CA1076253A - Magnetic converter having a magnetoresistive element - Google Patents
Magnetic converter having a magnetoresistive elementInfo
- Publication number
- CA1076253A CA1076253A CA254,555A CA254555A CA1076253A CA 1076253 A CA1076253 A CA 1076253A CA 254555 A CA254555 A CA 254555A CA 1076253 A CA1076253 A CA 1076253A
- Authority
- CA
- Canada
- Prior art keywords
- magnetic
- strip
- current source
- current
- recording medium
- 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.)
- Expired
Links
Classifications
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
Abstract
ABSTRACT:
A magnetic converter having a magnetoresistive element. In order to be able to use a magnetoresistive element which couples a large height (and hence good resistan-ce to detrition) to a good reproduction of short wave signals, the resistance of the element is measured by means of an alternating current hving a frequency which is larger than
A magnetic converter having a magnetoresistive element. In order to be able to use a magnetoresistive element which couples a large height (and hence good resistan-ce to detrition) to a good reproduction of short wave signals, the resistance of the element is measured by means of an alternating current hving a frequency which is larger than
Description
"Magnetic converter having a magnetoresistive element".
., The invention relates to a magnetic converter for detecting infor~ation-representing magnetic fields on a magnetic recording medlum which is movable relative to the converter, comprising a substantially rectangular strip of magnetoresisti~e material ha~ing a free edge which is intended to face the recording medium, and two electric connections on opposite ends of the strip for connection to an electr$cal circuit for detecting resistance variations, said circuit com-prising a current source.
~agnetic converters in which a magnetoresistive element is used as a sensing element are known~ for example, from United States Patent Specifications 3,493,694 and 3,691,5400 The operatio~ of such magnetoresistive heads is based on the use of a strip-shaped element of a ferromagnetic, metallic ~`
material~ for example ~i-Fe, which is provided on a non magnetic substrate snd which is moved in the i~mediate proximity of, or in contact with, a magnetic recording medium for reproducing the information contents thereof. The field of the recording medium produces variations in the magnetic contition of tbe element and modulates the resistance thereof via the so~called magnetoresistance effect. This means that, when the recording medium passes the head9 the information-representing magnetic fields present on the medium rotate the spin system of the magnetoresistive element so that the resistance varies~ In this manner, the output signal of an external electrical circuit which is connected to the element assumes the form of current ': ' ; ~ "'' ~''~ ' "'''
., The invention relates to a magnetic converter for detecting infor~ation-representing magnetic fields on a magnetic recording medlum which is movable relative to the converter, comprising a substantially rectangular strip of magnetoresisti~e material ha~ing a free edge which is intended to face the recording medium, and two electric connections on opposite ends of the strip for connection to an electr$cal circuit for detecting resistance variations, said circuit com-prising a current source.
~agnetic converters in which a magnetoresistive element is used as a sensing element are known~ for example, from United States Patent Specifications 3,493,694 and 3,691,5400 The operatio~ of such magnetoresistive heads is based on the use of a strip-shaped element of a ferromagnetic, metallic ~`
material~ for example ~i-Fe, which is provided on a non magnetic substrate snd which is moved in the i~mediate proximity of, or in contact with, a magnetic recording medium for reproducing the information contents thereof. The field of the recording medium produces variations in the magnetic contition of tbe element and modulates the resistance thereof via the so~called magnetoresistance effect. This means that, when the recording medium passes the head9 the information-representing magnetic fields present on the medium rotate the spin system of the magnetoresistive element so that the resistance varies~ In this manner, the output signal of an external electrical circuit which is connected to the element assumes the form of current ': ' ; ~ "'' ~''~ ' "'''
-2-'' :'' :L~76~S3 or voltage fluctuations representing the information stored in the recording medium. For this purpose, the ends of the element are connected to a current source which supplies a measuring current which may be both a direct current and an alternating current. One end of the element is intended to face the recording medium during operation. For good opPration it is important that said edge be as near as possible to, and preferably in oontact with, the recording mldium. AS a result o~ this, however, the dimension of the element normal to said edge (the height) decreases during use as a result of detrition. In order to maintain good opera~ion of the element as long as possible, one would want to choose the height as large as possible, for example, 100 microns. For a good reproduction of short wavelengths, however, the height may not bP chosen to be too l æ ge and typically is from 5 to 10 micxons.
It is the object of the invention to provide a solution to this dilemma. In ac~ordance with this invention there is provided a magnetic con~er~er for detecting information-representing magnetic fields on a magnetic recording medium which is movable relative to the converter, comprising a 5ubstantially rectangular strip of magnetoresistive material, the width of said rectangular strip being substantially greater than the thickness thereof, and having a free edge which is intended to face the reoording medium, and two elect~ic connections on opposite a~ds of the strip for connection to an electric cixcuit for detecting resistance varia-~ions, said circult oomprising a current source, characterized in that the current source is ~esigned to supply a high frequency alternating current having a frequency ~3t which is larger than ~ , where /u is the magne~ic permeability in Henry/m of the magnetoresistive material,~ is ~he resistiv-ity in ohm.m and D is the cross-section in m .
By opexating the strip of magnebDresistive material with such a high frequency current, a current distribution occurs in the strip which is given by the laberal skin effect. Said current distribution is characterized by a concentration o~ the current at the sdges of the strip,
It is the object of the invention to provide a solution to this dilemma. In ac~ordance with this invention there is provided a magnetic con~er~er for detecting information-representing magnetic fields on a magnetic recording medium which is movable relative to the converter, comprising a 5ubstantially rectangular strip of magnetoresistive material, the width of said rectangular strip being substantially greater than the thickness thereof, and having a free edge which is intended to face the reoording medium, and two elect~ic connections on opposite a~ds of the strip for connection to an electric cixcuit for detecting resistance varia-~ions, said circult oomprising a current source, characterized in that the current source is ~esigned to supply a high frequency alternating current having a frequency ~3t which is larger than ~ , where /u is the magne~ic permeability in Henry/m of the magnetoresistive material,~ is ~he resistiv-ity in ohm.m and D is the cross-section in m .
By opexating the strip of magnebDresistive material with such a high frequency current, a current distribution occurs in the strip which is given by the laberal skin effect. Said current distribution is characterized by a concentration o~ the current at the sdges of the strip,
-3~
6;253 namely at the edge facing the recording medium and the opp~sibe-ly located ~dge. As a result of this it is possible with a comparatively large height of the strip to nevertheless achieve a large sensitivity.
A Gunn oscillator or L.S.A. oscillator is pre-ferably used as a current source in the device according to the invention. Oscillators of this type produce a sufficient power at the frequencies required m the scope of the in-vention.
The invention will be described in greater de-tail, by way of example, with reference to the drawing.
Figure 1 shows diagrammatically a magnetic converter having a magnetoresistive strip o the type to which the present invention relates.
Figure 2 is a sectional view of the magneto-resistive strip shown in Figure 1 ln which the current dis-tribution is shown which occurs in the construction acoording to the invention.
Figure 1 shcws a magnetic converter havin~ a strip 1 of magneboresistive material provided on a non-magnetic substrate 3 and connected to said strip is a current source 2.
The so~LAce 2 is a high-~requency ascillating current source which controls the measuring curr~nt Is through the strip 1.
The voltage be~w~en the terminals 7 and 8 of the strip 1 is denoted by Vs and is measured by means of the measuring m-strument 4. This voltage is a measure of the information-representing magnetic fields 6 originating fm m the magneto-recording medium 5 bo which the strip 1 is coupled magnetically.
'""'.
- , . , . ~ ~:
.. . . .
;Z53 The strip 1 is at right angles to the plane of the recording medium 5. The dimensions of the strip l are denoted by the latters a, b and c~ where a is the height of the strip, b is the thickness and c is the track width. For the str-lp 1, thin layers of material are used Qf which Ni-Fe having a ~hickness between 200 and ~000 ~ is the most usual.
When it is ensured that the curren~ source 2 produces a measuring current Is having a frequency ~t which is larger than 8 P b' and if a > > b~ which is just desired for the application as a magnetic head, the measuring current will be concentrated, as a result of the occurrence of the so-called lateral skin effect, on the two opposite edges of the s~rip l, as is shown in Figure 2, which is a sectional view of the strip 1, by means of the shaded area. It is to be ncted that the di~ension a in ma~netoresistive elemen~s is indeed many times larger than the di~ension b. For example, a = 100 /um and b = 0~1 /um. With a resistivity ~ = 15.10 8 ohm.m and a relative magne~ic pen~eability h r 10 the value of the limit frequency for such a s~rip (the frequency above which the lateraL skln effec~ occur~) then is 1519.8 MHz. This frequency is just in the range for which a sufficient power . . , is reached with Gunn or L. S.AA oscillators for the present appli~ation (lO mW in c.w~ operation, with efficiency of 2 to 5 ~a ) ~
As a result of the concentration of the current at the strip edges, the di~ensio~ a may be chosen to be so ~ --large that a larger resis~ance to detrition is achiev~d than ;
iS posslble in the known co~verters of the kind mentioned in ', ~
.. .. . . .. . , ,, . . . ~ .
,253 the preamble. As a is made larger, the demagnetizing field in the interior of the s~rip becomes smaller, so that the sen-sitivity to exte~nal fields increases and the loss of sen-sitivity by concentration of the measuring current at the edge of the strip 1 which is furthest away from ~he recording medium 5, is compensated for.
~;""
' ' ,~
' `'','' ' - . . . . .
6;253 namely at the edge facing the recording medium and the opp~sibe-ly located ~dge. As a result of this it is possible with a comparatively large height of the strip to nevertheless achieve a large sensitivity.
A Gunn oscillator or L.S.A. oscillator is pre-ferably used as a current source in the device according to the invention. Oscillators of this type produce a sufficient power at the frequencies required m the scope of the in-vention.
The invention will be described in greater de-tail, by way of example, with reference to the drawing.
Figure 1 shows diagrammatically a magnetic converter having a magnetoresistive strip o the type to which the present invention relates.
Figure 2 is a sectional view of the magneto-resistive strip shown in Figure 1 ln which the current dis-tribution is shown which occurs in the construction acoording to the invention.
Figure 1 shcws a magnetic converter havin~ a strip 1 of magneboresistive material provided on a non-magnetic substrate 3 and connected to said strip is a current source 2.
The so~LAce 2 is a high-~requency ascillating current source which controls the measuring curr~nt Is through the strip 1.
The voltage be~w~en the terminals 7 and 8 of the strip 1 is denoted by Vs and is measured by means of the measuring m-strument 4. This voltage is a measure of the information-representing magnetic fields 6 originating fm m the magneto-recording medium 5 bo which the strip 1 is coupled magnetically.
'""'.
- , . , . ~ ~:
.. . . .
;Z53 The strip 1 is at right angles to the plane of the recording medium 5. The dimensions of the strip l are denoted by the latters a, b and c~ where a is the height of the strip, b is the thickness and c is the track width. For the str-lp 1, thin layers of material are used Qf which Ni-Fe having a ~hickness between 200 and ~000 ~ is the most usual.
When it is ensured that the curren~ source 2 produces a measuring current Is having a frequency ~t which is larger than 8 P b' and if a > > b~ which is just desired for the application as a magnetic head, the measuring current will be concentrated, as a result of the occurrence of the so-called lateral skin effect, on the two opposite edges of the s~rip l, as is shown in Figure 2, which is a sectional view of the strip 1, by means of the shaded area. It is to be ncted that the di~ension a in ma~netoresistive elemen~s is indeed many times larger than the di~ension b. For example, a = 100 /um and b = 0~1 /um. With a resistivity ~ = 15.10 8 ohm.m and a relative magne~ic pen~eability h r 10 the value of the limit frequency for such a s~rip (the frequency above which the lateraL skln effec~ occur~) then is 1519.8 MHz. This frequency is just in the range for which a sufficient power . . , is reached with Gunn or L. S.AA oscillators for the present appli~ation (lO mW in c.w~ operation, with efficiency of 2 to 5 ~a ) ~
As a result of the concentration of the current at the strip edges, the di~ensio~ a may be chosen to be so ~ --large that a larger resis~ance to detrition is achiev~d than ;
iS posslble in the known co~verters of the kind mentioned in ', ~
.. .. . . .. . , ,, . . . ~ .
,253 the preamble. As a is made larger, the demagnetizing field in the interior of the s~rip becomes smaller, so that the sen-sitivity to exte~nal fields increases and the loss of sen-sitivity by concentration of the measuring current at the edge of the strip 1 which is furthest away from ~he recording medium 5, is compensated for.
~;""
' ' ,~
' `'','' ' - . . . . .
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A magnetic converter for detecting information representing magnetic fields on a magnetic recording medium which is movable relative to the converter, comprising a substantially rectangular strip of magnetoresistive material, the width of said rectangular strip being substantially greater than the thickness thereof, and having a free edge which is intended to face the recording medium, and two electric connec-tions on opposite ends of the strip for connection to an electric circuit for detecting resistance variations, said circuit com-prising a current source, characterized in that the current source is designed to supply a high frequency alternating current having a frequency wt which is larger than , where ? is the magnetic permeability in Henry/m of the magnetoresistive material, is the reisitivity in ohm.m and D is the cross-section in m2.
2. A device as claimed in Claim 1, characterized in that the current source is a Gunn oscillator.
3. A device as claimed in Claim 1, characterized in that the current source is an L.S.A. oscillator.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7507049A NL7507049A (en) | 1975-06-13 | 1975-06-13 | MAGNETIC CONVERSION DEVICE WITH MAGNETO RESISTANCE ELEMENT. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076253A true CA1076253A (en) | 1980-04-22 |
Family
ID=19823949
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,555A Expired CA1076253A (en) | 1975-06-13 | 1976-06-10 | Magnetic converter having a magnetoresistive element |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS522414A (en) |
| CA (1) | CA1076253A (en) |
| DE (1) | DE2624614C3 (en) |
| FR (1) | FR2354606A1 (en) |
| GB (1) | GB1487723A (en) |
| NL (1) | NL7507049A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6454394U (en) * | 1987-09-30 | 1989-04-04 | ||
| JPH04102215A (en) * | 1990-08-21 | 1992-04-03 | Sony Corp | Magnetic head |
-
1975
- 1975-06-13 NL NL7507049A patent/NL7507049A/en not_active Application Discontinuation
-
1976
- 1976-06-02 DE DE19762624614 patent/DE2624614C3/en not_active Expired
- 1976-06-10 GB GB2407976A patent/GB1487723A/en not_active Expired
- 1976-06-10 CA CA254,555A patent/CA1076253A/en not_active Expired
- 1976-06-11 FR FR7617674A patent/FR2354606A1/en active Granted
- 1976-06-11 JP JP6786776A patent/JPS522414A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2624614C3 (en) | 1980-07-10 |
| DE2624614B2 (en) | 1979-09-27 |
| NL7507049A (en) | 1976-12-15 |
| FR2354606A1 (en) | 1978-01-06 |
| FR2354606B1 (en) | 1981-09-18 |
| JPS5739441B2 (en) | 1982-08-21 |
| JPS522414A (en) | 1977-01-10 |
| GB1487723A (en) | 1977-10-05 |
| DE2624614A1 (en) | 1977-01-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |