of 15 μm and a gap length of 0.3 μm, the thin film magnetic head for data was fixed at the position of the guard band of the servo track, and the data signal was As a result of recording and reproducing the data and observing the amount of servo signal mixed in, it was reduced by the amount of the guard band.

(Effects of the Invention) As described above, according to the present invention, the influence of the servo signal mixed into the data signal can be reduced by the amount of the guard band. It goes without saying that the present invention can also be applied to combinations of magnetic double layer disks and magnetic heads other than those in this embodiment.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams showing the relationship between data tracks and servo tracks of a magnetic double layer disk according to an embodiment of the present invention. In Fig. 1 (at, (b)) 1 is a non-magnetic substrate, 2
is a magnetic layer for servo, 3 is a non-magnetic layer, 4 is a magnetic layer for data, 5 is a protective film, 6 is an n servo track, 7.9° 11
is servo track guard band, 8 is n+1 servo track, 10 is n+2 servo track, 12 is n+3
Servo track, 14 is m data track, 13.15
, 17.19 is the data track guard band, 16 is m
+1 data track and 18 indicate m+2 data track, respectively. Representative patent attorney Uchihara Y shift% 7

Claims (1)

[Claims] In a magnetic double layer disk for buried servo system having an upper magnetic layer for data and a lower magnetic layer for servo,
1. A magnetic double layer disk for buried servo system, characterized in that a servo pattern of a servo magnetic layer has a guard band in which servo information does not exist between servo tracks.