US 5,703,740 A · Toroidal thin film head

Abstract

A low-noise toroidal thin film head ("TFH") device has low coil resistance and inductance, especially suitable for very high magnetic recording areal densities and channel frequencies. The length of a toroidal coil turn is only about 20-30% that of the length of an average turn in the conventional planar spiral coil design. This allows either reduction of the device thermal noise (by about 6 dB) and/or increase of the device operational frequency bandwidth (by a factor of 3-5). The toroidal coil coupling efficiency between each turn and the magnetic core is practically 100%, thereby improving the write and read-back efficiencies. In one embodiment a non-via large back-closure contact area is provided between the bottom and top magnetic poles along their entire back-side width, and all other open branches and loose ends in the magnetic circuit are eliminated. The magnetic core has a gradual, smooth toroidal (or a horse-shoe) shape with no loose ends, nooks, crevices, or sharp corners. The larger back-closure contact area decreases the magnetic core reluctance and improves the device efficiency. Utilization of a soft non-magnetic seed-layer, such as gold, eliminates interference noise due to the conventional magnetic (NiFe) seed-layer. Slight mechanical texturing (scratching) of the seed-layer along the intended easy axis helps to define and induce strong magnetic uniaxial anisotropy in the plated magnetic poles. All these features facilitate significant reduction of Barkhausen and other sources of device noise. Embodiments include conventional TFH's, Planar TFH's, Pinched-Gap TFH's, and various versions of Magnetoresistive (MR) TFH's.

Claims51

Dependent claims

A toroidal thin film head (TFH) device comprising:

a substrate;
a bottom magnetic pole disposed on said substrate and including a bottom yoke-arm and a bottom pole-tip portion, said bottom yoke-arm having an elongated first back portion of a predetermined length and width, and a transitioning front portion, said first back portion having a first back-end;
a non-magnetic gap layer formed over at least said bottom pole-tip of said bottom magnetic pole;
a top magnetic pole disposed over said gap layer and overlaying said bottom magnetic pole, said top magnetic pole including a top yoke-arm of substantially the same shape and dimensions as said bottom yoke-arm and a top pole-tip portion, said top yoke-arm having an elongated second back portion of a predetermined length and width, and a transitioning front portion, said second back portion having a second back-end;
said first back portion of said bottom yoke-arm and said second back portion of said top yoke-arm being magnetically connected to each other at a back-closure region extending along substantially the entire width of said first and second back-ends such that said bottom magnetic pole and said top magnetic pole combine to form a magnetic core;
and
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic poles, for each of said at least one magnetic pole said solenoid coil winding comprising:
a first set of electrically conductive strips disposed below, and being insulated from, said magnetic pole;
a second set of electrically conductive strips disposed above, and being insulated from, said magnetic pole;
and
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic pole in a manner to form a solenoid coil wrapped around said magnetic pole.

8 more elements

A planar toroidal thin film head (TFH) magnetic transducing device comprising:

a substrate having a major flat surface;
a bottom magnetic layer segment positioned over said major flat surface of said substrate, said bottom magnetic layer segment having essentially a constant width and a length determined by first and second opposing edges;
a top magnetic layer disposed above said bottom magnetic layer segment, said top magnetic layer having the same approximate overall length as said bottom magnetic layer segment, wherein said top magnetic layer comprises two separate pole-piece segments;
a magnetic transducing gap raised over an insulative pedestal, said transducing gap separating said pole-piece segments of said top magnetic layer;
each of said two magnetic pole-piece segments comprising a first portion and a second portion;
said first portion of each of said pole-piece segments comprising a narrow pole-tip region adjacent to said magnetic transducing gap and a tapered region wherein the width of said tapered region forms a transition from the width of said second portion to the width of the narrow pole tip region;
said second portion of each of said pole-piece segments having a substantially constant width, which is essentially equal to the width of said bottom magnetic layer segment;
each of said second portions of said pole-piece segments forms a magnetic closure with one of said opposing edges of said bottom magnetic segment;
wherein said bottom magnetic layer segment and said magnetic pole-piece segments of said top magnetic layer comprise a magnetic core;
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic segments of said magnetic core, said toroidal solenoid coil winding comprising:
a first set and a second set of electrically conductive strips;
said first set of electrically conductive strips being disposed below, and being insulated from, said magnetic segment of said magnetic core;
said second set of electrically conductive strips being disposed above, and being insulated from, said magnetic segment of said magnetic core;
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic segment of said magnetic core in a manner such as to form a toroidal coil wrapped around said magnetic segment of said magnetic core.

11 more elements

A planar toroidal thin film head (TFH) magnetic transducing device comprising:

a substrate having a major flat surface;
a bottom magnetic segment positioned over said major flat surface of said substrate, said bottom magnetic segment having essentially a constant width and a length determined by first and second opposing edges;
two magnetic pillars, each pillar having a top side, a bottom side, and a width essentially equal to the width of said bottom magnetic segment, wherein each of said magnetic pillars is disposed so as to rise above said bottom magnetic segment and wherein said bottom side of each of said magnetic pillars forms a bottom magnetic closure with one of said opposing edges of said bottom magnetic segment;
a top magnetic layer disposed above said bottom magnetic segment and said magnetic pillars, wherein said top magnetic layer comprises two pole-piece segments, each of said two magnetic pole-piece segments comprising a first portion and a second portion;
a magnetic transducing gap formed over an insulative pedestal, said magnetic transducing gap separating said two pole-piece segments of said top magnetic layer;
said first portion of each of said pole-piece segments comprises a pole-tip region adjacent to said magnetic transducing gap and a tapered region wherein the width of said tapered region forms a transition from said second portion to said pole tip region;
said second portion of each of said pole-piece segments having a substantially constant width, which is essentially equal to the width of said bottom magnetic layer segment;
each of said pole-piece segments forms an upper magnetic closure with the top side of one of said magnetic pillars;
a magnetic core comprising said bottom magnetic layer segment, said magnetic pillars, and said magnetic pole-piece segments of said top magnetic layer;
a toroidal solenoid coil winding comprising at least one turn wrapped around at least one of said magnetic segments of said magnetic core;
for each of said at least one magnetic segment said toroidal solenoid coil winding comprises a first set and a second set of electrically conductive strips;
said first set of electrically conductive strips being disposed below, and being insulated from, said magnetic segment of said magnetic core;
said second set of electrically conductive strips being disposed above, and being insulated from, said magnetic segment of said magnetic core;
said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said magnetic segment of said magnetic core in a manner such as to form a solenoid coil wrapped around said magnetic segment of said magnetic core.

11 more elements

Dependencies are inferred from the claim text.

Toroidal thin film head

Life of this patent

Toroidal thin film head

Life of this patent

Abstract

Claims51