Source: http://www.google.com/patents/US6072667?dq=%22robert+sheehan%22
Timestamp: 2016-10-22 22:07:46
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Patent US6072667 - Method and apparatus for analysis of magnetic characteristics of magnetic ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA method and apparatus for analysis of magnetic characteristics of a magnetic device used for designing a magnetic head. The magnetic head has recording and reproducing characteristics and a recording and reproducing apparatus of magnetic characteristics. The apparatus for analysis of magnetic characteristics...http://www.google.com/patents/US6072667?utm_source=gb-gplus-sharePatent US6072667 - Method and apparatus for analysis of magnetic characteristics of magnetic device, magnetic head, and magnetic recording and reproducing apparatusAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS6072667 APublication typeGrantApplication numberUS 08/715,774Publication dateJun 6, 2000Filing dateSep 19, 1996Priority dateFeb 18, 1994Fee statusLapsedAlso published asUS5602473Publication number08715774, 715774, US 6072667 A, US 6072667A, US-A-6072667, US6072667 A, US6072667AInventorsYoshiaki Mizoh, Koichi Osano, Masaya SakaguchiOriginal AssigneeMatsushita Electric Industrial Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (10), Referenced by (2), Classifications (26), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMethod and apparatus for analysis of magnetic characteristics of magnetic device, magnetic head, and magnetic recording and reproducing apparatus
US 6072667 AAbstract
A method and apparatus for analysis of magnetic characteristics of a magnetic device used for designing a magnetic head. The magnetic head has recording and reproducing characteristics and a recording and reproducing apparatus of magnetic characteristics. The apparatus for analysis of magnetic characteristics includes a data input part, a coupled analysis part, and a result output part. The data input part is provided with data related to the characteristics of substances composing the magnetic device, data related to the magnetic device divided into a plurality of parts, data concerning the boundary conditions for analysis of the magnetic device, and data concerning the boundary conditions for analysis of the magnetic field. In the analysis part, a stress distribution for each of the plurality of parts divided on the basis of the data related to the boundary conditions input from the data input part is obtained, and magnetic characteristics for each of the plurality of parts based on the data concerning the boundary conditions of the magnetic field and the stress distribution of the magnetic device are obtained, and magnetic characteristics of the whole magnetic device are obtained based on the magnetic characteristics of each of the plurality of parts.
1. A magnetic head comprising a ring type magnetic head for sending and receiving signals with a magnetic medium,wherein the material comprising said ring type magnetic head includes at least ferrite, said ferrite having a negative magnetostriction constant, and a material having a smaller thermal expansion coefficient than that of said ferrite is attached on the side surface of said ring type magnetic head in a magnetic path on the side of the head being formed in gap depth direction, wherein a curve of magnetic flux density versus magnetic field strength in rubbing direction differs from a curve of magnetic flux density versus magnetic field strength in gap direction of said magnetic medium of substances comprising a magnetic circuit, and each substance has a higher curve of magnetic flux density versus magnetic field strength than at a time of no stress on said ring type magnetic head, and wherein initial permeability μ1 in rubbing direction and initial permeability μ2 in gap depth direction of said magnetic medium of substances comprising a magnetic circuit meet the following formula 1: 1.1&lt;&#956;1/&#956;2&lt;1.4                                        (formula 1). 2. A magnetic head comprising a ring type magnetic head for sending and receiving signals with a magnetic medium,wherein the material comprising said ring type magnetic head includes at least ferrite, said ferrite having a negative magnetostriction constant, and a material having a smaller thermal expansion coefficient than that of said ferrite is disposed on the back side of said ring type magnetic head a magnetic path on the side of the head being formed in gap depth direction, wherein a curve of magnetic flux density versus magnetic field strength in rubbing direction differs from a curve of magnetic flux density versus magnetic field strength in gap direction of said magnetic medium of substances comprising a magnetic circuit, and each substance has a higher curve of magnetic flux density versus magnetic field strength than at a time of no stress on said ring type magnetic head and wherein initial permeability μ3 in rubbing direction and initial permeability μ4 in zap depth direction of said magnetic medium of substances comprising a magnetic circuit meet the following formula 2: 1.1&lt;&#956;3/&#956;4&lt;1.4                                        (formula 2). Description
This invention relates to a magnetic recording equipment used for an audio equipment, a video equipment, an information equipment etc., or relates to a magnetic device such as a transformer and a coil. This invention further relates to a method and an apparatus for analysis of magnetic characteristics, a magnetic head, and a recording apparatus for the aforementioned equipments and devices.
As far as a video tape recorder (VTR) and a Digital Audio Tape (DAT) are concerned, a bulk type magnetic head 38 in FIG. 5 (a), a metal-in-gap type magnetic head 39 in FIG. 5 (b), and a laminate type magnetic head 40 in FIG. 5 (c) etc. are used. The bulk type magnetic head 38 shown in FIG. 5 (a) comprises at least a magnetic substance 42 such as ferrite, sendust, and permalloy which forms a magnetic path, a magnetic gap 41, and a non magnetic material 43 such as glass for fixing two cores of magnetic circuits 47, 48 which form the magnetic gap. The metal-in-gap type magnetic head 39 shown in FIG. 5 (b) comprises at least a high magnetic saturation substance 44 such as a metal film which forms a magnetic path in the vicinity of a magnetic gap, a magnetic substance 42 such as ferrite, sendust, permalloy etc. which forms the magnetic path besides the vicinity of the gap, a magnetic gap 41, and a non magnetic material 43. The laminate type magnetic head 40 shown in FIG. 5 (c) comprises at least a magnetic substance 45 forming a magnetic path, a magnetic gap 41, and a non magnetic material 46 such as ceramics for supporting the magnetic substance.
It is an objective of this invention is to solve the above-mentioned problems in the conventional methods by providing a method and an apparatus for analysis of magnetic characteristics of a magnetic device which are used for designing excellent magnetic heads. A further objective of this invention is to provide a magnetic head having excellent recording and reproducing characteristics. A further objective of this invention is to provide an excellent magnetic recording and reproducing apparatus.
A fifth configuration of the magnetic head of this invention comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein initial permeability μ1 at rubbing direction and initial permeability μ2 at gap depth direction of the magnetic medium of substances comprising a magnetic circuit meet the following equation 17: ##EQU3##
A sixth configuration of the magnetic head of this invention comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein at least ferrite is used at one part of a composite material comprising a magnetic circuit of the magnetic head, and initial permeability μ3 at rubbing direction and initial permeability μ4 at gap depth direction of the magnetic medium of the ferrite meet the following equation 18: ##EQU4##
A seventh configuration of the magnetic head of this invention comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein at least a material composing the head is a bonded ferrite of a single crystal ferrite and a polycrystal ferrite, and a rubbing side of the magnetic medium has initial permeability μ5 at rubbing direction of the magnetic medium with the single crystal ferrite, and the part which does not rub with the magnetic medium has initial permeability μ6 magnetically isotropic with the polycrystal ferrite, and permeabilities μ5 and μ6 meet the following equation 19: ##EQU5##
According to the fifth configuration of the magnetic head of this invention, the magnetic head comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein initial permeability μ1 at rubbing direction and initial permeability μ2 at gap depth direction of the magnetic medium of substances comprising a magnetic circuit meet the following equation 17: ##EQU6## As a result, a magnetic head having excellent output characteristics can be obtained.
According to the sixth configuration of the magnetic head of this invention, the magnetic head comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein at least ferrite is used at one part of a composite material comprising a magnetic circuit of the magnetic head, and initial permeability μ3 at rubbing direction and initial permeability μ4 at gap depth direction of the magnetic medium of the ferrite meet the following equation 18: ##EQU7## As a result, a magnetic head having excellent output characteristics can be obtained.
According to the seventh configuration of the magnetic head of this invention, the magnetic head comprises a ring type magnetic head for sending and receiving signals with a magnetic medium, wherein at least a material composing the head is a bonded ferrite of a single crystal ferrite and a polycrystal ferrite, and a rubbing side of the magnetic medium has initial permeability μ5 at rubbing direction of the magnetic medium with the single crystal ferrite, and the part which does not rub with the magnetic medium has initial permeability μ6 magnetically isotropic with the polycrystal ferrite, and permeabilities μ5 and μ6 meet the following equation 19: ##EQU8## As a result, a magnetic head having excellent output characteristics can be obtained.
FIG. 1 is a flow chart showing a first embodiment of a method for analysis of magnetic recording characteristics of this invention.
FIG. 8 is a view showing stress σx at x direction of initial permeability at x direction and dependency of stress σy at y direction.
This invention will be explained by referring to the following illustrative examples and attached figures. The examples are not intended to limit the invention in any way.
In the manufacturing process of a magnetic head, it is often so that an anneal step of about 200� C.˜700� C. is included in order to remove distortions etc. caused while processing a magnetic substance. Furthermore, in the step of achieving bonding by using a non magnetic material 43 and the like such as glass etc. which is shown in FIG. 5 or in other steps, adhesion is accomplished by heating at the temperature of about 400˜800� C. and pressurizing by an external force. Therefore, stress is given to the magnetic substance by thermal stress caused by the difference of thermal expansion coefficients of the composite materials or by external force, and a curve of magnetic flux. density--magnetic field strength changes through magnetostriction. Moreover, as shown in FIG. 5, since the magnetic head has a complicated form, the distribution of stress becomes complicated as well. As a result, the distribution of the curve of magnetic flux density--stress becomes complicated. Accordingly, it is necessary to make a tremendous effort for obtaining an optimum combination of initial permeability and form. It is effective to use an apparatus for analysis of magnetic characteristics in order to obtain this optimum combination of initial permeability and form, and also to obtain combinations of thermal expansion coefficients between the magnetic substances 42, 44, 45 etc. and the non magnetic materials 41, 43, 46 etc.
FIG. 1 is a flow chart showing a first embodiment of a method for analysis of magnetic recording characteristics of this invention. An apparatus for analysis of magnetic characteristics comprises a data input part 1, a coupled analysis part 2, and a result output part 3.
In the high frequency area of over 1 MHz, magnetic phenomena can be explained by the dynamic movement of an electron spin. The flow of magnetic flux within a magnetic body can be explained mainly by magnetization rotation. Frequency dependency of a magnetic moment at the time when the movement of the spin conducting precession is obstructed by a relaxation mechanism is know as Landau-Lifshitz equation and is shown as the equation 6 (Reference: Physics of Ferromagnetic Body, Author: Soushin Chikakado, Publisher: Shoukabou, 1984). ##EQU9## In the above-noted equation, θ represents a direction of the spin shown in FIG. 14, γ represents a gyro magnetic constant, μ0 =4πX 10-7. λ represents a damping frequency, and t represents time. The internal energy E is shown in the equation 7 as the sum of crystal magnetic energy, magnetostriction energy, and energy by the effective magnetic field Heff. ##EQU10## In the above-noted equation, K1 represents crystal magnetic energy, Heff represents a sum of an external magnetic field H 0 and a demagnetization field Hd. λ100 represents a magnetostriction constant at (100) direction, λ111 represents a magnetic constant at (111) direction, σ represents stress at i direction, Is represents saturation magnetization, i represents x, y, and z, αj represents a direction cosine formed between the magnetic field with the azimuth shown in FIG. 14 and the crystal orientation, and γji represents a direction cosine of stress at i direction.
By solving the equation 6, the magnetization mode within the magnetic body can be described. For example, when art external magnetic field is determined as an alternating current magnetic field shown as H0 =H1 ejωt, magnetic fluxφ (ω) within a microelement can be described as the equation 8. ##EQU11## In the above-noted equation, H1 represents a strength of the magnetic field of external alternating current, j represents an imaginary number, ω represents an angular velocity calculated by 4πx frequency, and ω0 represents a value shown as the equation 9. ##EQU12##
For obtaining a magnetic flux density of each element, a domain wall motion may be added to the equation 6. For example, the equation of motion with 180 degrees domain wall is shown as the equation 10 (Reference: Physics of Ferromagnetic Body, Author: Soushin Chikakado, Publisher: Shoukabou, 1984). ##EQU13## In the above-noted equation, m represents a mass of a domain wall per unit area, β180 represents a damping coefficient of the domain wall, s represents energy of the domain wall, and α represents a recovering force of the domain wall.
By solving the equations simultaneously in combination, instability of the solution caused by having a non-linear part or divergence of the solution can be avoided, so that the convergence solution can be obtained stably. As for each element k, when it is Ak (θk, Hk)=0 in the equations 1 to 4 and when the solutions of the equations 6 and 10 are shown as φk (θk, Hk)=0, θk, Hk which satisfy the both can be obtained in the following equation. ##EQU14##
FIG. 2 is a flow chart showing a second embodiment of a method for analysis of magnetic recording characteristics of this invention. An apparatus for analysis of magnetic recoding characteristics of this invention comprises a data input part 1, a serial analysis part 10 which conducts the analysis of the flow of magnetic flux density in each element and the analysis of magnetic characteristics in the entire magnetic device alternately, and a result output part 3.
The serial analysis part 10 comprises a stress analysis part 4, an initial value input part 14, a magnetic flux density calculating part 11, a matrix forming part 12, a solving part 13, and a convergence judgement part 7. First, in the stress analysis part 4, a stress distribution within the magnetic device is obtained based on the data input from the data input part 1, as in the first embodiment. In the initial value input part 14, an initial value of the effective magnetic field Heff is determined. Then, in the magnetic flux density calculating part 11, a magnetic field dependent curve of magnetic flux density for each element can be calculated by using the equations 6 and 10. Next, in the matrix forming part 12, magnetic characteristics of the entire magnetic device are described with the equations 1 to 4, and formulas for each element are formed by means of a method selected from the group consisting of a magnetoresistive method, a finite element method, a boundary element method, a finite difference method, a boundary integral method, an integral equation method, a surface charge method, a charge simulation method, a magnetic moment method. Thereafter, in the solving part 13, a magnetic flux density and a magnetic field distribution of each element can be obtained. By using the magnetic field distribution obtained in this way, the magnetic flux density of each element is obtained in a magnetic flux density calculating part 11, and the magnetic characteristics of the whole magnetic device are obtained in the matrix forming part 12. The convergence conditions of the solutions obtained by alternately calculating in the magnetic flux density calculating part 11 and in the matrix forming part 12 are judged, and when convergence took place, the convergence solutions are forwarded to the result output part 3.
FIG. 3 is a flow chart showing a third embodiment of a method for analysis of magnetic recording characteristics of this invention. An apparatus for analysis of magnetic recording characteristics of this invention comprises a data input part 1, a coupled analysis part 22 which conducts the analysis for obtaining the initial permeability of each element and the analysis of magnetic characteristics in the entire magnetic device in combination, and a result output part 3.
Assumed that the form is flat and the magnetization rotates within the plane as with a magnetic head, and when the equation 6 is solved under this assumption, the initial permeability due to a rotational magnetization can be shown as the equation 13 below. ##EQU15## In the above-noted equation, βrot represents a damping constant of a rotational magnetization.
&#956;(&#969;)=&#956;rot +&#956;180                   (equation 15)
FIG. 8 shows the stress σx at x direction of the initial permeability at the x direction and the dependency of stress σy at y direction obtained in the above-noted way with 10 MHz. An example of calculating frequency dependency of the initial permeability is shown in FIG. 12. In FIG. 12, a mark ∘ indicates whole initial permeability μ, a mark ♦ indicates initial permeability μrot due to rotational magnetization, and a mark ▴ indicates initial permeability μ180 due to a domain wall motion.
For example, the initial permeability can be described with a rotational magnetization moment only in a sufficiently low frequency area, and when the sliding direction is determined as (110) plane and the gap depth direciton as (100) plane, the equation 15 can be described in the simplified formula as shown below. ##EQU17## In the above-noted equation, K1 and K2 represent crystal magnetic energy, σx, σy, and σz respectively represents stress at sliding direction, stress at width direction, and stress at gap depth direction.
FIG. 4 is a flow chart showing a fourth embodiment of a method for analysis of magnetic recording characteristics of this invention. An apparatus for analysis of magnetic recording characteristics of this invention comprises a data input part 1, a serial analysis part 30 which alternately conducts calculation of initial permeability of each element and formation of matrix for the entire magnetic device, and a result output part 3.
The serial analysis part 30 comprises a stress analysis part 4, an initial value input part 14, initial permeability calculating part 31, a matrix forming part 32, a solving part 13, and a convergence judgement part 7. First, in the stress analysis part 4, a stress distribution within the magnetic device is obtained based on the boundary conditions input from the data input part 1. Next, in the initial value input part 14, an initial value of the effective magnetic field Heff is determined. Then, in the initial permeability calculating part 31, initial permeability of each element can be calculated by using the equations 13 and 15. Next, in the matrix forming part 32, magnetic characteristics of the entire magnetic device are described with the equations 1 to 4. Thereafter, by solving formulas for each element in the solving part 13 by means of at least one method selected from the group consisting of a magnetoresistive method, a finite element method, a boundary element method, a finite difference method, a boundary integral method, an integral equation method, a surface charge method, a charge simulation method, a magnetic moment method, a magnetic field distribution of each element can be obtained. By using the magnetic field distribution of solutions obtained in the above-noted way, the magnetic flux density of each element is obtained in initial permeability calculating part 31, and the magnetic characteristics for the whole magnetic device are obtained in the matrix forming part 12. The convergence conditions of the solutions obtained by alternately calculating in the initial permeability calculating part 31 and in the matrix forming part 12 are judged, and when convergence took place, the convergence solutions are forwarded to the result output part 3.
It is effective for the improvement of magnetic recording efficiency to impose stress on materials comprising a magnetic circuit by bonding substances having different thermal expansion coefficient with the material composing the head to one side or both sides of a ring type magnetic head, and to make the initial permeability to be higher than with the state without stress.
The above-noted method of analysis is also applicable when the difference of thermal expansion coefficient and external force etc. of the material are small so there is almost no stress.
FIG. 11 shows the results of conducting an analysis of the recording and reproducing characteristics by using initial permeability μ1 at rubbing direction 75 and initial permeability μ2 at gap depth direction 76 shown in FIG. 9. As shown in FIG. 11, in a ring type magnetic head 71 which sends and receives signals with a magnetic medium, and when the permeability at the tape rubbing direction 75 of a magnetic material 63 comprising the magnetic circuit is determined as μ1 and the permeability at gap depth direction 76 is determined as μ2 then, it becomes clear that the output characteristics are satisfactory in the area where μ1 /μ2 corresponds to the equation 17. ##EQU18##
As shown in FIG. 15, a bulk type magnetic head 111 is manufactured by using a single crystal ferrite, and when the permeability at rubbing side direction 115 is determined as μ3 and the permeability at gap depth direction 116 is determined as μ4, then, it becomes clear that it is satisfactory in the area where μ3 /μ4 corresponds to the equation 18. ##EQU19##
A bulk type magnetic head was manufactured by using a single crystal Mn-Zn ferrite having anisotropy in the initial permeability (Fe2 O3 =54%, MnO=27%, ZnO=19%, initial permeability at (100) direction=500, initial permeability at (110) direction =400). In other words, by using this single crystal Mn-Zn ferrite, a magnetic head having the (100) axis direction in the rubbing direction 75 and the (110) axis direction in the gap depth direction 76 was manufactured as shown in FIG. 9. Therefore, in this embodiment, μ1 was 500 and μ2 was 400. As a Comparative Example 1, a magnetic head having the (110) axis direction in the rubbing direction and the (100) axis direction at gap depth direction was manufactured. In the Comparative Example 1, μ1 was 400 and μ2 was 500. Furthermore, as a Comparative Example 2, a magnetic head using a polycrystal ferrite having the permeability of 450 was manufactured. In the Comparative Example 2, μ1 was 450 and μ2 was 450. These magnetic heads were installed in a video tape recorder of VHS system having the structure shown in FIG. 10, and the recording and reproducing characteristics were compared. As shown in FIG. 10, the VTR apparatus functions such that a magnetic head 81 is mounted to a magnetic head mounting window 82 disposed on a rotating drum 83, and a magnetic tape 62 is wound helically around a fixed drum 84 and a rotating drum 83. The signals which are input via a reproducing amplifier 87 and recorded by a magnetic head 81 are once again read out at the magnetic head 81, and the signals are output after amplifying the signals with the reproducing amplifier 87. When the above-mentioned recording and reproducing characteristics of the magnetic heads were compared by the relative amounts, this embodiment shown in FIG. 9 had +1dB, the Comparative Example 1 had -0.2dB, and the Comparative Example 2 had +0.3 dB. Therefore, in a ring type magnetic head which sends and receives signals with a magnetic medium, it is effective to design such that the permeability at the tape rubbing direction of a material comprising the magnetic circuit becomes higher than the permeability at gap depth direction.
Moreover, this embodiment shown in FIG. 15 had μ3 /μ4 =1.25, whereas the Comparative Example 1 had μ3 /μ4 =0.8 and the Comparative Example 2 was μ3 /μ4 =1.0. As a result, the calculation results proved that this embodiment had higher output characteristics than that of the Comparative Examples 1 and 2.
Furthermore, in a ring type magnetic head 111 which sends and receives signals with a magnetic medium as shown in FIG. 15, at least the material composing the head comprises a bonded ferrite bonding a single crystal ferrite 113 and a polycrystal ferrite 112, and when the tape rubbing surface has the permeability μ5 at tape rubbing direction 115 with the single crystal ferrite 113 and has the magnetically isotropic permeability μ6 with the polycrystal ferrite 112, it becomes clear that the magnetic head is constructed to fulfill the following equation: ##EQU20## In this embodiment, it was explained by referring to the bulk type magnetic head 38 shown in FIG. 5 (a), but it goes without saying that the same effects can be attained by using a metal-in-gap type magnetic head 39 shown in FIG. 5 (b), and a laminate type magnetic head 40 shown in FIG. 5 (b).
FIG. 10 is a schematic view showing an example of a magnetic recording and reproducing apparatus of this invention. shows a tenth embodiment of this invention. In FIG. 10, 81 represents a magnetic head optimized by the above-mentioned analysis apparatus of magnetic characteristics of this invention, 82 represents a magnetic head mounting window, 83 represents a rotating drum 83, 84 represents a fixed drum, 62 represents a magnetic tape, and 86 represents a tape running direction. The above-mentioned ring type magnetic head having different permeabilities at tape rubbing direction and at gap depth direction in FIG. 10 is installed to the head mounting window 82 disposed on the rotating drum 83. The magnetic recording and reproducing are conducted by the relative movement of the magnetic head 81 and the magnetic tape 62. In this way, a magnetic recording apparatus having high recording and reproducing characteristics can be obtained. Although this embodiment referred to an upper drum rotating system such as VTR of VHS system, 8 mm VTR system, and DAT, it goes without saying that this invention can be also used for the D2 system etc. having a middle drum rotating system, an audio cassette recorder having a fixed pass system, or for magnetic heads such as a hard disc and a floppy disc. By using a magnetic head optimized by the above-noted apparatus for analysis of magnetic recording characteristics, it is considered as being possible to greatly improve the characteristics of the magnetic recording and reproducing apparatus.
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