Low-noise toroidal thin film head with solenoidal coil

• US 6,195,232 B1
• Filed: 09/17/1997
• Issued: 02/27/2001
• Est. Priority Date: 08/24/1995
• Status: Expired due to Term

• Current Assignee: Rembrandt Data Storage, LP (Rembrandt IP Management, LLC)
• Original Assignee: Torohead, Inc.
• Inventors: Cohen, Uri
• Primary Examiner(s): KLIMOWICZ, WILLIAM JOSEPH
• Application Number:
  US08/931,988
• Time in Patent Office: 1,259 Days
• Field of Search: 360/123-127
• US Class Current: 360/123.38
• CPC Class Codes: G11B 5/17 Construction or disposition of windings
• CPC Class Codes: G11B 5/3113 for improving the magnetic domain structure or avoiding the formation or displacement of undesirable magnetic domains
• CPC Class Codes: G11B 5/3123 by using special coil configurations or conductors
• CPC Class Codes: G11B 5/313 Disposition of layers
• CPC Class Codes: G11B 5/3163 Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
• CPC Class Codes: G11B 5/3183 intersecting the gap plane, e.g. "horizontal head structure"
• CPC Class Codes: G11B 5/3967 Composite structural arrangements of transducers, e.g. inductive write and magnetoresistive read G11B5/3906 takes precedence

Abstract

The invention relates to a low-noise toroidal TFH device including a solenoidal or helical coil with low coil resistance and inductance, especially suitable for very high magnetic recording areal densities and channel frequencies. The length of a solenoidal coil turn is only about 20-30% that 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). Also, the solenoidal coil coupling efficiency between each turn and the magnetic core is practically 100%, thereby improving the write and read-back efficiencies. Other features of the invention include a non-via large back-closure contact area between the bottom and top magnetic poles along their entire back-side width, and elimination of all other open branches and loose ends in the magnetic circuit. 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.

Claims

1. A thin film head (TFH) magnetic transducing device comprising:

a substrate;

a bottom magnetic pole disposed over said substrate, said bottom magnetic pole comprising a bottom pole-tip portion and a bottom back portion, said bottom back portion comprising a bottom elongated region, said bottom elongated region having a bottom back-end;

a non-magnetic gap layer deposited over at least said bottom pole-tip portion of said bottom magnetic pole;

a top magnetic pole disposed over said gap layer and over said bottom magnetic pole, said top magnetic pole substantially overlying said bottom magnetic pole, said top magnetic pole comprising a top pole-tip portion and a top back portion, said top back portion comprising a top elongated region and a transitioning top front portion extending between said top elongated region and said top pole-tip portion, said top pole-tip portion having a width smaller than a width of said top elongated region, said top elongated region having a top back-end, said bottom back portion and said top back portion being magnetically connected to each other at a back-closure contact area, said back-closure contact area being located within a back-closure region, said back-closure contact area extending along substantially an entire width of at least one of said top and bottom back-ends, said width of said top elongated region being not larger than a width of said bottom elongated region, said pole-tip portions terminating at an air bearing surface, said width of said top pole-tip portion and each of said top and bottom elongated regions being measured in a direction perpendicular to a magnetic flux direction therein during write operations, said width in each instance being parallel to said air bearing surface; and

one or more of (a) a bottom solenoidal coil, comprising at least one turn, wrapped around said bottom magnetic pole and (b) a top solenoidal coil, comprising at least one turn, wrapped around said top magnetic pole.

2. A TFH device as recited in claim 1, wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil comprising a first set of electrically conductive strips disposed below, and being insulated from, said bottom magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said bottom magnetic pole;

said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said bottom magnetic pole in a manner to form a solenoidal coil wrapped around said bottom magnetic pole; and

(b) a top solenoidal coil comprising a first set of electrically conductive strips disposed below, and being insulated from said top magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said top magnetic pole;

said first set of electrically conductive strips and said second set of electrically conductive strips being joined along the sides of said top magnetic pole in a manner to form a solenoidal coil wrapped around said top magnetic pole.

3. A TFH device as recited in claim 2 wherein said one or more or (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises a bottom solenoidal coil wrapped around at least a portion of said bottom magnetic pole and a top solenoidal coil wrapped around at least a portion of said top magnetic pole.

4. A TFH device as recited in claim 3 wherein said top and bottom solenoidal coils have an equal number of turns.

5. A TFH device as recited in claim 3 wherein said top and bottom solenoidal coils have an unequal number of turns.

6. A TFH device as recited in claim 3 wherein at least one of said bottom solenoidal coil and top solenoidal coil has an axis which is substantially perpendicular to said air bearing surface.

7. A TFH device as recited in claim 2 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil comprising;

a first set of electrically conductive strips disposed below, and being insulated from, said bottom magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said bottom magnetic pole;

bottom contact pads configured along the sides of said bottom magnetic pole; and

(b) a top solenoidal coil comprising a first set of electrically conductive strips disposed below, and being insulated from, said top magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said top magnetic pole; and

top contact pads configured along the sides of said top magnetic pole.

8. A TFH device as recited in claim 7 wherein one or more of said (a) bottom contact pads and (b) top contact pads comprises one or more of:

(a) bottom contact pads configured in a staggered manner along both sides of said bottom magnetic pole; and

(b) top contact pads configured in a staggered manner along both sides of said top magnetic pole.

9. A TFH device as recited in claim 7 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil comprising;

a first set of electrically conductive strips disposed below, and being insulated from, said bottom magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said bottom magnetic pole;

bottom contact pads configured along the sides of said bottom magnetic pole; and

at least one insulation layer which extends on at least one side of said bottom magnetic pole to within a short distance from said bottom contact pads; and

(b) a top solenoidal coil comprising a first set of electrically conductive strips disposed below, and being insulated from, said top magnetic pole;

a second set of electrically conductive strips disposed above, and being insulated from, said top magnetic pole;

top contact pads configured along the sides of said top magnetic pole; and

at least one insulation layer which extends on at least one side of said top magnetic pole to within a short distance from said top contact pads.

10. A TFH device as recited in claim 2 wherein at least one of said bottom magnetic pole and said top magnetic pole comprises electroplated magnetic layers.

11. A TFH device as recited in claim 2 further comprising a magnetoresistive (MR) read element.

12. A TFH device as recited in claim 11 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises said top solenoidal coil.

13. A TFH device as recited in claim 11 wherein said one or more of (a) a bottom solenoidal coil and (b) a top, solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil comprising at least a single turn; and

wrapped around said top magnetic pole.

14. A TFH device as recited in claim 1 wherein a top distance between said air bearing surface and said top back-end is greater than a bottom distance between said air bearing surface and said bottom back-end such that said top back portion is wrapped around said bottom back portion.

15. A TFH device as recited in claim 14 wherein a difference between said top distance and said bottom distance does not exceed the thickness of said top back portion.

16. A TFH device as recited in claim 1 wherein said back-closure region has a length, measured perpendicular to said air bearing surface, which is equal to or larger than the thickness of the thinner of said top and bottom back portions.

17. A TFH device as recited in claim 16 wherein the length of said back-closure region is in the range of 1.2-2.0 times the thickness of the thinner of said top and bottom back portions.

18. A TFH device as recited in claim 1 further comprising an insulation layer between said top and bottom magnetic poles, there being no via formed in said insulation layer in said back-closure region in order to connect said top and bottom magnetic poles.

19. A TFH device as recited in claim 1 wherein at least one of said bottom magnetic pole and said top magnetic pole comprises a magnetic material selected from the group consisting of NiFe, CoZr, CoNbZr, CoTaZr, FeSi, FeAlSi, FeN, FeAlN, FeTaN, CoFe, CoNiFe, and CoFeB.

20. A TFH device as recited in claim 19 wherein at least one of said bottom magnetic pole and said top magnetic pole comprises a laminated structure consisting of alternating magnetic and non-magnetic layers.

21. A TFH device as recited in claim 20 wherein said non-magnetic layers comprise non-magnetic electrically insulating layers.

22. A TFH devices as recited in claim 1 wherein at least one of said bottom magnetic pole and said top magnetic pole comprises NiFe alloy.

23. A TFH device as recited in claim 1 wherein a width of said bottom elongated region is substantially equal to a width of said top elongated region, measured in any plane parallel to said air bearing surface.

24. A TFH device as recited in claim 1 wherein a width of each of said bottom elongated region and said top elongated region is substantially constant at any distance from said air bearing surface.

25. A TFH device as recited in claim 24 wherein a ratio between the width and length of each of said top and bottom elongated regions, said length being measured in a direction perpendicular to said air bearing surface, is within the range of 0.4-0.7.

26. A TFH device as recited in claim 1 wherein at least one of said top and bottom elongated regions is tapered along its length.

27. A TFH device as recited in claim 1 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil being situated relative to said bottom magnetic pole in such a manner as to induce a magnetic flux parallel to a single hard axis direction, normal to said air bearing surface, substantially throughout said bottom magnetic pole during write operations; and

(b) a top solenoidal coil being situated relative to said top magnetic pole in such a manner as to induce a magnetic flux parallel to a single hard axis direction, normal to said air bearing surface, substantially throughout said top magnetic pole during write operations.

28. A TFH device as recited in claim 27 wherein at least one of said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises an electrically conductive metal selected from the group consisting of Cu, Au, Pd, Pt, Ag, and Al.

29. A TFH device as recited in claim 27 wherein at least one of said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises an electrically conductive metal selected from the group consisting of Cu, Au, and Al.

30. A TFH device as recited in claim 1 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises one or more of:

(a) a bottom solenoidal coil being closely wrapped around said bottom magnetic pole along substantially the entire distance between an onset point of said bottom back portion and said back-closure region; and

(b) a top solenoidal coil being closely wrapped around said top magnetic pole along substantially the entire distance between an onset point of said top back portion and said back-closure region.

31. A TFH device as recited in claim 1 wherein at least one of said bottom magnetic pole and said top magnetic pole comprises sputter deposited or evaporation-deposited layers.

32. A TFH device as recited in claim 1 wherein neither of said bottom magnetic pole and said top magnetic pole comprises a wing portion.

33. A TFH device as recited in claim 1 wherein said back-closure contact area extends along at least 90% of the width of at least one of said top and bottom back-ends.

34. A TFH device as recited in claim 1 wherein said back-closure contact area extends along at least 95% of the width of at least one of sa d top and bottom back-ends.

35. A TFH device as recited in claim 1 wherein said one or more of (a) a bottom solenoidal coil and (b) a top solenoidal coil comprises said top solenoidal coil, and wherein said bottom magnetic pole comprises a part of a magnetoresistive (MR) read device.

36. A TFH device as recited in claim 1 wherein said bottom and top magnetic poles are associated with only a single TFH transducing device.

37. A TFH device as recited in claim 1 wherein said top magnetic pole overlaps and is wrapped around said bottom back-end within said back-closure region.

38. A thin film head (TFH) magnetic transducing device comprising:

a substrate;

a bottom magnetic pole formed over said substrate, said bottom magnetic pole having a predetermined width and length, said length extending between a first end and a second end of said bottom magnetic pole;

a top magnetic pole formed over, and substantially overlying, said bottom magnetic pole, said top magnetic pole being disposed substantially above said bottom magnetic pole, relative to said substrate, said top magnetic pole comprising a top pole-tip and a top back portion each having a predetermined width measured in a direction parallel to an air bearing surface, said width of said top pole-tip being smaller than said width of said top back portion, said top magnetic pole having a predetermined width and length, said length extending between a first end and a second end of said top magnetic pole, wherein said length of said top magnetic pole is larger than said length of said bottom magnetic pole, such that said top back portion is wrapped around said second end of said bottom magnetic pole, said second end of said top magnetic pole being connected to said second end of said bottom magnetic pole in a back-closure region; and

one or more of (a) a bottom solenoidal coil wrapped around said bottom magnetic pole and (b) a top solenoidal coil wrapped around said top magnetic pole;

wherein said first ends coincide with said air bearing surface, a transducing gap being formed between said first ends, and wherein said width of said top magnetic pole is no greater than said width of said bottom magnetic pole measured in any plane parallel to said air bearing surface.

39. A thin film head (TFH) magnetic transducing device comprising:

a substrate;

a bottom magnetic pole formed over said substrate, said bottom magnetic pole having a predetermined width and length, said length extending between a first end and a second end of said bottom magnetic pole;

a top magnetic pole formed over, and substantially overlying, said bottom magnetic pole, said top magnetic pole being disposed substantially above said bottom magnetic pole, relative to said substrate, said top magnetic pole comprising a top pole-tip and a top back portion each having a predetermined width measured in a direction parallel to an air bearing surface, said width of said top pole-tip being smaller than said width of said top back portion, said top magnetic pole having a predetermined width and length, said length extending between a first end and a second end of said top magnetic pole, wherein said top magnetic pole overlaps and is wrapped around said second end of said bottom magnetic pole, said second end of said top magnetic pole being connected to said second end of said bottom magnetic pole in a back-closure region; and

one or more of (a) a bottom solenoidal coil wrapped around said bottom magnetic pole and (b) a top solenoidal coil wrapped around said top magnetic pole;

wherein said first ends coincide with said air bearing surface, a transducing gap being formed between said first ends, and wherein said width of said top magnetic pole is no greater than said width of said bottom magnetic pole measured in any plane parallel to said air bearing surface.

40. A thin film head (TFH) magnetic transducing device comprising:

a substrate;

a bottom magnetic pole disposed over said substrate, said bottom magnetic pole comprising a bottom pole-tip portion and a bottom back portion, said bottom back portion terminating at a bottom back-end;

a non-magnetic gap layer deposited over at least said bottom pole-tip portion of said bottom magnetic pole;

a top magnetic pole disposed over said gap layer, said top magnetic pole comprising a top pole-tip, a top back portion and a top transition portion, said top back portion terminating at a top back-end, said bottom back portion and said top back portion being magnetically connected to each other at an area of contact within a back-closure region, said top and bottom pole-tips terminating at an air bearing surface;

a first solenoidal coil wrapped around said bottom magnetic pole; and

a second solenoidal coil wrapped around said top magnetic pole, said first and second solenoidal coils being connected in series, each of said first and second solenoidal coils comprises at least one bottom layer and at least one top layer of conductive strips, each of said first and second solenoidal coils includes contact pads for connecting successive coil layers, configured along sides of said bottom and top magnetic poles, respectively, wherein said contact pads are configured in a staggered manner along at least one side of each of said bottom and top magnetic poles;

wherein said bottom and top back portions have a substantially uniform width W₁ and said top pole-tip has a width W_2T, and W₁ is greater than W_2T, said top transition portion being tapered to accommodate the difference between W₁ and W_2T, said top magnetic pole being disposed substantially above said bottom magnetic pole, relative to said substrate, wherein said top magnetic pole substantially overlying said bottom magnetic pole in all regions, including at least a portion of said back-closure region, and wherein said area of contact also has a width substantially equal to W₁.