Dynamic magnetic information storage or retrieval – Head – Hall effect
Patent
1984-07-03
1987-05-05
Wolff, John H.
Dynamic magnetic information storage or retrieval
Head
Hall effect
338 32R, 324252, 360110, 360124, 360125, G11B 5127, G11B 533
Patent
active
046636838
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head employed for reproduction of signal magnetization on a magnetic recording medium such as a magnetic tape or the like.
2. Prior Art
The thin film magnetic head (referred to merely as the MR head hereinafter) employing the magnetoresistance effect (referred to merely as MR effect) of a ferromagnetic thin film is suitable for a reproducing head of PCM signals, etc. owing to the facts that its reproducing output does not depend on the relative speed with respect to the recording medium, and that the output thereof is comparatively large. However, for actual use, the thin film magnetic head as described above must be set, in its functioning point, at a place where the linearity thereof is as favorable as possible, since the relation between the external magnetic field and its resistance is non-linear.
Incidentally, in the MR head as described above, shield layers of a high permeability material are disposed at opposite sides of the ferromagnetic thin film for improving a resolution with respect to the signal magnetic field, and therefore, a bias impressing means for effectively applying a bias magnetic field to the ferromagnetic thin film is disposed within the shield layers.
For applying such a bias magnetic field, there has been considered a method for providing a hard magnetic film in the vicinity of the ferromagnetic thin film and a method in which electric current is caused to flow through an electrically conductive film disposed close to the ferromagnetic thin film. However, the former method has a problem related to demagnetization of the recording medium by the hard magnetic film used for the biasing. Meanwhile, the latter practice has such a disadvantage that in the case of a narrow gap head, distortion tends to be large, since the bias current cannot be caused to flow up to the optimum point due to a limitation in the current capacity of the film, and if a push-pull construction is employed for reduction of the distortion, azimuth accuracy of a very high degree is required, thus presenting a difficulty for actual applications from the viewpoint of interchangeability. Moreover, when the bias means as described earlier is disposed in the gap between the ferromagnetic film and the shield layers, this presents an obstruction in the case where the gap length is shortened, and thus, production of the MR head as a short wavelength reproducing head is made difficult.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a narrow gap thin film magnetic head which is capable of reproducing short wavelengths with less distortion, by setting the functioning point of a ferromagnetic thin film at the optimum value, without providing within the gap a bias means which may present a limitation in the reduction of gap length.
In accomplishing the above object, according to the present invention, there is provided an MR head which includes a ferromagnetic thin film having grating on at least one surface for displaying an MR effect, with angles formed between the direction of the grating and electric current flowing through said thin film being set to be larger than 60.degree. and smaller than 80.degree., means for causing electric current to flow through said ferromagnetic thin film, high permeability members disposed at opposite sides of said ferromagnetic thin film, and a non-magnetic insulating member disposed between said ferromagnetic thin film and said high permeability members.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram explanatory of a principle of functioning of an MR head,
FIG. 2 is a graph explanatory of a state of magnetic flux distribution within a ferromagnetic thin film,
FIG. 3 is a side sectional view of an MR head according to a first preferred embodiment of the present invention,
FIG. 4 is a diagram showing a ferromagnetic thin film portion of the MR head according to the first embodiment of the present invention,
FIG. 5 is a diagram showing the relat
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IBM Tech. Discl. Bull., vol. 20, No. 6, Nov. 77, pp. 2441-2442, "Initializing . . . Magnetoresistive Sensors" by Ferg.
Kaminaka Nobuyuki
Mitani Satoru
Youda Hiroshi
Garcia Alfonso
Matsushita Electric - Industrial Co., Ltd.
Wolff John H.
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