Thin film inductive transducer

• US 4,190,872 A
• Filed: 12/21/1978
• Issued: 02/26/1980
• Est. Priority Date: 12/21/1978
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Jones, Robert E. Jr., Nystrom, Walther
• Primary Examiner(s): Eddleman, Alfred H.
• Application Number:
  US05/972,104
• Time in Patent Office: 432 Days
• Field of Search: 360/125, 360/122, 360/119-120, 360/126-127
• US Class Current: 360/125.52
• CPC Class Codes: G11B 5/3116 Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks G11B5/3113, G11B5/245 take precedence
• CPC Class Codes: G11B 5/313 Disposition of layers

Abstract

This thin film inductive transducer comprises a yoke structure consisting of a pole tip region which joins a back region. To maximize resolution during reading of magnetic transitions from a moving magnetic recording medium, the pole tip region is of preselected constant relatively narrow width, and composed of magnetic layers having edges which extend in a direction normal to the medium for a distance D from an air bearing surface ABS to the back region and having a small thickness at least adjacent the ABS. To minimize the effects of spurious signals from adjacent tracks on the medium, distance D is at least 5/d, where d is the recording density on the medium; however, to maximize transducer efficiency, distance D is not increased significantly above 5/d. To oppose saturation of the yoke structure with applied current and enhance the efficiency of the transducer during recording, the cross-sectional area of the yoke structure is increased in the back region by progressively increasing its width rearward of the pole tip region and concurrently increasing the thickness of said magnetic layers at least about 60%.

Claims

1. A thin film inductive transducer for recording and reading magnetic transitions on a selectable one of a plurality of tracks on a magnetic recording medium, said transducer being of the type comprising two layers of a magnetic material forming a yoke structure that is activated by a conductor coil characterized in that:

said yoke structure adjacent its one end comprises a pole tip region in which the layers are of a predetermined substantially constant width and a preselected substantially constant thickness, said predetermined width not exceeding the width of a track on the medium, and said pole tip region extending from said one end a relatively short distance normal to the magnetic medium to an "optimum transition point", thereby to maximize resolution of transitions during recording; and

said yoke structure comprises a back region which joins said pole tip region at said "optimum transition point" and in which the layers increase progressively in width from said predetermined width, said back region having a back gap substantially centered adjacent its wider end, the thickness of the layers of magnetic material in said back region being greater than said preselected constant thickness of those layers in said pole tip region, thereby to oppose saturation of the yoke structure with applied current and enhance efficiency of the transducer by increasing the cross-sectional area of the yoke structure.

2. A transducer according to claim 1, further characterized in that the yoke structure as viewed in a direction transverse to the path of the magnetic medium has a configuration substantially similar to that of a ping-pong paddle in plan view.

3. A transducer according to claim 1, further characterized in that said distance is about 5/d, where d is the recording density on the medium.

4. A transducer according to claim 1, further characterized in that each of the layers of magnetic material in said pole tip region have a thickness t and in said back region have a thickness of the order of about at least 160%t.

5. A transducer according to claim 1, further characterized in that the back region increases progressively in width by diverging at a preselected angle of between about 30°

and 60°

from an axis of symmetry of the yoke structure.

6. A transducer according to claim 1, further characterized in that said relatively short distance is between 12 and 18 microns, when recording density on the medium is of the order of about 400 flux changes per millimeter.

7. A transducer according to claim 1, further characterized in that said pole tip region comprises:

a pole tip of relatively small total thickness extending a preselected small distance from said one end of the yoke structure to a "zero throat point", and

a pole tip extension in which the thickness of the layers remain substantially constant, but at least one of the layers diverges from said zero throat point to the "optimum transition point" at which the thickness of each layer increases to a larger dimension and the back region commences.

8. A transducer according to claim 7, wherein said preselected small distance does not exceed about 3 microns and the distance from the zero throat point to the optimum transition point is of the order of about 12 to 15 microns.

9. A thin film inductive transducer for recording and reading magnetic transitions on a magnetic recording medium, said transducer comprising;

two layers of a magnetic material deposited on a substrate and forming a yoke structure comprising a pole tip region and a back region;

non-magnetic material deposited between said two layers except at a back gap in the back region, said non-magnetic material forming a transducing gap at the pole tip region;

a flat conductor coil including a plurality of deposited substantially helical turns, at least respective one portions of which are disposed between the two layers of the yoke structure; and

insulating material electrically insulating each such portion of the conductor coil from the yoke structure;

said pole tip region being relatively narrow and disposed at the operational ends of said layers adjacent the magnetic medium and extending to an "optimum transition point" at which said back region joins and becomes progressively substantially wider than said pole tip region and the thickness of each of said layers increases to the order of about 160% of its thickness in said pole tip region;

said pole tip region remaining approximately the same width to said "optimum transition point" and for a distance from said operational ends which is about 5/d, where d is the recording density on the magnetic medium.

10. A thin film inductive transducer for recording and reading magnetic transitions on a track of a moving magnetic recording medium, said transducer comprising:

a first layer of a magnetic material deposited on a substrate in two stages to provide a deposit of reduced thickness in a pole tip region adjacent one end of what will become a yoke structure;

non-magnetic material deposited on said first layer except at a back gap adjacent the opposite end of what will become a back region of the yoke structure;

insulating material deposited on said non-magnetic layer except adjacent the pole tip region;

a conductor coil having generally helical turns, respective portions of which are deposited on said insulating material;

insulating material deposited on said coil turns; and

a second layer of magnetic material deposited over the last-mentioned insulating material and cooperating with said first layer to form the yoke structure in which said layers straddle and are insulated from said coil, said first layer being in physical contact with said second layer at the back gap;

said second layer being of reduced thickness adjacent its one end overlying said one end of said first layer to provide the pole tip region with a narrow width approximating that of the track of the medium, said pole tip region extending from proximity with the medium a distance approximately 5/d, where d is the recording density on the medium, said layers at said pole tip region being separated by said non-magnetic material to form a magnetic gap, and said layers in said back region being of increased thickness and diverging generally uniformly from said narrow width to a preselected greater width, terminating shortly beyond said back gap.