Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1996-08-15
2001-05-15
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06233126
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a magnetic head having a head face and a thin-film structure, with a magnetoresistive element and a flux-guiding element of a magnetically permeable material having a relatively high relative magnetic permeability, a peripheral area of the magnetoresistive element extending opposite the flux-guiding element and an electrically insulating intermediate layer being present at least between the peripheral area and the flux-guiding element.
A magnetic head of this type is known from U.S. Pat. No. 4,425,593 (PHN 9357, herewith incorporated by reference). The known magnetic head is a read head which is used for detecting information-representing magnetic fields on a magnetic recording medium moving with respect to the magnetic head, particularly a magnetic tape. The magnetic head has a head face and comprises a substrate of a ferrite which constitutes a magnetic yoke, together with two aligned layer-shaped flux guides of a material having a relatively high relative magnetic permeability, for example, a nickel-iron alloy whose relative magnetic permeability is typically 1000. The magnetic head also comprises an elongate layer-shaped magnetoresistive element (MR element) provided with equipotential strips which has contact faces at two opposite ends and has such a magnetic anisotropy that the easy axis of magnetization at least substantially coincides with its longitudinal axis. The MR element is arranged within the magnetic yoke in such a way that a gap, which is present between the flux guides, is bridged by the MR element. The flux guides have facing end portions which are present opposite peripheral areas of the MR element extending parallel to the head face. An insulation layer of quartz extends both between the ferrite substrate and the electrically conducting MR element and between the MR element and the electrically conducting flux guides. Consequently, the known magnetic head incorporates a non-magnetic, electrically insulating material in the overlap areas constituted by the peripheral areas of the MR element and the facing end portions of the flux guides.
A drawback of the known magnetic head is that, due to the distance caused by the non-magnetic material between the peripheral areas of the MR element and the facing end portions of the flux guides, only a small portion of the magnetic flux originating from the magnetic recording medium is actually passed through the MR element during operation. In other words, the known magnetic head has a low efficiency.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a magnetic head of the kind described in the opening paragraph having an improved efficiency.
To this end, the magnetic head according to the invention is characterized in that the intermediate layer is magnetically permeable and has a relative magnetic permeability &mgr;
r
which complies with the condition: 1.1<&mgr;
r
<25. In the magnetic head according to the invention an intermediate layer having a relatively low relative magnetic permeability is used between the MR element and the flux-guiding element. It has surprisingly been found that such an intermediate layer yields a considerable increase of the magnetic flux between the MR element and the flux-guiding element when a magnetic medium is being read, and consequently has an essentially improved efficiency. The intermediate layer is preferably in direct contact with the magnetoresistive element as well as the flux-guiding element. It has even been found that an intermediate layer having a permeability of between 2 and 10 results in a surprisingly high efficiency.
The magnetic head according to the invention further has a technological advantage. It is relatively simple to form the intermediate layer having a relative permeability of between 1.1 and 25, while known deposition methods such as sputtering, MO-CVD or laser ablation are applicable. An oxidic soft-magnetic material such as a ferrite, for example MnZn ferrite, NiZn ferrite, LiZn ferrite, MgMnZn ferrite or a garnet, for example Co/Si doped YIG (Y
3
Fe
5
O
12
) is preferably used for forming the intermediate layer. It has been found that the intermediate layer has the required relative permeability already at a thin layer thickness. The layer thickness d is preferably between 0.1 and 1.0 &mgr;m.
It is to be noted that U.S. Pat. No. 4,754,354 (herewith incorporated by reference) proposes to provide a magnetic guide having a relatively high relative magnetic permeability as an intermediate layer between an MR element and a magnetically permeable yoke portion. A drawback of the measure proposed in U.S. Pat. No. 4,754,354 is its very difficult realisation. From a technological point of view, it is not easy to form thin layers having a relatively high relative magnetic permeability, because the desired stoichiometry is difficult to realise in the microstructure to be formed. U.S. Pat. No. 4,754,354 describes as a sole example an Fe
3
O
4
layer as a magnetic guide which is formed by means of the special techniques described in U.S. Pat. No. 4,477,319 (herewith incorporated by reference).
At least substantially the same effect can be achieved with the magnetic head according to the invention as with the magnetic head known from U.S. Pat. No. 4,754,354. However, the magnetic head according to the invention can be realised in a considerably simpler way than this known magnetic head.
It is an other object of the invention to improve the efficiency of the magnetic head described in the opening paragraph in a simple manner. Therefore, the invention also relates to a method of manufacturing a magnetic head having a head face and a thin-film structure, with a magnetoresistive element and a flux-guiding element having a relatively high relative magnetic permeability, in which a peripheral area of the magnetoresistive element extends opposite the flux-guiding element and in which an electrically insulating intermediate layer is present at least between the peripheral area and the flux-guiding element.
The method according to the invention is characterized in that magnetic material is deposited until said electrically insulating layer has a relative magnetic permeability &mgr;
r
of between 1.1 and 25. The method according to the invention is an easily realisable method of manufacturing a magnetic head having a high efficiency.
A practical embodiment of the method according to the invention is characterized in that magnetic material is directly deposited on the flux-guiding element for forming the intermediate layer, whereafter the magnetoresistive element is provided on the layer formed.
REFERENCES:
patent: 4425593 (1984-01-01), Postma
patent: 4477319 (1984-10-01), Abe et al.
patent: 4754354 (1988-06-01), Jeffers
Ruigrok Jacobus J. M.
Van Der Zaag Pieter J.
Van Kampen Harald
Spain Norman N.
Tupper Robert S.
U.S. Philips Corporation
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