Method for producing magnetic heads
AssigneeDigital Equipment Corporation
InventorMichael L. Mallary
Life of this patent
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Abstract
The present technique involves the procedure of depositing magnetic material onto a substrate while subjecting the magnetic material, as it is deposited onto the substrate, to a magnetic bias field whose Oersted value is sufficient to substantially saturate the surface of the magnetic material in order to induce a state of uniaxial anisotropy.
Claims6
A process for fabricating a yoke member with a magnetic flux conducting path for a high frequency switching magnetic read head comprising the steps of:
- (a) forming a mask means on a suitable electricity conducting base;
- (b) electroplating a layer of magnetic flux permeable material through said mask means onto said electricity conducting base;
- and
- (c) subjecting said layer of magnetic flux permeable material, during said electroplating step, to a biasing magnetic flux field having a value which is not less than H.sub.demag /4 where H.sub.demag is determined by the following equation:
- H.sub.demag =Ms(90.degree.+TAN.sup.-1 (T/W))/360.degree.
- where:
- H.sub.demag =The demagnetizing field at the corner in Oersteds when the structure is completely saturated in the width direction,
- Ms=Average saturation flux density in gauss (10,000 gauss for permalloy with no gaps),
- T=Maximun structure thickness obtained during plating (in microns),
- W=The pole structure width (in microns),
- TAN.sup.-1 =Inverse tangent function in degrees,
- (d) forming said electricity conducting base with said electroplated layer of magnetic flux permeable material thereon into a yoke member to be used as part of said high frequency switching magnetic read head.
A yoke device to be part of a high frequency switching magnetic read head wherein said magnetic read head is designed to read in excess of 1500 tracks per inch comprising in combination:
- non-magnetic flux permeable substrate means formed to have a pole section whose width is in the 5 to 10 micron range;
- a layer of magnetic flux permeable material means secured by electrodeposition to a face of said substrate;
- said flux permeable material means being subjected to a biasing magnetic flux during electrodeposition having a value of not less than H.sub.dmag/ 4 where H.sub.dmag is defined by:
- H.sub.dmag =Ms(90.degree.+TAN.sup.-1 (T/W))/360.degree.
- where:
- H.sub.demag =The demagnetizing field at the corner in Oersteds when the structure is completely saturated in the width direction,
- Ms=Average saturation flux density in gauss (10,000 gauss for permalloy with no gaps),
- T=Maximum structure thickness obtained during plating (in microns),
- W=The pole structure width (in microns),
- TAN.sup.-1 =Inverse tangent function in degress so that the surface is substantially in a state of magnetic saturation so as to induce an easy axis parallel to said width of said pole piece.
Dependencies are inferred from the claim text.