Title: High-efficiency single-turn write head for high-speed recording
Abstract: A write element for a magnetoresistive ("MR") head or a giant magnetoresistive (GMR) head includes a yoke and a coil. The coil made of a microstrip transmission line. The coil is a single turn and is U-shaped. The yoke of the write element includes laminated bottom pole, and top pole which are made of thin layers of ferromagnetic material antiferromagnetically exchange coupled to each other through a very thin nonmagnetic metallic layer. The yoke is made of metallic superlattices exhibiting strong antiferromagnetic exchange coupling between ferromagnetic layers through thin nonmagnetic metallic layers. The coil and the yoke are intertwined to provide two or more flux interactions between them. The yoke has a symmetrical structure with three interconnect vias, thereby reducing the effective magnetic length of the yoke. The antiferromagnetically exchange-coupled yoke has a stable single domain structure that exhibits very high switching time and does not suffer from hysteresis losses.
Patent Number: 6,972,932 Issued on 12/06/2005 to Shukh, et al.
| Inventors:
|
Shukh; Alexander M. (Savage, MN);
Van Ek; Johannes (Minnetonka, MN)
|
| Assignee:
|
Seagate Technology LLC (Scotts Valley, CA)
|
| Appl. No.:
|
949407 |
| Filed:
|
September 6, 2001 |
| Current U.S. Class: |
360/317 |
| Intern'l Class: |
G11B 005/12.7 |
| Field of Search: |
360/317,318,126,970.1
216/22
437/200
|
References Cited [Referenced By]
U.S. Patent Documents
| 4860139 | Aug., 1989 | Hamilton.
| |
| 5032945 | Jul., 1991 | Aryle et al.
| |
| 5168409 | Dec., 1992 | Koyama et al.
| |
| 5184267 | Feb., 1993 | Mallary.
| |
| 5195005 | Mar., 1993 | Mallary et al.
| |
| 5311386 | May., 1994 | Mallary.
| |
| 5510295 | Apr., 1996 | Carbal et al.
| |
| 5717547 | Feb., 1998 | Young.
| |
| 6034847 | Mar., 2000 | Komuro et al.
| |
| 6064546 | May., 2000 | Takano et al.
| |
| 6198607 | Mar., 2001 | Cain et al.
| |
| 6256863 | Jul., 2001 | Saito et al.
| |
| 6285528 | Sep., 2001 | Akiyama et al.
| |
| 6292329 | Sep., 2001 | Sato et al.
| |
| 6524491 | Feb., 2003 | Liu et al.
| |
Other References
Jason Jury et al, "Design of a Single-turn Microstrip Write Head" Sep. 1999;
IEEE trans. on Magnetics, V.35, No. 1; pp 2547-2549.
Jury, J., et al., "Design of a Single-turn Microstrip Write Head for Ultra-high
Data Rate Recording", IEEE Transactions on Magnetics, 35 (5), pp. 2547-2549,(1999).
Mallary, M., et al., "A New Thin Film Head which Doubles the Flux through the
Coil", IEEE Transactions on Magnetics, 29 (6), pp. 3832-3836, (1993).
Mallary, M., et al., "Advanced Multi-Via Heads", IEEE Transactions on Magnetics,
30 (2), pp. 287-290, (1994).
Parkin, S., "Systematic Variation of the Strength and Oscillation Period of Indirect
Magnetic Exchange Coupling through the 3d, 4d, and 5d Trasition Metals", Physical
Review Letters, 67 (25), pp. 3598-3601, (1991).
|
Primary Examiner: Chen; Tianjie
Parent Case Text
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application Ser. No.
60/230,400 entitled "HIGH-EFFICIENCY SINGLE-TURN WRITE HEAD FOR HIGH-SPEED RECORDING",
filed Sep. 6, 2000 under 35 U.S.C. 119(e).
Claims
1. A thin film transducer comprising
a coil, wherein the coil is formed as a transmission line;
a first pole portion made of a laminated material; and
a second pole portion made of a laminated material, wherein the laminated material includes:
a first layer of ferromagnetic material;
a second layer of ferromagnetic material; and
a layer of nonmagnetic conductive material interposed between the first layer
of ferromagnetic material and the second layer of ferromagnetic material, wherein
the first layer of ferromagnetic material and the second layer of ferromagnetic
material are antiferromagnetically exchange coupled to each other through the layer
of nonmagnetic conductive material.
2. The thin film transducer of claim 1 wherein the first pole portion and the
second pole portion are planar.
3. The thin film transducer of claim 1 wherein the first pole portion has two
ends and the second pole portion has two ends, wherein the first pole portion and
the second pole portion are connected to one another between the ends of the first
pole portion and the second pole portion.
4. The thin film transducer of claim 1 wherein the coil is U-shaped.
5. The thin film transducer of claim 1 wherein the coil consists of a single turn.
6. The thin film transducer of claim 1 wherein the first pole portion is symmetrical.
7. The thin film transducer of claim 1 wherein the second pole portion is symmetrical.
8. A slider comprising:
a magneto resistive read element; and
a write element further comprising:
a coil wherein the coil is formed as a transmission line;
a first pole portion made of a laminated material; and
a second pole portion made of a laminate material, wherein each of the first
and second pole portions includes at least two layers of ferromagnetic material
which are separated by a layer of nonmagnetic conductive material and antiferromagnetically
exchange coupled to each other through the layer of nonmagnetic conductive material.
9. The slider of claim 8, wherein the ferromagnetic material is selected from
a group comprising Ni
45Fe
55, NiFeCo, and FeCo.
10. The slider of claim 8, wherein the nonmagnetic conductive material is selected
from the group comprising Ru, Rh, Re, and Cu.
11. The slider of claim 8, wherein the nonmagnetic conductive material is approximately
5 to 30 nm thick.
12. The slider of claim 8, further comprising a third pole portion adjacent the
second pole portion and a nonmagnetic material positioned between the second pole
portion and third pole portion.
13. The slider of claim 12, further comprising a fourth pole portion adjacent
the third pole portion and a nonmagnetic material positioned between the third
pole portion and fourth pole portion.
14. The slider of claim 13, wherein each of the third and fourth pole portion
comprises of a ferromagnetic material.
15. The slider of claim 14, wherein the ferromagnetic material is selected from
a group comprising Ni
45Fe
55, NiFeCo, and FeCo.
16. The slider of claim 8, wherein the coil is U-shaped.
17. The slider of claim 8, wherein the first pole portion and second pole portion
are intertwined with the coil to provide more than two flux interactions between
the first pole portion, the second pole portion and the coil.
18. The slider of claim 8, wherein the first and second pole portion each are
a planar symmetrical structure.
19. A thin film transducer comprising:
a first pole portion made of a first laminated material and a second pole portion
made of a second laminated material;
a single turn coil adjacent the first and second vole, the single turn coil structured
and positioned so that the single turn coil provides at least two flux interactions
between the first and second poles and the single turn coil; and
wherein the first and second laminated material includes:
a first layer of ferromagnetic material, a second layer of ferromagnetic material,
and a layer of Ru interposed between the first layer of ferromagnetic material
and the second layer of ferromagnetic material.
20. The slider of claim 19, further comprising a third pole portion adjacent
the second pole portion and a nonmagnetic material positioned between the second
pole portion and third pole portion.
21. The slider of claim 20, further comprising a fourth pole portion adjacent
the third pole portion and a nonmagnetic material positioned between the third
pole portion and fourth pole portion.
22. The slider of claim 21, wherein each of the third and fourth pole portion
comprises of a ferromagnetic material.
23. The slider of claim 19, further comprising a coil wherein the coil is formed
as a transmission line.
24. The thin film transducer of claim 23, wherein the coil is U-shaped.
25. The slider of claim 19, wherein the first and second pole portion each are
a planar symmetrical structure.
Description
FIELD OF THE INVENTION
This application relates generally to the field of electronic data storage and
retrieval. More particularly, this invention relates to a transducer which includes
a write element having a single-turn for high-speed magnetic recording with high efficiency.
BACKGROUND OF THE INVENTION
One of the key components of any computer system is a place to store data. One
common place for storing data in a computer system is on a disc drive. The most
basic parts of a disc drive are a disc that is rotated, an actuator that moves
a transducer to various locations over the disc, and electrical circuitry that
is used to write and read data to and from the disc. The disc drive also includes
circuitry for encoding data so that it can be successfully retrieved and written
to the disc surface. A microprocessor controls many of the operations of the disc
drive including control of a data channel which passes data between a computer
and the disc drive. Disc drive manufacturers are constantly increasing the amount
of data that can be stored on the discs of a disc drive. The number of tracks per
inch, the data density of bits or individual transitions within a track, as well
as the rotational speed of the disc have all been increased over the years to increase
the data capacity of disc drives. Increasing the data density within the track
and the rotational speed of the disc have necessitated improvements in the speed
or data rate of the data channel. In order to further increase the data capacity
of disc drives, the transducer must be able to write and read data at increased
data rates. In other words, the transducer will have to be able to write transitions
to the disc at an increased rate and will have to be able to read transitions from
the disc at an increased rate.
One type of transducer used in current disc drives is a giant magnetoresistive
("GMR") read/write head.
A GMR read/write head generally consists of two portions, a writer portion for
storing magnetically-encoded information on a magnetic disc and a reader portion
for retrieving magnetically-encoded information from the disc. The reader portion
typically consists of a bottom shield, a top shield, and a giant magnetoresistive
(GMR) sensor positioned between the bottom and top shields. Magnetic flux from
the surface of the disc causes rotation of the magnetization vector of a free layer
of the GMR sensor, which in turn causes a change in electrical resistivity of the
GMR sensor. The change in resistivity of the GMR sensor can be detected by passing
a current through the GMR sensor and measuring a voltage across the GMR sensor.
External circuitry then coverts the voltage information into an appropriate format
and manipulates that information as necessary.
The writer portion typically consists of a top and a bottom pole, which are separated
from each other at an air bearing surface of the writer by a gap layer, and which
are connected to each other at a region distal from the air bearing surface by
a back gap closer or back via. Positioned between the top and bottom poles are
one or more layers of conductive coils encapsulated by insulating layers. The writer
portion and the reader portion are often arranged in a merged configuration in
which a shared pole serves as both the top shield in the reader portion and the
bottom pole in the writer portion.
To write data to the magnetic media, an electrical current is caused to flow
through
the conductive coils to thereby induce a magnetic field across the write gap between
the top and bottom poles. By reversing the polarity of the current through the
coils, the polarity of the data written to the magnetic media is also reversed.
Because the top pole is generally the trailing pole of the top and bottom poles,
the top pole is used to physically write the data to the magnetic media. Accordingly,
it is the top pole that defines the track width of the written data. More specifically,
the track width is defined by the width of the top pole at the air bearing surface.
The data rate is one of the main characteristics of current disk drives. The
MR element or GMR element is a spin valve and has no inductance or reluctance.
As a result, the MR or GMR element can read at very high frequencies. As a result,
the read element is able to accommodate high data rates. The limiting portion of
hardware is the write element. The data rate of drives depends considerably on
recording head or write element parameters, such as inductance, core length, domain
structure, and resonance frequency. The inductance of the write head is defined
primarily by the number of coil turns. To support high-speed recording, the smallest
possible number of turns is highly desirable. Hence a write element with a single-turn
coil should have minimal inductance. However, the write field is proportional to
the number of coil turns and the write current. Decreasing the number of turns
will require an increase of the write current, which is quite difficult to provide
due to preamplifier limitations.
Current write elements use a coil. Conventional coils have problems at high
data rates or when operating at high frequency. When recording at high data rates,
the electrical wavelength is comparable to the coil dimensions. The result is that
the conventional coil conductor cannot be used due to extensive losses.
The switching time of the write element during recording depends on the length
and the domain structure of the yoke. Multidomain structure assumes the presence
of domain walls that have low mobility, resulting in an increase of the write element
switching time. Moreover, the domain walls cause power losses in the yoke that
are proportional to the coercivity of the yoke.
The ferromagnetic resonance in the yoke can limit the efficiency and frequency
range of the write element. To suppress that effect, the frequency of the ferromagnetic
resonance of the yoke needs to be increased. The frequency of the ferromagnetic
resonance increases with the increase of the effective anisotropy field of the
yoke or with the reduction of permeability of the yoke material.
Therefore, what is needed is a write element capable of supporting a high
data rate. A low reluctance, low inductance coil is needed. In addition, the coil
must be able to handle information changing at high frequency without excessive
loss in transmission. In addition, there is a need for a yoke with an increased
ferromagnetic resonance. None of the existing write elements satisfies the above-mentioned needs.
SUMMARY OF THE PROPOSED SOLUTION
The present invention relates to a merged giant magnetoresistance (GMR) head
for high data rate, and particularly, to the writing part of the head, which is
capable of recording at a very high speed. The write element has a laminated antiferromagnetically
exchange-coupled yoke and single-turn coil made of a microstrip transmission line.
The coil and the yoke are intertwined to provide two or more flux interactions
between them.
The write element includes a symmetrical planar magnetic yoke and single-turn
coil. The coil has a U-shape form and a microstrip transmission line structure.
The coil with the microstrip structure is capable of transmitting electrical signals
with minimal loss in gygohertz diapason. The yoke is formed into a figure eight
shape (∞-shape) and wrapped around the single-turn coil twice. That doubles
the effective number of turns without increasing coil resistance and results in
a substantial increase of the magnetic field produced by the write head. The yoke
has a symmetrical structure with three interconnect vias, thereby reducing the
effective magnetic length of the yoke. The yoke is made of metallic superlattices
exhibiting strong antiferromagnetic exchange coupling between ferromagnetic layers
through thin nonmagnetic metallic layers. The antiferromagnetically exchange-coupled
yoke has a stable single domain structure that exhibits very high switching time
and does not suffer from hysteresis losses.
For a fuller understanding of the nature and advantages of the present solution,
reference should be made to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded view of a disc drive with a multiple disc stack.
FIG. 2 is a schematic view of the drive electronics of the disc drive.
FIG. 3 is a plan view of a single-turn write element according to the present invention.
FIG. 4 is a view of the pole portions on a first level according to the present invention.
FIG. 5 is a view of the pole portions on a second level according to the present invention.
FIG. 6 is a cross-sectional view along line 6—6 of the write
element shown in FIG. 3.
FIG. 7 is a cross-sectional view along line 7—7 of the write
element shown in FIG. 3.
FIG. 8 is a cross-sectional view along line 8—8 of the write
element shown in FIG. 3.
FIG. 9 is a schematic side view of the yoke and single-turn coil of the write
element showing the double yoke-coil interaction according to the present invention.
FIG. 10 is a cross-sectional view along line 6—6 of a front
portion of the write element given in FIG. 3 with single-layer magnetic studs.
FIG. 11 is a cross-sectional view along line 6—6 of another
embodiment of a write element having laminated magnetic studs.
DETAILED DESCRIPTION
In the following detailed description of the preferred embodiments, reference
is made to the accompanying drawings which form a part hereof, and in which are
shown by way of illustration specific embodiments in which the invention may be
practiced. It is to be understood that other embodiments may be utilized and structural
changes may be made without departing from the scope of the present invention.
The invention described in this application is useful with all mechanical configurations
of disc drives having either rotary or linear actuation. In addition, the invention
is also useful in all types of devices which use magnetic write elements. For example,
the invention described could also be used in tape drives where magnetic transitions
are formed on magnetic tape.
FIG. 1 is a view of one type of device that uses a magnetic write element. FIG.
1 is an exploded of a disc drive
100 having a rotary actuator. The disc
drive
100 includes a housing or base
112, and a cover
114.
The base
112 and cover
114 form a disc enclosure. Rotatably attached
to the base
112 on an actuator shaft
118 is an actuator assembly
120. The actuator assembly
120 includes a comb-like structure
122
having a plurality of arms
123. Attached to the separate arms
123
on the comb
122, are load beams or load springs
124. Load beams or
load springs are also referred to as suspensions. Attached at the end of each load
spring
124 is a slider
126 which carries a magnetic transducer
150.
On the end of the actuator assembly
120 opposite the load springs
124
and the sliders
126 is a voice coil
128. The actuator assembly
120
is used to place the transducing in transducing relation with respect to the disc
134 so that magnetic transitions representing data can be written to a track
on the disc
134 or so that the magnetic transducer can read data from the
disc
134. It should be noted that this invention is applicable to sliders
having more than one transducer. As will be discussed in more detail below, the
transducer of the invention has a separate read element and write element.
Attached within the base
112 is a pair of magnets
130 and
131. The pair of magnets
130 and
131, and the voice coil
128
are the key components of a voice coil motor which applies a force to the actuator
assembly
120 to rotate it about the actuator shaft
118. Also mounted
to the base
112 is a spindle motor. The spindle motor includes a rotating
portion called the spindle hub
133. In this particular disc drive, the spindle
motor is within the hub. In FIG. 1, a number of discs
134 are attached to
the spindle hub
133. In other disc drives a single disc or a different number
of discs may be attached to the hub. The invention described herein is equally
applicable to such other disc drives.
As shown schematically in FIG. 2, the disc drive includes electronics packages.
These electronics packages include a data channel
200 which is used to encode
and place individual magnetic transitions representing data onto the disc
134,
and which is used to decode the individual magnetic transitions upon reading and
reassemble these into data. The data channel includes a preamp
202, a data
channel chip
204 and an interface
210 to a main computer. The electronics
also include servo control circuit
240 for determining the amount of current
that needs to be used with the voice coil
128 keep the transducer
150
over a desired track or to move the transducer
150 from one track to another
track on the disc
134. Although the schematic shows these circuits off the
disc drive
100, these circuits are generally part of the disc drive. In
many disc drives these circuits are found in one or more chips attached to a printed
circuit which is in turn attached to the base
112 of the disc drive
100.
FIG. 3 is a plan view of a single-turn write element
300 according to
the present invention. The single-turn write element
300 includes a yoke
400 and a coil
310. The write element
300 has a single-turn
coil
310 made as a microstrip transmission line. The coil
310 consists
of two conductive layers
311 and
313, isolated from each other by
insulating layer
312. The coil
310 is substantially U-shaped.
The coil
310 is formed as a transmission line so that through put signal
is maximized and the transmission is done without excessive losses. More particularly,
the coil
310 is a microstrip transmission line that has a conductive circuit
on top of a dielectric substrate with a ground plane below the substrate. The microstrip
transmission line avails itself of low cost production in large volume and no connecters
are required between the circuit elements, thereby reducing size and resulting
in very low losses. The two conductive layers
311 and
313, as well
as the insulative layer
312 between the conductive layers
311 and
313, are geometrically positioned to produce a frequency impedance match.
The size of the conductor, the spacing of the conductors with respect to the ground
plane, and the geometry of the ground plane all affect the conductance and inductance
of the conductors. The insulators and the separator are also spaced so that their
permicivity and permeability produces a matched impedance. The advantages of using
a coil
310 formed as a microstrip transmission line or a transmission line
is that the write element is capable of handling high frequency write current and
therefore can write data at a very high data rate.
Turning now to FIGS. 4 and 5, the geometry of the yoke
400 will be
discussed. The yoke
400 is comprised of four yoke portions
410,
420,
510,
520 of material in two planes. FIG. 4 is a view of the two yoke
portions
410,
420 on a first plane or first level. FIG. 5 is a view
of the two yoke portions
510,
520 on a second level or second plane.
As can be seen, each of the yoke portions
410,
420,
510,
520
are symmetrical. The yoke portions on the first plane
410,
420 overlap
the yoke portions
510,
520 on the second plane. The yoke portions
410,
420 of the on the first plane are interconnected with the yoke
portions on the second plane to form a substantially figure 8-shaped magnetic flux
path that wraps around the legs of the U-shaped coil
300. The yoke portions
410,
420 on the first plane are situated behind the yoke portions
510,
520 in FIG. 3. The yoke portion
410 connects to yoke
portion
520 via a first external magnetic stud
431 and a second magnetic
external stud
433. The yoke portion
420 connects to the yoke portion
510 by a central magnetic stud
432. Another magnetic stud
440
connects the yoke portion
520 and the yoke portion
420 at one end
of the flux path. At the other end of the flux path a small magnetic stud
450
is attached to yoke portion
410 and does not touch yoke portion
510.
A write gap
442 is formed. The
FIGS. 6,
7 and
8 are various cross sectional views of the write
element
300 shown in FIG. 3. Now looking at FIGS. 3,
6,
7,
8, the magnetic yoke
310 of the write element
300 consists
of a planar bottom pole
410,
510 and top pole
420,
520
with a nonmagnetic write gap
442 is formed at the air-bearing surface of
the slider. The yoke is wrapped around the U-shaped single-turn coil
310
twice, thus doubling the effective number of turns. To provide double interaction
between the coil
310 and the yoke
400, the bottom pole
410,
510 and top pole
420,
520, respectively, consist of forward
or front yoke portions
510,
520 on one plane and rear yoke portions
410,
420 on a second plane. The yoke portions
410,
420
have a nonmagnetic gap
430 between the yoke portions
410,
420.
The yoke portions
510,
520 have a nonmagnetic gap
530 between
the yoke portions
510,
520. The front portion
410 of the bottom
pole is connected to the rear portion
520 of the top pole
5 through
external magnetic studs
431 and
433. The front portion
510
of the top pole is connected to the rear portion
420 of the bottom pole
through the central magnetic stud
432. The cross-sectional area of the central
magnetic stud
432 is at least twice as large as the cross-sectional area
of the external stud
431 and
433. As shown in FIG. 8, the coil
310
is isolated from the yoke
400 by insulating layer
800. The write
gap
442 and throat height are defined by magnetic extension
450 of
the bottom pole.
Now looking at FIGS. 3-8, the flux path will be discussed.
The switching current in the coil
310 induces a magnetic flux flow within
the yoke
400 of the write element
300. The flux path is shown with
the aid of arrows carrying reference numerals in FIGS. 3,
6,
7 and
8. And arrow
810 and an arrow
812 show the flux path flow
from the write gap
442 through the yoke portion
510 and then passes
through the center stud
432 and upward through the yoke portion
420,
as depicted by arrows
820,
821 and
822 in FIGS. 7,
6
and
8, respectively. The flux path then includes passing through the top
stud
440, as depicted by arrow
830. The flux path, depicted by arrow
830, then passes into the yoke portion
520 and splits or substantially
splits into two different flux paths, as depicted by arrows
840 and
841.
The flux path substantially splits because the yoke element
520 is symmetrical
and the whole entire yoke
400 is also symmetrical in shape. Therefore, it
can be predicted with reasonable certainty that the flux path through yoke element
520 substantially splits and then passes through the external studs
431
and
433 to the yoke element
410, as depicted by reference numerals
850 and
851. The flux then passes through the yoke element
410,
as depicted by arrows
860 and to the small magnetic stud
450 that
is positioned so that it does not touch yoke portion
510 to produce the
write gap
442. The magnetic flux then bridges the write gap or passes through
the write gap
442 where the flux is then used to write transitions to the
surface of the disk
134. This essentially completes the loop and the flux
path that results from the current changes in the coil
310.
FIG. 9 is a schematic side view of the yoke and single-turn coil of the write
element showing the double yoke-coil interaction according to the present invention.
The yoke
400 intertwined with the single-turn coil
310 provides at
least two flux interactions between the yoke
400 and the coil
310.
The multiple flux interactions significantly increase the inductive coupling between
the yoke
400 and the coil
310. Thus, compared with write elements
that have only a single flux interaction, a given amount of flux conducted by the
yoke
400 during reading induces a greater electrical signal in the coil
310, and during writing an increased level of flux is generated in the yoke
400 in response to the write signal applied to the coil
310. In general,
the induced electrical signal (during reading) and the induced flux (during writing)
are increased by a factor equal to the increased number of flux interactions.
FIG. 10 is a cross-sectional view along line
6—
6 of a portion
of the write element given in FIG. 3 with single-layer magnetic studs. Yoke portions
410,
420, and
510 are shown in FIG. 10. The yoke portion
520
is not shown in FIG. 10. The center stud
432 and the extension
450
are made of a single metal layer. In this embodiment, the external magnetic studs
431,
433 are also made of a single metal layer. The magnetic stud
440 which connects the yoke portion
520 and the yoke portion
420
at one end of the flux path, although not shown, would also be made of a single
metal layer. Each of the yoke portions
410,
420,
510,
520
is formed as a laminated element. The laminated elements are made of a thin layer
of ferromagnetic material
1011 and
1013 antiferromagnetically exchange
coupled to each other through a very thin nonmagnetic metallic layer
1012.
The ferromagnetic layers
1011,
1013 have low coercivity, low magnetostriction
and high magnetic moment and are 30-100 nm thick. The ferromagnetic layers
1011,
1013 are made of materials such as Ni45Fe55, NiFeCo, or FeCo. The thin nonmagnetic
layers
1012 are made of Ru, Rh, Re, Cu, etc., and are 5-30 nm thick. The
thickness of the nonmagnetic layers
1013 corresponds to the maximum of the
exchange coupling field.
FIG. 11 is a cross-sectional view along line
6—
6 of another
embodiment of a write element having laminated magnetic studs. This particular
embodiment differs from the embodiment of FIG. 10 in that the magnetic studs
431,
432,
433,
440 and
450 which connect the various yoke
portions
410,
420,
510,
520 are also made of laminate
material. In other words, the single layer magnetic studs
431,
432,
433,
440 and
450 are replaced with studs formed of laminate
material. The ferromagnetic layers
1011,
1013 of the studs are made
of materials such as Ni45Fe55, NiFeCo, or FeCo. The thin nonmagnetic layers
1012
of the studs are made of Ru, Rh, Re, Cu, etc., and are 5-30 nm thick. The thickness
of the nonmagnetic layers
1013 of the studs corresponds to the maximum of
the exchange coupling field. The laminate layers are formed by alternating the
ferromagnetic layers
1011,
1013 and non-magnetic yet conductive layers
1012. The laminate material is formed by alternately sputtering a non-magnetic
layer
1012 and a magnetic layer
1011. Specifically the laminate material
is placed on a turntable and then the non-magnetic layer
1012 and the magnetic
layer
1011 are sputtered at the various turntable locations.
In one embodiment, the magnetic yoke
400 has a single domain state and
is made of antiferromagnetically exchange-coupled superlattices.
The resultant write element
300 is a very high speed, high efficiency
write element that is used as part of a transducer that includes a giant magneto
resistive head. The yoke
400 forming a figure-8 wrap around the coil
310
results in at least twice as much magnetic flux, being induced in the coil for
a given write current I
W passing through the coil. In addition to this
figure-8 wrap, the structure is unique and yields a write head capable of operating
at a high frequency while being highly efficient.
Forming the yoke portions
410,
420,
510,
520
of a laminate material also increases the efficiency and speed of the write element
300. The laminate material keeps a single domain on each layer of the laminate
in the magnetic structure. This speeds the flux transmission since less energy
has to be expended in flipping magnetic domains. The laminate material merely has
a series of coherent spins so that when magnetic flux is induced in a flux path
the domains must only be moved slightly rather than flipped. Coherent spinning
works by moving the magnetic flux within the layer through a certain number of
degrees and never requires a flipping of a domain within the structure itself.
As a result, the magnetic flux path is much quicker in transmitting the flux as
the laminate provides a structure which enables coherent spinning. The application
of antiferromagnetically exchange-coupled superlattices made of altered ferromagnetic
and nonmagnetic layers for the yoke formation, stabilizes the single domain structure
and increases the effective anisotropy of the yoke, thus reducing the switching
time of the write element and increasing recording speed.
The yoke portions
410,
420,
510,
520 are each symmetrical.
The resultant structure is also symmetrical which allows which provides for exact
knowledge of where the flux path will be located.
In addition to being symmetrical, the whole structure is short and compact which
limits the amount of reluctance of the coils. Since there is a shorter flux path,
the magnetic flux only has to travel a short distance in order to be presented
at the gap
442. The short, compact structure results in a low reluctance
which is the resistance to changes in magnetization. The low reluctance makes the
flux path capable of changing at much higher frequencies so that transitions may
be written at higher frequencies and data rates. The structure could be approximately
10-12 microns in height and could be approximately 10-12 microns in width.
Since the coil
310 has very few turns, the coil has a low inductance.
The coil is basically a single-turn coil. Inductance is proportional to the number
of turns in the coil squared. The low inductance allows for the magnetic flux within
the flux path to change quickly. In other words, the low inductance enables the
flux to change quickly.
Still another aspect that makes the write element
300 capable of high
frequency operation is that the coil
310 is formed as a transmission line.
Still a further advantage is that the properties of U-shaped transmission lines
are known and can be easily accommodated by those in the disc drive industry.
Advantageously, the write element
300 has a low inductance,
because of the number of turns and a low reluctance because it can be made very
small. The use of a transmission line for the coil
310 allows for high frequency
current somewhere in the neighborhood of 1 megahertz. The use of the laminate for
the flux path prevents domains from being flipped, which also takes time. The end
result is a magnetic write element that can be used to produce very high rates
of data transmission. Data rates of 2 gigabytes per second are achievable using
this invention. It is contemplated that much higher write rates may also be achievable.
CONCLUSION
A thin film transducer includes a coil and a yoke. The coil of the transducer
is
formed as a transmission line. The coil is U-shaped. The yoke and coil are intertwined
to provide more than two flux interactions between the yoke and the coil. The yoke
is a planar, symmetrical structure. The yoke also includes a first pole portion
made of a laminated material, and a second pole portion made of a laminated material.
The laminated material includes a first layer of ferromagnetic material, a second
layer of ferromagnetic material, and a layer of nonmagnetic conductive material
interposed between the first layer of ferromagnetic material and the second layer
of ferromagnetic material. The first layer of ferromagnetic material and the second
layer of ferromagnetic material are antiferromagnically exchange coupled to each
other through the layer of nonmagnetic conductive material. The first pole portion
and the second pole portion are planar. The first pole portion has two ends and
the second pole portion has two ends. The first pole portion and the second pole
portion are connected to one another between the ends of the first pole portion
and the second pole portion. The coil is U-shaped and consists of a single turn.
The first pole portion is symmetrical and the second pole portion is symmetrical.
A slider includes a magneto resistive read element and a write element. The write
element of the slider further includes a coil formed as a transmission line, and
a yoke. The yoke is symmetrical and the yoke and coil are intertwined to provide
more than two flux interactions between the yoke and the coil. The yoke forms a
figure 8 around the coil to provide more than two flux interactions between the
yoke and the coil. The first pole portion is made of a laminated material, and
the second pole portion is made of a laminated material. The laminated material
includes a first layer of ferromagnetic material, a second layer of ferromagnetic
material, and a layer of nonmagnetic conductive material interposed between the
first layer of ferromagnetic material and the second layer of ferromagnetic material.
The two layers of ferromagnetic material in each of the first and second pole portions
are separated by a layer of nonmagnetic conductive material. The two layers of
ferromagnetic material in each of the first and second pole portions are antiferromagnically
exchange coupled to each other through the layer of nonmagnetic conductive material.
A disc drive which uses the slider with a magneto resistive read element, and
a
write element further having a coil formed as a transmission line, and a yoke,
also includes a base, a disc rotatably attached to the base, and an actuator assembly
attached to the base. The actuator assembly includes the slider. The actuator assembly
is adapted to move the slider between selected positions on the disc. The actuator
assembly also includes a voice coil motor for moving the actuator assembly, and
a control circuit for controlling the movement of the actuator assembly by controlling
the amount of current provided to the voice coil motor. The disc drive of also
includes a data channel.
A transducer includes a magneto resistive read element, and a write element.
The
write element includes a mechanism for providing a high frequency write current;
and a yoke.
It is to be understood that the above description is intended to be illustrative,
and not restrictive. Many other embodiments will be apparent to those of skill
in the art upon reviewing the above description. The scope of the invention should,
therefore, be determined with reference to the appended claims, along with the
full scope of equivalents to which such claims are entitled.
*
