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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • 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
  • G11B5/17—Construction or disposition of windings
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/127—Structure or manufacture of heads, e.g. inductive
  • G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
  • G11B5/3109—Details
  • G11B5/313—Disposition of layers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/127—Structure or manufacture of heads, e.g. inductive
  • G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
  • G11B5/3176—Structure of heads comprising at least in the transducing gap regions two magnetic thin films disposed respectively at both sides of the gaps
  • G11B5/3179—Structure of heads comprising at least in the transducing gap regions two magnetic thin films disposed respectively at both sides of the gaps the films being mainly disposed in parallel planes
  • G11B5/3183—Structure of heads comprising at least in the transducing gap regions two magnetic thin films disposed respectively at both sides of the gaps the films being mainly disposed in parallel planes intersecting the gap plane, e.g. "horizontal head structure"
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
  • H01F17/06—Fixed inductances of the signal type with magnetic core with core substantially closed in itself, e.g. toroid
  • H01F17/062—Toroidal core with turns of coil around it
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/10—Composite arrangements of magnetic circuits
  • H01F3/14—Constrictions; Gaps, e.g. air-gaps
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
  • H01F41/30—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates for applying nanostructures, e.g. by molecular beam epitaxy [MBE]
  • H01F41/302—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates for applying nanostructures, e.g. by molecular beam epitaxy [MBE] for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices
  • H01F41/308—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates for applying nanostructures, e.g. by molecular beam epitaxy [MBE] for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices lift-off processes, e.g. ion milling, for trimming or patterning
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/32—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying conductive, insulating or magnetic material on a magnetic film, specially adapted for a thin magnetic film

Definitions

• the present invention relates to a method for increasing the operating frequency of a magnetic circuit and a corresponding magnetic circuit.
• inductive components typically inductors, either unitary or multiple, or forming part of a network of elementary components integrated on the same chip
• transformers magnetic field sensors or means for measuring a quantity linked to a magnetic field, magnetic recording heads, etc.
• inductive components inductive components (inductors, transformers, magnetic heads, etc.), it is advantageous to channel the magnetic flux by a magnetic circuit of high permeability, since this allows either a gain in performance at a given size, or a decrease in size for given performance.
• the magnetic circuits are generally made of solid ferrite whereas, in the integrated components, stacks of thin layers of ferromagnetic alloy (typically Fe-Ni) are more frequently used. and insulation.
• ferromagnetic alloy typically Fe-Ni
• the performance of the insulating / alloy composites in thin layers is much higher than that of the ferrite components and makes it possible to envisage operation at frequencies far beyond the radiofrequency domain.
• these materials have their own limitations, linked either to fundamental phenomena or to the technology used.
• Two limiting phenomena linked to technology are the skin effect and dimensional resonance. Both have the effect of reducing the effective permeability of the composite and altering its frequency response.
• the first can be avoided (or limited) conventionally by choosing a thickness of the magnetic layers of the stack significantly lower (or of the same order of magnitude) than the skin depth.
• the skin thickness is 0.2 ⁇ at 1 GHz for the Fe-Ni alloy.
• the second, linked to dimensional resonance, is associated with electromagnetic propagation within the composite in directions parallel to the layers. It can be limited, on the one hand, by keeping a sufficient thickness of insulation between the magnetic layers (to the detriment of the useful filling factor) and on the other hand by limiting the lateral dimensions of the magnetic circuits or of the cores. Thus, for a frequency of 1 GHz, the width of the FeNi magnetic circuit or core must be much less than 700 ⁇ m, a condition just compatible with a concern for integration. Another limitation, unrelated to technology and of a more fundamental nature, corresponds to the phenomenon of gyro agnetic resonance.
• the frequency of this resonance constitutes, in fact, an upper limit to the usable frequency domain, knowing that at frequencies below the resonance, the relative permeability is practically constant and equal to its static value. It is well known that, in an alloy of given composition, it is possible, by simple heat treatments, to vary the permeability and the resonance frequency. Thus, the limitation due to the gyromagnetic resonance is not expressed only in terms of frequency. We show, in fact,
• the term “increase in the operating frequency of a magnetic circuit” is understood to mean pushing back at a higher frequency at least the most limiting phenomenon, this phenomenon possibly being in particular gyromagnetic resonance, skin effect, dimensional resonance, etc.
• the invention recommends introducing into the circuit, cuts (or "intervals”, “interruptions”, “air gaps”, “grooves” or “gap” in English terminology), these cuts being perpendicular to the direction of the field, that is to say perpendicular to the mean line of the circuit.
• cuts will create a very demagnetizing field effective in the material.
• the magnetic permeability will be lowered without modifying either the overall shape of the circuit or the magnetic material. For example, in the case of magnetic recording heads (in which there is already at least one air gap), it is possible to add breaks in the rest of the circuit to increase the frequency withstand of the magnetic material.
• the present invention therefore relates to a method for increasing the operating frequency of a magnetic circuit, this method being characterized in that it consists in forming in at least part of this circuit, perpendicular cuts at the middle line of the magnetic circuit.
• the cuts are formed in parallel planes.
• periodic cuts are formed with a certain pitch and a certain thickness.
• the present invention also relates to a magnetic circuit, which is characterized in that it comprises, in at least one part, cuts perpendicular to the mean line of the magnetic circuit and arranged in parallel planes.
• these cuts are periodic.
• the invention has numerous advantages: a) It makes it possible to adapt the frequency range of use of a core or of a magnetic circuit, therefore of a component, while preserving the best possible permeability. In practice, it is possible, by keeping the same magnetic material, to choose a cut size and a spacing of the latter so that, in particular, the gyromagnetic resonance frequency and the other frequencies characteristics are adapted to the specifications of the component. Instead of changing either the magnetic material or the shape of the magnetic circuit for each desired frequency range, it is thus possible to have a wide range of possible frequencies for each pair (material, form of circuit). b) It is fully compatible with the circuit manufacturing processes. c) It does not change the macroscopic form of the component or of its magnetic circuit. d) It allows to keep the same magnetic material to create components with different operating frequencies.
• FIG. 1 shows the variations of the gyromagnetic resonance frequency f r as a function of the ratio e / p of the thickness (e) at the pitch (p) of the cuts;
• FIG. 4 shows an example of a magnetic circuit according to the invention, in the form of a torus;
• FIG. 5 shows another example of a magnetic circuit according to the invention adapted to a magnetic read head.
• Carrying out a magnetic layer interrupted periodically by thickness cuts (e) made in the direction of the mean line of the magnetic circuit with a spatial period (p), with a material having an intrinsic permeability ⁇ , of static value ⁇ s , amounts to to artificially create a layer of material of effective permeability ⁇ e , of static value ⁇ es , such that: l / ⁇ resort (l / ⁇ 3 ) + (e / p) When (e / p) increases, l / ⁇ es increases correspondingly which shows that ⁇ es decreases.
• the decrease in ⁇ e3 is accompanied by a correlative increase in the resonance frequency in accordance with the relation:
• FIG. 1 gives, for example, the variation of the cut-off frequency f c as a function of the ratio (e / p) for a composite of iron-nickel and silicon nitride.
• FIGS. 2a to 2e illustrate five steps of a method for producing a magnetic layer buried in a substrate.
• the magnetic layer is a branch of a magnetic circuit belonging to a vertical magnetic head with integrated coil as described in application FR-A-2 745 111.
• this magnetic layer is multilayer and the thicknesses of the different layers are not on the same scale in these figures.
• FIG. 2a a substrate 10
• FIG. 2b A thick layer 12, of several micrometers of insulator, for example silica, is deposited on this substrate.
• This layer 12 is then etched using a mask having periodically spaced openings.
• Fig. 2b boxes 14 separated by walls 16. The thickness of these defines the thickness of future cuts and their periodicity defines the pitch p of said future cuts.
• a sub-layer 20 is deposited on the assembly (FIG. 2c), for example by sputtering with Fe-Ni, and a mask of resin 22 is formed, leaving the area where the layer is to be made clear. magnetic interrupted by cuts.
• the magnetic layer 24 is then deposited (FIG. 2d) for example by electrolytic growth of FeNi from the sublayer 20.
• the resin is then delaciated, the assembly is optionally annealed and an insulating layer 26 is deposited, by example in Si 3 N.,.
• the stack thus obtained is then planarized by mechanical or chemical mechanical lapping (fig. 2e).
• a series of magnetic blocks 30 is then obtained, separated from each other by cuts 32.
• the first magnetic layer 24 is grown, for example electrolytically, from the sublayer 20 at a height sufficient to fill the boxes and then planarized as in FIG. 2e after delamination .
• FIG. 3a schematically illustrate another embodiment of the method of the invention.
• a substrate 40 for example made of silicon
• this substrate is covered with an insulating layer 42 (for example made of Si0 2 ).
• a stack of alternating layers (FIG. 3b), magnetic 44 and insulating 46 respectively, is then deposited.
• the magnetic layers can be deposited by sputtering.
• the insulating layers may be made of Si 3 N 4 and be arranged by sputtering.
• a resin mask 48 is then formed with openings 50.
• the cuts 52 are formed in the multilayer stack.
• this alternative embodiment can be used to form a single-layer magnetic material.
• FIG. 4 shows an example of a magnetic circuit according to the invention. It is a torus 60 whose mean line 62 is a circle. This circuit is provided with cuts 64 perpendicular to this mean line, therefore radial. The plane of these cuts rotates 360 ° as we travel the circuit. A winding 66 is also shown.
• FIG. 5 shows another example of a magnetic circuit and corresponds to a magnetic read head.
• This circuit 70 has a rounded rear part and two lateral branches approaching to delimit an air gap 72.
• the middle line 74 has a substantially circular shape at the rear and two branches approaching.
• the cuts 76 are perpendicular to this mean line.
• the circuit is completed by a conductive coil 78 and it is placed opposite a magnetic support 80 where magnetic information is written.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Power Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Nanotechnology (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Composite Materials (AREA)
• General Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Coils Or Transformers For Communication (AREA)
• Thin Magnetic Films (AREA)
• Soft Magnetic Materials (AREA)
• Manufacturing Cores, Coils, And Magnets (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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ID=9511576

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Cited By (3)

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Citations (2)

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• 1997
  • 1997-09-29 FR FR9712080A patent/FR2769122B1/fr not_active Expired - Fee Related
• 1998
  • 1998-09-22 US US09/508,692 patent/US6940383B2/en not_active Expired - Fee Related
  • 1998-09-28 DE DE69828073T patent/DE69828073T2/de not_active Expired - Lifetime
  • 1998-09-28 JP JP2000514294A patent/JP2001518702A/ja active Pending
  • 1998-09-28 WO PCT/FR1998/002069 patent/WO1999017319A1/fr not_active Ceased
  • 1998-09-28 EP EP98945384A patent/EP1019927B1/fr not_active Expired - Lifetime

Patent Citations (2)

Non-Patent Citations (1)

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