US3867368A - Read-write magnetic transducer having a composite structure comprising a stack of thin films - Google Patents

Read-write magnetic transducer having a composite structure comprising a stack of thin films Download PDF

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Publication number
US3867368A
US3867368A US409613A US40961373A US3867368A US 3867368 A US3867368 A US 3867368A US 409613 A US409613 A US 409613A US 40961373 A US40961373 A US 40961373A US 3867368 A US3867368 A US 3867368A
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United States
Prior art keywords
magnetic
read
write
pole
layer
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Expired - Lifetime
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US409613A
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English (en)
Inventor
Jean-Pierre Lazzari
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Compagnie Internationale pour lInformatique
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Cii
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
    • G11B5/3109—Details
    • G11B5/313—Disposition of layers
    • G11B5/3143—Disposition of layers including additional layers for improving the electromagnetic transducing properties of the basic structure, e.g. for flux coupling, guiding or shielding
    • G11B5/3146—Disposition of layers including additional layers for improving the electromagnetic transducing properties of the basic structure, e.g. for flux coupling, guiding or shielding magnetic layers
    • G11B5/3153—Disposition of layers including additional layers for improving the electromagnetic transducing properties of the basic structure, e.g. for flux coupling, guiding or shielding magnetic layers including at least one magnetic thin film coupled by interfacing to the basic magnetic thin film structure
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/187—Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features
    • G11B5/245—Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features comprising means for controlling the reluctance of the magnetic circuit in a head with single gap, for co-operation with one track
    • G11B5/2452—Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features comprising means for controlling the reluctance of the magnetic circuit in a head with single gap, for co-operation with one track where the dimensions of the effective gap are controlled

Definitions

  • Each pole-piece of a read-write magnetic transducer having a geometrical airgap defined by a pair of polepieces and wherein passes a part of a read-write flat winging comprises a first layer made of magnetically soft material adjacent tothe airgap and a second layer made of magnetically hard materialawith an intervening layer of a structure ensuring de-coupling of the magnetizations of the said soft and hard magnetic material layers.
  • the present invention concerns improvements in or relating to the read-write magnetic transducers made in layers wherein a flat coil winding is partially inserted between two magnetic flat pole-pieces defining a geometrical airgap therebetween.
  • the magnetic circuit of the pole-pieces carries the field which, for a writing operation, is generated by the coil winding and during a read-out operation, said circuit carries the field generated from the magnetization variations of a record carrier.
  • the efficiency of the transducer may be defined by the ratio of the magnetic flux crossed by the coil winding to the magnetic flux available at the airgap level: the reluctance of the magnetic material ought to be in such a condition as low as possible from the winding to the airgap and, for a fair definition of the read-out signal, the length of the airgap ought to be the minimum one.
  • the efficiency of the transducer is related to the ratio of the writing field to the writing electrical current and of the gradient of the magnetic field at the airgap level: the magnetic material ought to have a substantially zero remanent flux density and, on the other hand, a maximal value saturation flux density, together with a permeability value well above 50.
  • this aim is reached by providing between a magnetically soft inner layer and a magnetically hard outer layer of a polepice, an intervening layer of such a structure that it provides tic-coupling of the magnztizations of the said two layers.
  • FIG. 1 shows an exploded view of a magnetic transducer structure according to the invention and from LII which may be plainly derived any modification within the field and scope of the appended claims,
  • FIG. 2 shows a top view of the structure
  • FIGS. 3 and 4 show cross-section views along section lines a) and b) of FIG. 2, and,
  • FIG. 5 shows a partial cross-section view of enlarged scale, of an illustrative embodiment of one of the pole piece ofa transducer made in accordance to the invention.
  • the material of this layer may be cobalt or an iron-cobalt alloy or, preferably, pure iron which has a saturation flux density higher than that of cobalt or of the iron-cobalt alloys.
  • Iron can be evaporated at temperatures compatible with these of the general process of evaporation of the layers of the structure. The remanent induction of iron is quite small and practically negligible with respect of that of the hard material which will be later used in the structure.
  • the saturation fiux density of evaporated iron substantially equals 20,000 gauss whereas the corresponding parametric value is about 18,000 for cobalt.
  • the permeability of iron when evaporated in a thin layer or film at a substrate temperature of about 200 to 300 C. with a thickness of about twenty microns for instance, is from to 300.
  • the saturation field of the layer which can be considered as corresponding to the anisotropy field of a uniaxial layer for the purpose of the invention, may reach and even outpass 25 Oersteds for identical geometrical dimensions.
  • Such a layer 2 is coated with a layer 3 the structure of which will be hereinbelow defined.
  • a layer 4 of a magnetic material having, with respect to the material of the layer 2, a lower saturation flux density, an appreciably higher permeability and a value of anisotropy field appreciably lower than the saturation field value of the layer 2.
  • the material of the layer 4 is an iron-nickel alloy having a saturation field density of the order of 10,000 gauss, a permeability value from 5000 to 1000 and an anisotropy field value of about 7 Oersteds, when evaporated to a substantially identical thickness as the layer 2.
  • a flat coil winding 5 is formed over the above stack of layers which, together, constitute one of the polepieces of the magnetic circuit of the transducer.
  • a flat coil winding is made of a flat multi-turn helix of relatively insulated conductors.
  • the winding is applied by its front branch over the stack of layers 2 to 4 and directly applies on the substrate l by its lateral and rear branches of legs. Once formed, it is completely coated with an insulating film 9, FIG. 4 except its front face which is level to the airgap. In said front face at least one insulated conductor of the winding is bare.
  • the airgap faces of the layers 2 to 4 and of the winding 5 are level with an edge of the substrate 1.
  • the length L3 of said edge equels the length Ll of the layers 2 and 3 plus twice the width A of the winding legs.
  • the length L2 of the layer 4 is preferably made lower than L1.
  • the thickness of the winding at its airgap face defines a geometrical airgap for the transducer.
  • the stack 2-3-4 constitutes one of the pole-pieces of the magnetic circuit of the transducer and the second polepiece is formed over the winding and the stack in symmetrical relation to the first, i.e., a layer 6 of same material and geometry as the layer 4, a layer 7 of same structure and geometry as the layer 3 and the layer 8 of same material and geometry as layer 2.
  • small blocks such as shown at 11 in FIG. 4, may be formed in insulating non-magnetic material of same thickness as the layer 6 on either side of said layer over the front branch of the winding 5.
  • the composite layer 6-ll then provides a flat surface for deposition of the layers 7 and 8 at this location of the structure.
  • the layers 7 and 8 will reach the lateral edges of the layer 6 up to the level of the top surface of the winding airgap leg.
  • intervening layers 3 and 7 is such that they create a magnetostatic decoupling between the layers 2 and 4, respectively between the layers 6 and 8, so that the magnetizations of the layers 4 and 6 cannot be disturbed by the magnetization of the layers 2 and 8.
  • Layers 2 and 8 are made of magnetically hard material as apparent from the above whereas layers 4 and 6 are made of magnetically soft material and, for an efficient operation of the head comprised of said transducer structure, it is imperative that the magnetizations of the soft layers cannot be influenced by the magnetizations of the hard layers so that the soft layers may preserve their easy magnetization axis parallel to the breadth of the airgap.
  • the decoupling layers 3 and 7 may each consists of a nonmagnetic dielectric material such for instance as Si with a thickness ensuring the required de-coupling of the above defined magnztizations.
  • each of the said layers 3 and 7 may consists of a composite structure comprised of alternate thin layers or films of soft and hard materials. The individual thickness of such thin films is much lower than the thickness of the layers between which they intervene, i.e., the layers 2 and 4 and the layers 6 and 8.
  • the thin films of magnetically hard material duly block the magnetizations of the thin films of magnetically soft material but the structure does not present any leakage magnetic field nor any demagnetizing fields capable of influencing the layers between which it is inserted, consequently ensuring the required decoupling between said layers.
  • the second structure for the layer 3 is shown in FIG. wherein the thin layers 14, assumed of magnetically soft material, alternate with the layers 15, assumed of magnetically hard material.
  • layer 2 is made of a plurality of superposed relatively insulated thin films 12 and layer 14 is similarly made of a plurality of superposed relatively insulated thin films 13.
  • the material of the thin films 12 is a magnetically soft one.
  • the material of the thin films 13 is a magnetically hard one.
  • the relative insulation of the thin films is obtained by deposition of very thin insulating films between the thin magnetic films.
  • the layers 4 and 6 will have negligible action during a write-in operation whereas the action of the layers 2 and 8 will be efficient to define a width (e FIG. 4) of the magnetic airgap.
  • the recording fields will duly penetrate within the recording magnetic layer moving along the direction of the arrow S at close proximity of the airgap face of the transducer.
  • the action of the layers 2 and 8 will be nil during a read-out operation from such a moving record and the layers 4 and 6 will define the width of the read airgap (e,) which is substantially equal to the width of the geometrical airgap e.
  • the lateral lengths of the soft and hard material layers have been shown different as it is thought preferable to read on a reduced length of the magnetic record with respect to the length over which the record has been written. However, such a dimensioning is not deemed imperative per se so that lengthes L2 and L1 may be made equal if desired.
  • the magnetic transducer structures according to the invention have their read and write functions duly separated as the magnetically soft material layers are relatively tightly coupled and do not have any substantial leakage field therefrom and that, further, said soft material layers are decoupled from any magnetostatic damageable effect from the hard material layers and are consequently protected against the leakage fields from the said hard material layers.
  • a read/write transducer comprising: a pair of magnetic pole-pieces and read-write conductor means inductively coupled to said pole-pieces and passing therebetween; each pole-piece including the superposition of:
  • a read/write transducer according to claim 1, wherein said magnetostatically decoupling layer means is comprised of a non-magnetic dielectric material.
  • a read/write transducer according to claim 1, wherein said magnetostatically decoupling layer means comprises a stack of thin films of alternating magnetic materials one of which is of substantially lower permeability, substantially higher saturation flux density and appreciably higher value of anisotropy than the other one.
  • a read/write transducer according to claim 1, wherein said first magnetic layer member consists of a stack of relatively insulated thin magnetic films.
  • a read/write transducer according to claim 4, wherein said second magnetic layer member also consists of a stack of relatively insulated thin magnetic films.
  • a read/write transducer according to claim 1, wherein the material of said first magnetic layer member is an iron-nickel alloy and the material of said second magnetic layer member is selected from the group consisting of iron, cobalt and the iron-cobalt alloys.
  • a composite pole-piece structure comprising a stack of magnetic material thin films wherein a first plurality of said films close to the said conductor means are relatively insulated and of a first magnetic material, a second plurality of said films over the first plurality are directly contacting each other and alternate first and second magnetic materials, and a third plurality of said films are relatively insulated and of the said second magnetic material over the second plurality of thin films, and wherein the said second magnetic material is of substantially lower permeability, substantially higher saturation flux density and appreciably higher value of anisotropy field than the first magnetic material.
  • a read/write magnetic transducer comprising a pair of magnetic pole-pieces and read-write conductor means inductively coupled to the pole-pieces and passing therebetween, a composite pole-piece structure comprising a first plurality of relatively insulated thin film of a first magnetic material close to said read-write conductor means, a nonmagnetic dielectric material layer over first plurality of thin films, and a second plurality of relatively insulated thin films of a second magnetic material over said dielectric layer, the second magnetic material being of substantially lower permeability, substantially higher saturation flux density and appreciably higher value of anisotropy field than the

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Magnetic Heads (AREA)
  • Thin Magnetic Films (AREA)
  • Magnetic Record Carriers (AREA)
US409613A 1972-11-07 1973-10-25 Read-write magnetic transducer having a composite structure comprising a stack of thin films Expired - Lifetime US3867368A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7239317A FR2205701B1 (de) 1972-11-07 1972-11-07

Publications (1)

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US3867368A true US3867368A (en) 1975-02-18

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Country Link
US (1) US3867368A (de)
BE (1) BE806212A (de)
DE (1) DE2355672C3 (de)
ES (1) ES420322A1 (de)
FR (1) FR2205701B1 (de)
GB (1) GB1453288A (de)
HU (1) HU169854B (de)
IT (1) IT999733B (de)
NL (1) NL7314869A (de)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975773A (en) * 1974-03-11 1976-08-17 Compagnie Internationale Pour L'infomatique Thin film magnetic heads
US4044394A (en) * 1975-04-07 1977-08-23 Hitachi, Ltd. Thin film magnetic head with a center tap
US4156882A (en) * 1977-12-15 1979-05-29 Texas Instruments Incorporated Magnetic transducer
US4191983A (en) * 1977-06-24 1980-03-04 Applied Magnetics Corporation Thin film magnetic head assembly having a thin film magnetic transducer encapsulated in insulating bonding material
US4195323A (en) * 1977-09-02 1980-03-25 Magnex Corporation Thin film magnetic recording heads
EP0023390A1 (de) * 1979-06-27 1981-02-04 Matsushita Electric Industrial Co., Ltd. Magnetkopfanordnung
US4321641A (en) * 1977-09-02 1982-03-23 Magnex Corporation Thin film magnetic recording heads
WO1989005505A1 (en) * 1987-12-04 1989-06-15 Digital Equipment Corporation Laminated poles for recording heads
US4897749A (en) * 1988-03-16 1990-01-30 Magnetic Peripherals Inc. Combination probe and ring head for vertical recording
EP0414473A2 (de) * 1989-08-24 1991-02-27 Matsushita Electric Industrial Co., Ltd. Magnetkopfvorrichtung
US5108837A (en) * 1987-12-04 1992-04-28 Digital Equipment Corporation Laminated poles for recording heads
US5132859A (en) * 1990-08-23 1992-07-21 International Business Machines Corporation Thin film structures for magnetic recording heads
JPH04507271A (ja) * 1989-08-17 1992-12-17 キャタピラー インコーポレイテッド 自動掘削制御装置及び方法
US6259583B1 (en) 1998-09-16 2001-07-10 International Business Machines, Corporation Laminated yoke head with a domain control element
US20060098336A1 (en) * 2004-11-05 2006-05-11 Seagate Technology Llc Perpendicular recording head having controlled permeability and saturation moment
US20100119874A1 (en) * 2008-11-13 2010-05-13 Headway Technologies, Inc. Laminated high moment film for head applications

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2003647B (en) * 1977-09-02 1982-05-06 Magnex Corp Thin film magnetic recording heads
DE3424651A1 (de) * 1983-11-04 1985-05-15 Control Data Corp., Minneapolis, Minn. Magnetwandlerkopf

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3344237A (en) * 1967-09-26 Desposited film transducing apparatus and method op producing the apparatus
US3549825A (en) * 1967-09-18 1970-12-22 Ncr Co Magnetic transducer with planar spiral coil extending into the gap
US3564558A (en) * 1968-08-26 1971-02-16 Sperry Rand Corp High-density magnetic recording scheme
US3611417A (en) * 1969-07-30 1971-10-05 Sperry Rand Corp High-density magnetic recording method
US3639699A (en) * 1970-02-27 1972-02-01 Gen Electric Magnetic transducer having a composite magnetic core structure
US3700827A (en) * 1970-01-31 1972-10-24 Nippon Electric Co Magnetic head including thin magnetic film separated by a gap spacer
US3723665A (en) * 1969-10-28 1973-03-27 Commissariat Energie Atomique Integrated magnetic head having alternate conducting and insulating layers within an open loop of two magnetic films

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3344237A (en) * 1967-09-26 Desposited film transducing apparatus and method op producing the apparatus
US3549825A (en) * 1967-09-18 1970-12-22 Ncr Co Magnetic transducer with planar spiral coil extending into the gap
US3564558A (en) * 1968-08-26 1971-02-16 Sperry Rand Corp High-density magnetic recording scheme
US3611417A (en) * 1969-07-30 1971-10-05 Sperry Rand Corp High-density magnetic recording method
US3723665A (en) * 1969-10-28 1973-03-27 Commissariat Energie Atomique Integrated magnetic head having alternate conducting and insulating layers within an open loop of two magnetic films
US3700827A (en) * 1970-01-31 1972-10-24 Nippon Electric Co Magnetic head including thin magnetic film separated by a gap spacer
US3639699A (en) * 1970-02-27 1972-02-01 Gen Electric Magnetic transducer having a composite magnetic core structure

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975773A (en) * 1974-03-11 1976-08-17 Compagnie Internationale Pour L'infomatique Thin film magnetic heads
US4044394A (en) * 1975-04-07 1977-08-23 Hitachi, Ltd. Thin film magnetic head with a center tap
US4191983A (en) * 1977-06-24 1980-03-04 Applied Magnetics Corporation Thin film magnetic head assembly having a thin film magnetic transducer encapsulated in insulating bonding material
US4195323A (en) * 1977-09-02 1980-03-25 Magnex Corporation Thin film magnetic recording heads
US4321641A (en) * 1977-09-02 1982-03-23 Magnex Corporation Thin film magnetic recording heads
US4156882A (en) * 1977-12-15 1979-05-29 Texas Instruments Incorporated Magnetic transducer
EP0023390A1 (de) * 1979-06-27 1981-02-04 Matsushita Electric Industrial Co., Ltd. Magnetkopfanordnung
US5108837A (en) * 1987-12-04 1992-04-28 Digital Equipment Corporation Laminated poles for recording heads
WO1989005505A1 (en) * 1987-12-04 1989-06-15 Digital Equipment Corporation Laminated poles for recording heads
US4897749A (en) * 1988-03-16 1990-01-30 Magnetic Peripherals Inc. Combination probe and ring head for vertical recording
JPH04507271A (ja) * 1989-08-17 1992-12-17 キャタピラー インコーポレイテッド 自動掘削制御装置及び方法
EP0414473A3 (en) * 1989-08-24 1992-01-08 Matsushita Electric Industrial Co., Ltd. Magnetic head device
EP0414473A2 (de) * 1989-08-24 1991-02-27 Matsushita Electric Industrial Co., Ltd. Magnetkopfvorrichtung
US5132859A (en) * 1990-08-23 1992-07-21 International Business Machines Corporation Thin film structures for magnetic recording heads
US6259583B1 (en) 1998-09-16 2001-07-10 International Business Machines, Corporation Laminated yoke head with a domain control element
US20060098336A1 (en) * 2004-11-05 2006-05-11 Seagate Technology Llc Perpendicular recording head having controlled permeability and saturation moment
US7369360B2 (en) * 2004-11-05 2008-05-06 Seagate Technology Llc Perpendicular recording head having controlled permeability and saturation moment
US20080144220A1 (en) * 2004-11-05 2008-06-19 Seagate Technology Llc Perpendicular Recording Head Having Controlled Permeability and Saturation Moment
US20100119874A1 (en) * 2008-11-13 2010-05-13 Headway Technologies, Inc. Laminated high moment film for head applications
US8329320B2 (en) * 2008-11-13 2012-12-11 Headway Technologies, Inc. Laminated high moment film for head applications

Also Published As

Publication number Publication date
IT999733B (it) 1976-03-10
FR2205701A1 (de) 1974-05-31
NL7314869A (de) 1974-05-09
DE2355672A1 (de) 1974-05-16
ES420322A1 (es) 1976-03-16
DE2355672B2 (de) 1980-01-31
BE806212A (fr) 1974-02-15
HU169854B (de) 1977-02-28
DE2355672C3 (de) 1980-10-09
FR2205701B1 (de) 1977-08-05
GB1453288A (en) 1976-10-20

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