US20140254047A1 - Reader with decoupled magnetic seed layer - Google Patents

Reader with decoupled magnetic seed layer Download PDF

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Publication number
US20140254047A1
US20140254047A1 US13/791,334 US201313791334A US2014254047A1 US 20140254047 A1 US20140254047 A1 US 20140254047A1 US 201313791334 A US201313791334 A US 201313791334A US 2014254047 A1 US2014254047 A1 US 2014254047A1
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US
United States
Prior art keywords
shield
base
sensor
seed layer
sensor stack
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US13/791,334
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English (en)
Inventor
Victor Boris Sapozhnikov
Taras Grigoryevich Pokhil
Mohammed Sharia Ullah Patwari
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Seagate Technology LLC
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Seagate Technology LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seagate Technology LLC filed Critical Seagate Technology LLC
Priority to US13/791,334 priority Critical patent/US20140254047A1/en
Assigned to SEAGATE TECHNOLOGY LLC reassignment SEAGATE TECHNOLOGY LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PATWARI, MOHAMMED SHARIA ULLAH, POKHIL, TARAS GRIGORYEVICH, SAPOZHNIKOV, VICTOR BORIS
Priority to JP2014041683A priority patent/JP6105506B2/ja
Priority to EP14158162.9A priority patent/EP2775476A3/en
Priority to KR1020140027166A priority patent/KR101590438B1/ko
Priority to CN201410082831.8A priority patent/CN104036791A/zh
Priority to US14/445,916 priority patent/US8970994B2/en
Publication of US20140254047A1 publication Critical patent/US20140254047A1/en
Priority to US14/636,967 priority patent/US9153251B2/en
Abandoned legal-status Critical Current

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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
    • G11B5/10—Structure or manufacture of housings or shields for heads
    • G11B5/11—Shielding of head against electric or magnetic fields
    • 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
    • G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
    • G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
    • G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
    • G11B5/3906—Details related to the use of magnetic thin film layers or to their effects
    • G11B5/3912—Arrangements in which the active read-out elements are transducing in association with active magnetic shields, e.g. magnetically coupled shields
    • 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
    • G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
    • G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
    • G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
    • G11B5/3906—Details related to the use of magnetic thin film layers or to their effects
    • G11B5/3929—Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding
    • 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
    • G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
    • G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
    • G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
    • G11B5/398—Specially shaped layers

Definitions

  • a magnetic read/write head includes a reader portion having a magnetoresistive (MR) sensor for retrieving magnetically encoded information stored on a magnetic disc.
  • MR magnetoresistive
  • Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor.
  • the change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor.
  • External circuitry then converts the voltage information into an appropriate format and manipulates that information to recover the information encoded on the disc.
  • Implementations described and claimed herein provide an apparatus comprising a base shield and a sensor stack, wherein the base shield is separated from the sensor stack via a first soft magnetic layer that is magnetically decoupled form the base shield.
  • FIG. 1 illustrates a perspective view of an example recording device using a reader disclosed herein.
  • FIG. 2 illustrates a schematic block diagram of an example implementation of the reader disclosed herein.
  • FIG. 3 illustrates another schematic block diagram of an example implementation of the reader disclosed herein.
  • FIG. 4 illustrates another schematic block diagram of an example implementation of the reader disclosed herein.
  • FIG. 5 illustrates another schematic block diagram of an example implementation of the reader disclosed herein.
  • FIG. 6 illustrates a graph of a transition readback signal obtained by an example reader disclosed herein.
  • FIG. 7 illustrates a graph of the PW50 gain as a measure of thickness of the soft decoupled magnetic layer for an example reader disclosed herein.
  • Giant Magnetoresistive (GMR) sensors that have increased sensitivity consist of two soft magnetic layers separated by a thin conductive, non-magnetic spacer layer such as copper.
  • Tunnel Magnetoresistive (TMR) sensors provide an extension to GMR in which the electrons travel with their spins oriented perpendicularly to the layers across a thin insulating tunnel barrier.
  • An antiferromagnetic (AFM) material (called the “pinning layer (PL)”) is placed adjacent to the first soft magnetic layer to prevent it from rotating. AFM materials exhibiting this property are termed “pinning materials”. With its rotation inhibited, the first soft layer is termed the “pinned layer”. The second soft layer rotates freely in response to an external field and is called the “free layer (FL).”
  • a common way to achieve stabilization is with a permanent magnet abutted junction design.
  • permanent magnets with high coercive field i.e., hard magnets
  • the field from the permanent magnets stabilizes the sensor and prevents edge domain formation, as well as provides proper bias.
  • synthetic antiferromagnet SAF
  • AFM/PL allows for consistent and predictable orientation of the SAF structure.
  • AFM/PL also provides stable structure to enable high amplitude linear response for a reader using the MR sensor.
  • the assembly of the various layers the GMR/TMR sensors, as discussed above, is also referred to as a sensor stack.
  • Such sensor stack may be surrounded by a base shield and a top shield to shield the sensor from any magnetic influences that are generated from other components of the transducer head.
  • the distance between the top shield and the base shield is referred to as the shield-to-shield spacing (SSS).
  • SSS shield-to-shield spacing
  • the pulse width fluctuations PW50 of magnetic sensors which determine the signal-to-noise (SNR) ratio in a recording system depends on the SSS of the header. Specifically, a reduction in the SSS leads to reduction in the value of the PW50 and therefore, an increase in the value of the SNR for the recording system.
  • SSS reduction to achieve lower PW50 has its limits.
  • the reader sensor assembly provides alternative methods for reducing the PW50 of a reader sensor without reducing the SSS of the reader sensor.
  • the reader sensor assembly includes reader stack surrounded by base shield and a top shield wherein at least one of the base shield and the top shield is separated from the sensor stack by a soft magnetic seed layer that is decoupled from the base shield or the top shield, respectively.
  • a soft magnetic seed layer that is decoupled from the base shield or the top shield, respectively.
  • only a portion of the soft magnetic seed layer is decoupled from the base shield or the top shield. Providing such partial decoupled seed layer allows to maintain the stability of the sensor while at the same time decreasing the PW50 of the sensor stack to improve the SNR of the recording system.
  • FIG. 1 illustrates a perspective view of an example recording device 100 using a reader disclosed herein.
  • the recording device 100 includes a disc 102 , which rotates about a spindle center or a disc axis of rotation 104 during operation.
  • the disc 102 includes an inner diameter 106 and an outer diameter 108 between which are a number of concentric data tracks 110 , illustrated by circular dashed lines.
  • the data tracks 110 are substantially circular and are made up of regularly spaced patterned bits 112 , indicated as dots or ovals on the disc 102 as well as in an exploded view 140 . It should be understood, however, that the described technology may be employed with other types of storage media, including continuous magnetic media, discrete track (DT) media, etc.
  • DT discrete track
  • a transducer head 124 is mounted on an actuator assembly 120 at an end distal to an actuator axis of rotation 122 and the transducer head 124 flies in close proximity above the surface of the disc 102 during disc operation.
  • the actuator assembly 120 rotates during a seek operation about the actuator axis of rotation 122 positioned adjacent to the disc 102 .
  • the seek operation positions the transducer head 124 over a target data track of the data tracks 110 .
  • the exploded view 140 illustrates data tracks 142 and an expanded view of a transducer head 144 having a writer 148 and a reader sensor 150 .
  • an example implementation of the reader sensor 150 is illustrated by a block diagram 160 .
  • the block diagram 160 illustrates an air-bearing surface (ABS) view of the reader sensor 150 .
  • the reader sensor 150 is illustrated to include a base shield 162 and a top shield 164 , with a sensor stack 166 formed between the base shield 162 and the top shield 164 .
  • the sensor stack 166 is separated from the base shield 162 by a base seed layer 168 that is at least partially decoupled from the base shield 162 .
  • a center portion 170 of the base seed layer 168 is not decoupled from the base shield 162
  • the outer portion 172 of the base seed layer 168 is decoupled from the base shield 162 .
  • the sensor stack 166 is separated from the top shield 164 by a top seed layer 174 that is at least partially decoupled from the top shield 164 .
  • a center portion 176 of the top seed layer 174 is not decoupled from the top shield 164
  • the outer portion 178 of the top seed layer 174 is decoupled from the top shield 164 .
  • the base seed layer 162 and the top seed layer 174 may be made of soft magnetic seed layer material and providing one or both of the base seed layer 162 and the top seed layer 174 results in decreased PW50 for the sensor 150 .
  • providing the partial coupled magnetic layers in the outer portions of the one or both of the base seed layer 162 and the top seed layer results in increased stability of the sensor 150 .
  • FIG. 2 illustrates a schematic block diagram of an ABS view of an example implementation of the reader 200 disclosed herein.
  • the reader 200 includes a base shield 210 and a top shield 212 around a sensor stack 214 .
  • the base shield 210 and the top shield 212 may be made of may be made of a magnetic material, such as NiFe, NiFeCu, NiCoFe, etc.
  • the reader 200 includes a decoupled base seed layer 216 on the surface of the base shield 210 .
  • the base shield 210 is separated from the sensor stack 214 by the decoupled base seed layer 216 .
  • the decoupled base seed layer 216 is magnetically decoupled from the base shield layer 210 .
  • the decoupled base seed layer 216 is made of soft magnetic material such as NiFe, NiFeCu, NiCoFe, etc and is separated from the base shield 210 by a thin layer of non-magnetic material 218 that is between the decoupled base seed layer 216 and the base shield 210 .
  • a thin layer of non-magnetic material 218 may be created using a dusting of the non-magnetic material on the base shield 210 or on the decoupled base seed layer 216 .
  • non-magnetic material include Tantalum, Tantalum compounds, etc.
  • the decoupled base seed layer 216 improves the PW50 of the reader 200 because the effective in-plane exchange coupling between the base shield 210 and the decoupled base seed layer 216 is very low or substantially equal to zero.
  • the closeness of the surfaces in the decoupled base seed layer 216 results in higher ratio of the Zeeman energy to the exchange energy, wherein the Zeeman energy is the energy between the base seed layer 216 and the media from which the data is read.
  • the higher Zeeman energy/exchange energy ratio results in easier change in the local magnetization direction as the sensor moves over the media, thus improving the PW50 of the sensor 200 .
  • the improved PW50 increases the capability of the sensor 200 to read data with higher linear density, thus allowing a recording device using the sensor 200 to provide higher linear data density and thus more cost effective data storage capabilities.
  • the thickness of the seed layer 216 may be 5-15 nm.
  • the thickness of the decoupled base seed layer 216 determines the exchange of magnetic energy between the base shield 210 and the decoupled base seed layer 216 . Specifically, if the decoupled base seed layer 216 is too thin, it would not be able to accommodate the magnetic flux from the media. On the other hand, if the decoupled base seed layer 216 is too thick, it reduces the PW50 gain.
  • FIG. 3 illustrates another schematic block diagram of an ABS view of an example implementation of the reader 300 disclosed herein.
  • the reader 300 includes a base shield 310 and a top shield 312 around a sensor stack 314 .
  • the base shield 310 and the top shield 312 may be made of may be made of a magnetic material, such as NiFe, NiFeCu, NiCoFe, etc.
  • the reader 300 also includes a decoupled base seed layer 316 on the surface of the base shield 310 and a decoupled top seed layer 318 on the surface of the top shield 312 .
  • the decoupled base seed layer 316 is magnetically decoupled from the base shield 310 and the decoupled top seed layer 318 is magnetically decoupled from the top shield 312 .
  • each of the decoupled base seed layer 316 and the decoupled top seed layer 318 is made of soft magnetic material such as NiFe, NiFeCu, NiCoFe, etc.
  • the forming of the decoupled seed layers 316 and 318 increases the ratio of the Zeeman energy to exchange energy on both sides of the sensor 314 , resulting in improved PW50 for the reader 300 .
  • FIG. 4 illustrates another schematic block diagram of an ABS view of an example implementation of the reader 400 disclosed herein.
  • the reader 400 includes a base shield 410 and a top shield 412 around a sensor stack 414 .
  • the base shield 310 and the top shield 312 may be made of a magnetic material, such as NiFe, NiFeCu, NiCoFe, etc.
  • the reader 400 also includes a decoupled top seed layer 418 on the surface of the top shield 412 .
  • the decoupled top seed layer 418 is magnetically decoupled from the top shield 412 .
  • the decoupled top seed layer 418 is made of soft magnetic material such as NiFe, NiFeCu, NiCoFe, etc.
  • the forming of the decoupled top seed layer 418 increases the ratio of the Zeeman energy to exchange energy on top shield side of the sensor 414 , resulting in improved PW50 for the reader 400 .
  • FIG. 5 illustrates another schematic block diagram of a side view (not to scale) of an example implementation of a reader 500 disclosed herein.
  • the reader 500 includes a sensor stack 512 with each of a base shield 514 and a top shield 516 on each sides of the sensor stack. Note that for the clarity of illustration, the distance between the base shield 514 and the sensor stack 512 is illustrated to be different than the distance between the top shield 516 and the sensor stack 512 .
  • the reader 500 may be part of a transducer head moving on an ABS 520 .
  • the base shield 514 includes a base seed layer 522 that is formed on the surface facing the sensor stack 512 .
  • the top shield 516 also includes a top seed layer 524 that is formed on the surface facing the sensor stack 512 .
  • Each of the base seed layer 522 and the top seed layer 524 includes a center portion that is decoupled from the base shield 514 and the top shield 516 , respectively.
  • the base seed layer 522 includes a decoupled base seed layer 526 that is magnetically decoupled from the base shield 514 .
  • the remaining base seed layer 522 is magnetically coupled with the base shield 514 .
  • the top seed layer 524 includes a decoupled top seed layer 528 that is magnetically decoupled from the top shield 516 .
  • the remaining top seed layer 524 is magnetically coupled with the top shield 516 .
  • the base center portions 526 and 528 are illustrated to have a square shape, in an alternative implementation, these center portions may also have other shapes, such as rectangular, circular, oval, etc.
  • the distances between the edges of the sensor stack 512 and the edges of the decoupled center portions 526 and 528 are at least twice the SSS.
  • the distance 530 between an edge of the sensor stack 512 and an edge of the top center portion 528 must be at least twice the SSS 532 (note that the distances as seen in the figures are not to scale).
  • the total width 534 (and length) of the top center portion 528 is greater than the 4*SSS 532 . Similar dimensions also apply to the base center portion 526 of the bottom seed layer 522 .
  • Such dimensions of the coupled base seed layer 522 and the top seed layer 524 ensure that the stability of the reader 500 is not adversely affected in view of the introduction of the base center portion 526 that is decoupled to the base shield 514 and the top center portion 528 that is decoupled from the top shield 516 .
  • the reader 500 includes the decoupled portions in the base seed layer 522 and the top seed layer 524 in the vicinity of the sensor stack 512 , the reader 500 exhibits lower PW50 and therefore higher linear density capabilities. However, because only a small portion of each of the base seed layer 522 and the top seed layer 524 is decoupled from the base shield 514 and the top shield 516 respectively, the reader 500 also provides higher stability compared to a reader where entire base seed layer and top seed layer were decoupled from a base shield and a top shield, respectively.
  • FIG. 6 illustrates a graph 600 of improvement in the transition readback signal obtained by an example reader disclosed herein.
  • the graph 600 illustrates a line 610 that represents the readback derivative without any decoupled seed layer on either of the base shield and the top shield and a line 612 that represents the readback derivative with a decoupled seed layer on the base shield.
  • the PW50 as illustrated by the line 620 is higher for the readback derivative 610 compared to the readback derivative 612 .
  • the PW50 improved from 28.2 nm to 27.1 nm, resulting in increased linear density capabilities for the reader.
  • FIG. 7 illustrates a graph 700 of modeled gain in PW50 as a function of magnetic layer thickness for an example reader disclosed herein.
  • graph 700 includes a line 710 illustrating the PW50 of a sensor without any decoupled seed layer between a sensor stack and a base shield layer.
  • the line 712 illustrates the PW50 as a function of the thickness of a decoupled seed layer formed on the base shield.
  • the difference between the line 710 and 712 is the decrease in the PW50 of the sensor resulting from the introduction of the decoupled seed layer between the base shield and the sensor stack.
  • the PW50 improves by approximately 1.1 nm (28.2 nm-27.1 nm). This improvement has also been observed experimentally.
  • the decrease in the PW50 decreases.
  • the decreased PW50 improves linear density capabilities of the reader.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Magnetic Heads (AREA)
  • Hall/Mr Elements (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Burglar Alarm Systems (AREA)
US13/791,334 2013-03-08 2013-03-08 Reader with decoupled magnetic seed layer Abandoned US20140254047A1 (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US13/791,334 US20140254047A1 (en) 2013-03-08 2013-03-08 Reader with decoupled magnetic seed layer
JP2014041683A JP6105506B2 (ja) 2013-03-08 2014-03-04 ベースシールドおよびセンサスタックを備えた装置、ならびにリーダセンサ
EP14158162.9A EP2775476A3 (en) 2013-03-08 2014-03-06 Reader with decoupled magnetic seed layer
KR1020140027166A KR101590438B1 (ko) 2013-03-08 2014-03-07 분리된 자기 시드층을 갖는 판독기
CN201410082831.8A CN104036791A (zh) 2013-03-08 2014-03-07 具有磁解耦的籽晶层的读取器
US14/445,916 US8970994B2 (en) 2013-03-08 2014-07-29 Reader with decoupled magnetic seed layer
US14/636,967 US9153251B2 (en) 2013-03-08 2015-03-03 Reader with decoupled magnetic seed layer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US13/791,334 US20140254047A1 (en) 2013-03-08 2013-03-08 Reader with decoupled magnetic seed layer

Related Child Applications (1)

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US14/445,916 Division US8970994B2 (en) 2013-03-08 2014-07-29 Reader with decoupled magnetic seed layer

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US20140254047A1 true US20140254047A1 (en) 2014-09-11

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US13/791,334 Abandoned US20140254047A1 (en) 2013-03-08 2013-03-08 Reader with decoupled magnetic seed layer
US14/445,916 Active US8970994B2 (en) 2013-03-08 2014-07-29 Reader with decoupled magnetic seed layer
US14/636,967 Active US9153251B2 (en) 2013-03-08 2015-03-03 Reader with decoupled magnetic seed layer

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US14/445,916 Active US8970994B2 (en) 2013-03-08 2014-07-29 Reader with decoupled magnetic seed layer
US14/636,967 Active US9153251B2 (en) 2013-03-08 2015-03-03 Reader with decoupled magnetic seed layer

Country Status (5)

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US (3) US20140254047A1 (enrdf_load_stackoverflow)
EP (1) EP2775476A3 (enrdf_load_stackoverflow)
JP (1) JP6105506B2 (enrdf_load_stackoverflow)
KR (1) KR101590438B1 (enrdf_load_stackoverflow)
CN (1) CN104036791A (enrdf_load_stackoverflow)

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US8970994B2 (en) 2015-03-03
US9153251B2 (en) 2015-10-06
US20140334042A1 (en) 2014-11-13
JP6105506B2 (ja) 2017-03-29
EP2775476A3 (en) 2015-03-04
JP2014175038A (ja) 2014-09-22
KR101590438B1 (ko) 2016-02-01
US20150243305A1 (en) 2015-08-27
EP2775476A2 (en) 2014-09-10
CN104036791A (zh) 2014-09-10
KR20140110788A (ko) 2014-09-17

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