WO1991000593A1 - Dispositif a memoire magnetique avec support d'enregistrement et tete magnetique a couche mince - Google Patents

Dispositif a memoire magnetique avec support d'enregistrement et tete magnetique a couche mince Download PDF

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Publication number
WO1991000593A1
WO1991000593A1 PCT/EP1990/000746 EP9000746W WO9100593A1 WO 1991000593 A1 WO1991000593 A1 WO 1991000593A1 EP 9000746 W EP9000746 W EP 9000746W WO 9100593 A1 WO9100593 A1 WO 9100593A1
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WO
WIPO (PCT)
Prior art keywords
magnetic
layer
leg
storage device
leading
Prior art date
Application number
PCT/EP1990/000746
Other languages
German (de)
English (en)
Inventor
Herbert Schewe
Dietrich Stephani
Original Assignee
Siemens Aktiengesellschaft
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 Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO1991000593A1 publication Critical patent/WO1991000593A1/fr

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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

Definitions

  • the invention relates to a magnetic data storage device
  • the magnetic guide body of which designed like a ring head and guiding the magnetic flux, contains two magnetic legs, a) each having at least one magnetic layer which forms a magnetic pole at its end facing the recording medium, b) the magnetic poles of which, viewed in the (relative) direction of movement of the head, are arranged one behind the other and with a small gap width to one another, c) the leg parts, which are further spaced apart from the gap width and have an interstice delimiting them, through which the windings of a write / read coil winding extend , and d) which are each provided with a magnetic reinforcement layer outside the region of their pole ends, wherein these reinforcement layers form corresponding parts of the outer sides of the magnetic guide body and the one facing the substrate in the (relative) direction of movement the reinforcing layer assigned to the leading magnetic leg is arranged such that a protruding opposite the pole end of the associated magnetic leg there is a certain (vert
  • Thin-film magnetic heads designed for these types of magnetization generally have a guide body made of magnetizable material for guiding the magnetic flux, which can have a shape similar to a ring shape with two magnetic legs. These magnetic legs form magnetic poles at their ends facing the recording medium, which are arranged one behind the other as seen in the relative direction of movement of the head with respect to the recording medium. A narrow gap is formed between the pole ends of the magnetic legs. Outside the region of these pole ends, the magnetic legs delimit an intermediate space which is correspondingly widened due to an increase in the mutual distance between the magnetic legs.
  • the conductors of at least one read / write coil winding extend through this intermediate space.
  • each of the magnetic legs of this magnetic head also contains a magnetic reinforcement layer outside the pole area.
  • This to improve the flow or reinforcement layers serving to lower the magnetic resistance in the magnetic guide body are arranged such that they largely form the outer sides of the magnetic guide body.
  • This guide body should be constructed on the back of a non-magnetic substrate using thin-film technology, the substrate being designed as a so-called missile. It can thus be guided aerodynamically over a plate-shaped recording medium which is not specified in the European patent application mentioned.
  • the substrate carrying the magnetic head is provided with a recess in which the reinforcing layer of the one magnetic leg is accommodated. This recessed reinforcing layer does not reach as far as the pole end of the magnetic leg, but there is a predetermined distance to be measured in the vertical direction between it and this end.
  • the magnetic head which can be taken from the European patent application mentioned can be designed in such a way that the write function is essentially performed only with its leading magnetic leg, in particular according to the principle of vertical magnetization. That is, the magnetic head is supposed to write as a so-called single-pole head. Measures to be taken for this are known per se.
  • EP-A-0 232 505 shows a thin-film magnetic head whose magnetic legs are designed differently in terms of their magnetic behavior depending on the magnetic properties of the storage layer of a recording medium. A particularly steep writing field can be generated in this way due to the emphasis on the leading magnetic leg.
  • this magnetic head which can be found in the aforementioned EP-A, is also referred to as a "switching head". If you want the design features of this magnetic head on a magnetic head transferred with a recessed reinforcement layer, it can be seen that the magnetic properties of a recording medium to be assigned must be taken into account even further. However, details relating to this are not apparent from the European patent application mentioned.
  • the object of the present invention is therefore to design the data storage device of the type mentioned at the outset in such a way that its thin-film magnetic head is optimally adapted to a recording medium to be described and read out longitudinally or in particular vertically by it.
  • the maximum achievable field strength and the field gradient of the write flank of the head are chosen as high as possible and that a magnetic transition as vertical as possible with a very short transition length is written into the recording medium.
  • the vertical magnetic field generated by a non-saturated head, with which a magnetization pattern written into the recording medium is scanned should have the smallest possible spatial extent.
  • the storage layer of the recording medium is applied to an underlayer with a predetermined thickness D, measured perpendicular to the direction of movement, made of a soft magnetic material of predetermined saturation magnetization MS and that the following relationship applies:
  • MS which are saturation magnetization of this magnetic layer of the magnetic head.
  • * is the multiplication symbol.
  • the measures according to the invention are based on the knowledge that, in the case of a recording medium with a so-called double layer made of a soft magnetic base under a storage layer of this underlayer, crucial importance is attached to guiding the magnetic flux in the region of the pole ends of the head: From a head, which can be found in EP-A and is written as a single pole head, with a recording medium with a double layer, it can be seen that with this head a large part of the magnetic flux lies directly between the reinforcing layer of the leading magnetic leg and the trailing magnetic leg closes. Practically all field lines emerging from this reinforcement layer are absorbed directly by the magnetic layer of the trailing magnetic leg.
  • the magnetic field strength generated at the pole end of the leading magnetic leg, with which the recording medium is to be written, is reduced accordingly.
  • the magnetic properties and the (vertical) thickness of the soft magnetic base of the recording medium are consequently designed for the known magnetic head only for this reduced field strength.
  • the advantages of the measures according to the invention can now be seen in particular in the fact that the magnetic double layer of the recording medium is matched in terms of its geometric and magnetic parameters to the changed flow guidance of the magnetic head with an external reinforcement layer. Because of this coordination, relatively small write currents can advantageously produce a relatively strong write field of the leading magnetic leg, which has a steep flank.
  • pole height problem is alleviated.
  • the yield that can be achieved in head production depends primarily on the so-called pole height, i.e. from the vertical extension of the parts of the pole ends forming the two magnetic poles which run parallel to one another.
  • This pole height must be e.g. can be set as precisely as possible using a complex lapping process.
  • the pole height in the magnetic head of a data storage device according to the invention is much less critical.
  • Optimal flux guidance of the magnetic head of the data storage device according to the invention is specifically determined by the above-mentioned mathematical relationship in the special arrangement of the magnetic reinforcement layer of the leading magnetic leg on the outside of the guide body. Magnetic heads of the highest homogeneity with excellent read / write properties can be manufactured in this way.
  • FIG. 1 schematically indicates a data storage device according to the invention.
  • FIG. 2 shows, in a diagram, a write field strength to be generated by a magnetic head of the device according to FIG. 1 with a known recording medium.
  • FIGS. 3 to 8 pulse shapes to be obtained with a known data storage device are compared with those of a device according to the invention.
  • the writing field strengths to be obtained with a device according to the invention can be seen from the diagram in FIG.
  • FIG. 10 shows a further embodiment of a data storage device according to the invention.
  • the data storage device which is only partially illustrated in FIG. 1 as a longitudinal section and is generally designated 2, contains a magnetic head K with which data can be written into and read from a corresponding recording medium A, in particular according to the principle of vertical (vertical) magnetization.
  • the structure of this magnetic head largely corresponds to that of the magnetic head, which can be found in the European patent application mentioned at the beginning.
  • the magnetic head K is formed in thin film technology in layers on a substrate 3, which can be designed as a missile in a known manner and is not shown in the figure.
  • a non-magnetic material is advantageously used for the substrate. If this material should be electrically conductive, the substrate must also be provided with an insulation layer.
  • the missile and thus the magnetic head K are to be guided aerodynamically along a track relative to the recording medium A at a low flight altitude f.
  • This direction of movement, relative to the head, of the recording medium A, for example rotating under it, is indicated by an arrowed line denoted by v.
  • the recording medium A has a storage layer 4 which is adapted to the intended magnetization principle, for example made of a CoCr alloy, the thickness D of which is generally less than 1 ⁇ m, preferably less than 0.5 ⁇ m.
  • This storage layer 4 is deposited on a soft magnetic underlayer 5 of predetermined thickness D.
  • the magnetic head K has a magnetic flux-guiding, ring-head-like magnetic guide body 6 with two magnetic legs 7 and 8.
  • the magnetic leg 7 facing the substrate 3 is to be regarded as the leading leg with respect to the direction of movement v.
  • Each of the two magnetic legs contains at least one magnetic layer 7a and 8a, which each form a magnetic pole P1 and P2 on the pole ends 9 and 10 facing the recording medium A.
  • the longitudinal, ie to be measured in the direction of movement v, thicknesses of these magnetic layers 7a and 8a in the region of their pole ends 9 and 10 are denoted by D and D ", respectively.
  • D ⁇ greater than D 2 is advantageously selected, D, generally being less than 1 ⁇ m.
  • Each of the magnetic legs 7 and 8 is magnetically reinforced outside of the regions containing the pole ends 9 and 10 with an additional, relatively thick magnetic layer 7b or 8b.
  • the longitudinal thicknesses D, and D. of these reinforcement layers are greater than the thickness D, and D 2 of the respectively adjacent magnetic layer 7a and 8a and are generally several ⁇ m.
  • These additional reinforcement layers advantageously serve to reduce the magnetic resistance in the magnetic guide body 6 and are also used for the desired asymmetry of the field profile of the writing field of the head.
  • the two magnetic reinforcement layers 7b and 8b are advantageously arranged such that they are attached the outside of the magnetic guide body 6. They do not extend to the area of the respective magnetic pole Pl or P2, but end at (vertical) distances al or a2 from a plane E. which runs through the surfaces of the poles Pl and P2 and defines the underside of the magnetic head K The end of the reinforcing layer 7b of the leading magnetic leg 7 facing the plane forms a tip S.
  • the magnetic reinforcement layer 8b of the trailing magnetic leg 8 is withdrawn further than the magnetic reinforcement layer 7b of the leading magnetic leg 7. That is, the distance a2 of the reinforcement layer 8b from the plane E of the magnetic poles P1, P2 can be chosen larger than the corresponding distance al.
  • the position of the magnetic reinforcement layer 8b with respect to the plane E has only relatively little influence on the read-write properties of the head K. If the reinforcement layer 8b is preferred, the resolution of the head can possibly be slightly improved become.
  • the strength of the vertical magnetic field emerging at the magnetic pole P1 can be influenced by the position of the tip S of the magnetic reinforcement layer 7b facing the recording medium A or the size a of the vertical distance from the plane E. In general, it should be noted that lower values of al lead to higher field strength values. On the other hand, it must not be made too small in order to ensure at the tip 5 of the reinforcement layer 7b an at least largely transfer of the magnetic flux carried in this reinforcement layer to the adjacent magnetic layer 7a. From these points of view, values for a1 between 0.5 ⁇ m and 2 ⁇ m, preferably at most 1.5 ⁇ m, have proven to be favorable.
  • the magnetic reinforcement layer 7b can advantageously be located in a trough-like depression 12 of the substrate 3. This depression is worked into the substrate and filled with the reinforcement layer 7b in such a way that the surface of the reinforcement layer 7b facing the magnetic layer 7a lies at least approximately in a common plane with the non-recessed surface of the substrate.
  • the distance between the two magnetic legs 7 and 8 is widened with respect to the gap width g.
  • the magnetic layer 8a of the magnetic leg 8 which is rearward (trailing) with respect to the direction of movement v extends only in a region comprising the pole end 10 with a height h, which is also referred to as the pole height, parallel to the magnetic layer 7a of the front layer which has just been formed Magnet leg 7.
  • the part of the magnetic layer 8a adjoining this vertical region leads to a larger distance w with respect to the plane magnetic layer 7a.
  • the magnetic leg 8 is attached to the magnetic leg 7 in a known manner on the side facing away from the recording medium, so that the approximately annular head-like shape of the guide body 6 results.
  • At least one single-layer or multi-layer coil winding 15 extends through the intermediate space 14 thus present between the two magnetic legs 7 and 8 in the extended guide body region, with which both the writing and the reading function can be carried out. If necessary, separate windings must also be provided for this.
  • the coil winding 15 should have a predetermined electrical flow or ampere winding number N * I for the write function, where N is the number of turns of the winding and I is the current strength of the write current.
  • the entire magnetic guide body 6 is in general covered on its free outside with a hard, non-magnetic protective layer.
  • the magnetic head K of the data storage device 2 is also to be designed with the aid of measures known per se (cf. in particular EP-A-0 232 505) in such a way that the writing field generated at the magnetic pole P1 of its leading magnetic leg 7 is opposite the one to the magnetic field of opposite polarity caused by the magnetic pole P2 is so strongly emphasized that the magnetic head K essentially performs the write function only with the field of the magnetic pole P 1, that is to say a magnetic reversal in the storage layer 4. Because of the arrangement of the magnetic reinforcement layer 7b on the outside of the magnetic leg 7, the magnetic flux for the writing process caused by the coil winding 15 in the leading magnetic leg 7 can at least largely be concentrated on the area of its pole end 9.
  • the vertical writing field emerging at the magnetic pole P1 is correspondingly strong.
  • the underlying soft magnetic underlayer 5 with regard to its magnetic properties and its layer thickness D. must be adapted to the magnetic field entering it in the area of the magnetic pole P1 in such a way that it does not go into magnetic saturation and thus loses effectiveness. If, for a magnetic head according to FIG.
  • This head is said to slide over a known recording medium at a flight height f of approximately 0.1 ⁇ m.
  • This recording medium has a storage layer 4 made of CoCr with a thickness D of about 0.3 ⁇ .
  • This effect can be explained by the fact that with increasing N * I the soft magnetic underlayer 5 is driven more and more into magnetic saturation and is practically saturated at the value N * I ** 1.5 A.
  • the soft magnetic underlayer is practically ineffective.
  • the increase in magnetic saturation is associated with a repulsion of the field lines entering the lower layer. This has to
  • the invention provides that a material with such a saturation magnetization MS and a layer thickness D be selected for the lower layer 5. that the product D u * MS, in contrast to known double-layer plates, is at least 20%, preferably at least 50% larger than the product D, * MS * ,.
  • D, and MS- the longitudinal layer thickness provided for the leading magnetic leg 7 in the region of its pole end 9, or the saturation magnetization of the selected material.
  • the write amplitude can be increased even further by a higher layer thickness D or by a lower write current I in the coil winding 15.
  • the double-layer system comprising the storage layer 4 and the lower layer 5 of the recording medium A is particularly advantageous if one dispenses with extremely high linear bit densities and instead uses the high write fields to describe hard storage materials with large values H Q of the coercive field strength. Since both the read voltage and the signal-to-noise ratio are proportional to H, the track density can be increased and the storage capacity increased. With these measures, very high frequencies are also avoided, which make a downstream read / write channel more expensive and, due to the associated smaller bit shift windows, also make them more susceptible to interference. This is particularly advantageous if a connected computer, such as a PC or WS, is very high data rates (data rates of, for example, 3600 rpm and 64 kfci: approx. 50 Mbit / s; window size with RLL 2.7 code: approx. 5 ns) cannot be processed.
  • FIGS. 3 to 5 and 6 to 8 various pulse shapes occurring in data storage devices are each indicated as a diagram in arbitrary units. However, the same scale ratios are chosen for corresponding diagrams.
  • a magnetic head K and a recording medium A of the storage device 2 according to the invention are mutually coordinated, it must be taken into account that, with an increasing improvement in the writing amplitude and flank, the written magnetic transition in the storage layer 4 of the recording medium is always better aligned vertically.
  • FIGS. 3 to 5 are assigned to a known data storage device with a magnetic head designed according to EP-A-0 232 505, while the pulse shapes shown in FIGS.
  • FIGS. 3 and 6 show the magnetization M in a double-layer recording medium as a function of the longitudinal position x with respect to a central plane through an (air) gap.
  • FIGS. 4 and 7 show the vertical head fields H 1 which can be obtained with the respective head when reading out the recording media magnetized according to FIG. 3 or FIG. 6.
  • the read signals V to be obtained during this reading can be seen from FIGS. 5 and 8. If the magnetization ratios shown in FIGS. 3 and 6 are compared with one another, it can easily be seen that an asymmetrical magnetization transition (see FIG. 3) written with the known magnetic head is always anti- becomes more symmetrical (see FIG. 6).
  • the measures according to the invention advantageously lead to a slimmer (steeper) curve shape and to higher amplitudes.
  • the pulse shaping of the known magnetic head is carried out in such a way that the asymmetry of the magnetic transition is compensated for by an asymmetry of the vertical head field during reading (cf. FIG. 4) by magnetically favoring the pole of the leading magnetic leg. In this way, an at least largely antisymmetric read signal (see FIG. 5) can be obtained.
  • Corresponding pulse shaping also takes place in the magnetic head of the data storage device according to the invention (cf. FIGS. 6 to 8).
  • the symmetry of the reading signal required with the magnetic head K shown in FIG. 1 with simultaneous strong emphasis on the magnetic pole P 1 of the leading magnetic leg 7 can in particular take place in such a way that the magnetic layers 7a, 7b and optionally 8b from a high ⁇ flux material (with a high value of the saturation magnetization MS.), While at least the magnetic layer 8a of the trailing magnetic leg 8 is selected from a material with a lower value of the saturation magnetization MS 2 . Since the known high-flux materials generally have to be subjected to annealing in order to achieve the desired magnetic properties, it is particularly advantageous if only the layer 7a or only the layers 7a and 7b consist of the material with the very high MS, value, while the other layers have the lower MS 2 value. Materials whose MS, value is above 900 kA / m are considered in particular as high-flux materials. Some of these materials are listed in the table below.
  • materials are suitable for the magnetic layer 8a of the trailing magnetic leg 8 and possibly for its magnetic reinforcement layer 8b which have a significantly lower MS 2 value, which is in particular at most 800 kA / m.
  • Such a saturation magnetization has, for example, known NiFe alloys (such as "Permalloy").
  • a further emphasis on the writing field of the leading magnetic leg 7 can be achieved by choosing the thickness D 2 of the trailing magnetic leg 8 to be significantly smaller than the thickness D, of the leading magnetic leg. It is advantageous if D 2 ⁇ 0.9 * D ⁇ applies.
  • an underlayer 5 the highest possible value of the saturation magnetization MS and a sufficiently large thickness D.
  • Materials with a saturation magnetization MS of at least 900 kA / m are particularly suitable.
  • the product of these two sizes should preferably be above 0.4 A, ie the following should apply: MS U * D> 0.4 A.
  • the influence of the saturation magnetization MS of a soft magnetic underlayer on the strength of the writing field can also be seen from the diagram in FIG.
  • the vertical distance al (in ⁇ m) of the tip of the magnetic reinforcement layer of a writing magnetic leg is plotted in the abscissa direction and the vertical magnetic field H (in kA / m) generated on the magnetic pole of this leg is plotted.
  • the curves IV, V and VI shown in the diagram are based on an exemplary embodiment of a storage device according to FIG.
  • MS 2 800 kA / m.
  • the magnetic field H decreases with increasing distance a1 from the tip S of the magnetic reinforcement layer 7b largely independently of the saturation magnetization MS.
  • there is a very pronounced influence of the size of the saturation magnetization MS ⁇ j Accordingly, correspondingly high vertical writing fields can also be generated with soft magnetic materials with high saturation magnetization.
  • Deviating from the exemplary embodiment of a data storage device shown in FIG Measures can also be combined with a magnetic head that has an agneto-resistive sensor in its air gap.
  • a corresponding embodiment is indicated in FIG. 10, a representation corresponding to FIG. 1 being selected for this figure and parts corresponding to FIG. 1 being provided with the same reference numerals.
  • the magnetic head generally designated K ', contains, in a manner known per se, a magneto-resistive sensor 22 in its (air) gap 21 between the poles 9 and 10 of its magnetic legs 7 and 8.
  • a correspondingly arranged sensor is e.g. known from the "International Magnetic Conference (INTERMAG)", Hamburg (DE), April 9-13, 1984, contribution EP-11 by the authors G.S.Mowry et al: "Electrical Characteristics of Co parable Inductive and Magnetoresitive Thin Film Heads".
  • Suitable elements are e.g. from DE-OS 33 42 511.
  • the measures according to the invention should relate to data storage devices which operate on the principle of vertical magnetization.
  • the measures according to the invention are to be regarded as particularly advantageous with regard to this magnetization principle, but are not limited to this. It goes without saying that the use of the magnetic heads K and K 'with or without magneto-resistive sensor 22 is also of great advantage in the case of longitudinal recording because of the lack of pole height problems and the higher achievable write field strengths.

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  • Recording Or Reproducing By Magnetic Means (AREA)

Abstract

Un dispositif (2) de mémorisation de données comprend un support d'enregistrement (A) avec une couche de mémorisation (4), ainsi qu'une tête magnétique (K) ayant deux branches d'aimant (7, 8). Les branches d'aimant comprennent chacune un couche magnétique (7a, 8a) formant un pôle magnétique, ainsi qu'une couche d'amplification magnétique (7b, 8b) située en dehors de la zone polaire. Les couches d'amplification (7b, 8b) forment en outre des parties des faces extérieures de la tête (K). La tête (K) est conçue de façon à n'écrire qu'avec la branche d'aimant (7) d'attaque. La couche de mémorisation (4) est appliquée sur une couche inférieure magnétique douce (5) ayant une épaisseur Du et une saturation magnétique MSu, l'équation suivante s'appliquant: Du * MSu » 1,2 * D1 * MS1. D1 représente l'épaisseur et MS1 la saturation magnétique de la couche magnétique (7a) de la branche d'aimant d'attaque (7).
PCT/EP1990/000746 1989-06-28 1990-05-09 Dispositif a memoire magnetique avec support d'enregistrement et tete magnetique a couche mince WO1991000593A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEP89111791.3 1989-06-28
EP89111791 1989-06-28

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WO1991000593A1 true WO1991000593A1 (fr) 1991-01-10

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6666267B1 (en) 1997-11-15 2003-12-23 Brunel Oilfield Services (Uk) Limited Downhole tools
USD983231S1 (en) 2012-04-04 2023-04-11 Summit Casing Services, Llc Casing centralizer having spiral blades

Citations (6)

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Publication number Priority date Publication date Assignee Title
GB2006508A (en) * 1977-09-30 1979-05-02 Iwasaki S Magtenic recording media
JPS57158014A (en) * 1981-03-26 1982-09-29 Akio Otsubo Vertical magnetic recording medium
JPS57203209A (en) * 1982-04-13 1982-12-13 Canon Inc Magnetic recorder
JPS59135601A (ja) * 1983-01-20 1984-08-03 Matsushita Electric Ind Co Ltd 垂直磁気記録方法
JPS59221801A (ja) * 1983-05-30 1984-12-13 Matsushita Electric Ind Co Ltd 垂直磁気記録方法
DE3607501A1 (de) * 1985-03-07 1986-09-11 Victor Company Of Japan, Ltd., Yokohama, Kanagawa Quermagnetisierungsaufzeichnungs- und wiedergabeanordnung

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2006508A (en) * 1977-09-30 1979-05-02 Iwasaki S Magtenic recording media
JPS57158014A (en) * 1981-03-26 1982-09-29 Akio Otsubo Vertical magnetic recording medium
JPS57203209A (en) * 1982-04-13 1982-12-13 Canon Inc Magnetic recorder
JPS59135601A (ja) * 1983-01-20 1984-08-03 Matsushita Electric Ind Co Ltd 垂直磁気記録方法
JPS59221801A (ja) * 1983-05-30 1984-12-13 Matsushita Electric Ind Co Ltd 垂直磁気記録方法
DE3607501A1 (de) * 1985-03-07 1986-09-11 Victor Company Of Japan, Ltd., Yokohama, Kanagawa Quermagnetisierungsaufzeichnungs- und wiedergabeanordnung

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Title
I.E.E.E. TRANSACTIONS ON MAGNETICS vol. MAG22, no. 5, September 1986, NEW YORK, N.Y., USA Seiten 370 - 373; V. ZIEREN et al: "PROPERTIES OF ONE-SIDED PROBE HEADS ON DOUBLE-LAYER PERPENDICULAR RECORDING MEDIA" siehe Seite 370, linke Spalte, Absatz 2 siehe Seite 370, rechte Spalte, letzter Absatz Seite 371, rechte Spalte, Zeile 7; Figuren 1-5 *
PATENT ABSTRACTS OF JAPAN vol. 6, no. 262 (P-164)(1140) 21 Dezember 1982, & JP-A-57 158014 (AKIO OOTSUBO) 29 September 1982, siehe das ganze Dokument *
PATENT ABSTRACTS OF JAPAN vol. 7, no. 57 (P-181)(1202) 09 März 1983, & JP-A-57 203209 (CANON K.K.) 13 Dezember 1982, siehe das ganze Dokument *
PATENT ABSTRACTS OF JAPAN vol. 8, no. 269 (P-319)(1706) 08 Dezember 1984, & JP-A-59 135601 (MATSUSHITA DENKI SANGYO K.K.) 03 August 1984, siehe das ganze Dokument *
PATENT ABSTRACTS OF JAPAN vol. 9, no. 93 (P-351)(1816) 23 April 1985, & JP-A-59 221801 (MATSUSHITA DENKI SANGYO K.K.) 13 Dezember 1984, siehe das ganze Dokument *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6666267B1 (en) 1997-11-15 2003-12-23 Brunel Oilfield Services (Uk) Limited Downhole tools
USD983231S1 (en) 2012-04-04 2023-04-11 Summit Casing Services, Llc Casing centralizer having spiral blades

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