FR2502824A1 - MAGNETIC TRANSDUCER HEAD - Google Patents

Abstract

A. MAGNETIC TRANSDUCER HEAD. B. HEAD CHARACTERIZED IN THAT IT INCLUDES A MAIN POLE 2, ONE OR MORE AUXILIARY POLES 10, THE ASSEMBLY BEING SURROUNDED BY A WINDING 4, THE LENGTH L ACCORDING TO WHICH THE MAIN POLE 10 EXCEEDS THE AUXILIARY POLE (s) 10, THE THICKNESS A OF THE AUXILIARY POLES 10 AND THE THICKNESS B OF THE WINDING 4 ARE SUCH AS 0.55 A (B2) LA 2.4. C. THE INVENTION APPLIES TO MAGNETIC RECORDING HEADS.

Description

The present invention relates to a transmission head

  magnetic conductor and in particular a magnetic transducer head

  tick for the vertical magnetization recording mode

wedge or perpendicular.

  To record a high frequency signal (signal

  short wavelength) on a magnetic recording tape

  However, it is known that the so-called vertical or perpendicular recording mode of recording is more advantageous than the so-called longitudinal magnetization recording mode; the first recording mode uses a magnetization in a direction perpendicular to the main plane of the band

  magnetic recording while the second mode of recording

  really uses a love following a main plane of the

  magnetic tape. This stems from the fact that the field of

  in a magnetic layer of a recording tape.

  Magnetic recording is weaker in a perpendicular magnetization record when the wavelength of the recording signal becomes shorter as the own demagnetization field becomes larger for recording.

  in longitudinal magnetization mode.

  Different types of transducer heads are known

  magnets used for the magnet recording mode.

  tation. To make such a recording (or

  tation of the tape's magnetic recording layer

  magnetic) and ideally or perfectly in recording mode.

  vertical magnetization, the main component must be

  the magnetic field from the magnetic transducer head is as vertical as possible for

  magnetic recording device such as a tape.

  Figure 1 shows an example of a transducer head

  In this transducer, the magnetic head 2 is formed of a thin film of high permeability magnetic material such as permalloy, and an auxiliary magnetic pole 3 are arranged on either side of a

  magnetic recording medium 1, so as to oppose.

  A winding 4 is provided around the auxiliary magnetic pole 3.

  However, in this case, the magnetic head

  3 must be placed on the opposite side of the main magnetic pole 2 with respect to the magnetic recording medium and in the vicinity of the magnetic recording medium, which causes difficulties in assembly and processing.

  for example the loading of the magnetic recording medium

  1 between the main magnetic pole 2 and the magnetic pole

that auxiliary 3.

  To avoid these drawbacks, it has been proposed to use a magnetic recording medium 1 such as that of FIG. 2 which is formed of a non-magnetic base 5

  a layer of high permeability material 6, as well as a layer of

  magnetic recording tape 7 made on the layer

  material with high magnetic permeability 6. In this case,

  that a single-pole magnetic head h is formed of a thin film of soft magnetic material, and is placed opposite the magnetic recording layer 7 and that a signal is

  applied to the winding 4 provided around the pole 2 for recording

  signal, we get a recording sensitivity

  satisfactory and an excellent recording characteristic.

  The main magnetic pole 2 of the head of trans-

  Magnetic conductor h of this type is formed of a thin film of ferromagnetic material such as permalloy, an alloy of the Fe-APt-Si system, a Sendust alloy with a thickness of 0.5 to 3 microns. The winding 4 intended to "excite by magnetization, the main magnetic pole 2 formed of a film

  thin to know the winding of recording can be constituted

  killed by a thin-film winding adhered to an insulating film such as a SiO2 film, A Q203 # Si3N4 or the like provided in the vicinity of the upper portion of the magnetic thin film pole 2. Under these conditions, in order to effectively excite the main magnetic pole 2 by means of the winding 4, it is desirable that the front end of the winding 4 is placed in such a way as to be wound with the upper part. the main magnetic pole 2 facing the sliding surface of the magnetic recording medium 1. When the winding 4 is at the front end facing the sliding surface of the magnetic recording medium 1, the winding 4 is bypassed by the magnetic recording medium 1 if

  the magnetic recording layer 7 is conductive.

  Even if the surface of the magnetic recording layer is made of an insulating material, there is a significant risk of short-circuiting for the winding 4 since the winding is generally made of a relatively soft material such as copper , aluminum, silver, gold etc, and the winding may develop by causing short circuits between the turns under the effect of the friction of the

  magnetic recording medium. Likewise when the winding

  4 is very close to the magnetic recording medium 1 as described above, a magnetic field generated

  winding 4 is directly applied to the recording medium

  magnetic recording 1 in addition to the magnetic field of recordings

  applied by the main magnetic pole 2. The range or zone of the magnetic field generated by the winding 4 is

  spread so wide that the magnetic field of

  registration that is applied to the magnetic recording

  tick 1 is forced to spread out, which is an obstacle for a

  very high density recording.

  Such drawbacks can be avoided by moving the excitation winding 4 away from the end of the main pole

  2 turned towards the magnetic recording medium that is

  say by making a gap between the upper part of the excitation winding and the end of the main magnetic pole. Thanks to this spacing, contact can be avoided

  of the excitation winding and the recording medium

  very magnetic. In addition, the magnetic field generated by the excitation winding decreases abruptly on the support

  magnetic recording when the gap increases.

  On the other hand, if the excitation winding 4 is arranged so as to leave an interval with respect to the support

  magnetic recording, although the part of the magnetic pole

  main tick 2 around which is provided the winding 4 is strongly magnetized, the magnetization level at the end of the main magnetic pole 2 projecting from the portion surrounded by the winding 4, decreases rapidly. This essentially stems from the fact that the excitation winding 4 is made very tight around the main magnetic pole 2 and the diameter of the winding 4 is chosen to be relatively small.

  so that the magnetic field of winding decreases rapidly

  when one moves away from the end of the winding and the main magnetic pole 2 is formed of a thin film having reluctance and so on. Figure 3 shows the relationship between a point of the main magnetic pole 2 and the magnetic flux density By along the axis of the main magnetic pole; in this graph,

  the abscissae represent the position of the point in the direction

  y, that is to say the axis of the main magnetic pole 2 and the ordinates represent the magnetic flux density By following the direction y. The solid line 8 corresponds to the By distribution of the magnetic transducer head with a

  very tight excitation winding on the main magnetic pole

  cipal so that this pole is protruding from the upper part of the excitation winding, over a length of about 50 microns. The dotted curve 9 corresponds to the

  By magnetic flux density when the magnetic pole

  pal is excited by a parallel magnetic field instead of

  that of the excitation winding 4 provided on the pole.

  As it follows from curve 8, magnetization

  of the upper part of the main magnetic rod 2

  relative to the winding 4 decreases rapidly. By con-

  as shown in curve 9 in Figure 3, the magnetic pole

  main tick 2 is excited completely to its end by the parallel magnetic field. Thus it is desirable that the main magnetic pole 2 is excited according to the parallel magnetic field. To obtain such a parallel magnetic field, it is necessary to increase the diameter of the winding 4. Or if the diameter of the winding 4 is increased as described above, the performance of the recording is deteriorated.

  requires a large recording current.

  To avoid this drawback as shown in FIG. 4, an auxiliary core 10 is made of a highly permeable material that is placed so as to fix it on one or both sides of the main magnetic thin film pole 2 so that it is projecting from the main magnetic pole; in

  in other words, we have auxiliary nuclei distant from the sur-

  sliding face of the magnetic recording medium 1.

  In these circumstances, it is clear that the record yield

  is improved more than if the excitation winding 4 was provided near the end of the auxiliary core 10, also

  as close as possible to the top.

  The present invention aims to create a magnetic transducer head for vertical magnetization recording, ensuring a very efficient recording,

  to effectively magnetize a mono magnetic core

  polar. For this purpose, the invention relates to a magnetic transducer head with a main magnetic pole formed of a magnetic thin film material having a surface

  and opposite a magnetic recording medium

  at one end thereof an auxiliary magnetic core in the vicinity of the main surface of the magnetic material

  in thin film with a thickness in the direction perpendicular to

  on the main surface, one end of the magnetic nucleus

  auxiliary tick away from the end of the magnet pole.

  than a principal distance E, a winding being provided

  tower of the main magnetic pole and the magnetic core

  at the end of the auxiliary magnetic core, the

  rolling having a thickness b, a, b and t4 being chosen so that the magnitude (a + 2 -) / ú is not less than 0.55

and does not exceed 2.4.

  The present invention will be described in more detail with the aid of the accompanying drawings, in which: - Figures 1, 2 and 4 are respectively diagrams showing a magnetic transducer head according to the prior art for recording with vertical magnetization . - Figure 3 shows the relationship between the magnetic flux density of the main magnetic pole and a point of the pole. FIGS. 5, 6 and 10 are respectively

  diagrams giving examples of magnetic transducer heads

according to the invention.

  Figures 7, 8, 9 are graphs serving

to explain the invention.

  - Figures 11 to. 17 are diagrams of the manufacturing phases of the magnetic transducer head according to the invention.

  DESCRIPTION OF DIFFERENT PREFERENTIAL EMBODIMENTS

OF THE INVENTION:

  According to the invention, it has been established that in a magnetic transducer head having an auxiliary core, the amplitude of the recording magnetic field of the upper part of the main magnetic pole depends on the amplitude of the magnetic field of excitation. the upper part of the pole

  main magnetic that is to say, the amplitude of a ---

  magnetic field at the upper part of the main magnetic pole when the main magnetic pole is removed and instead there is only the auxiliary core surrounded by the winding. That's why to record in the way the

  more efficient the signal on the magnetic recording medium

  tick, it must be designed to generate the magnetic field

  the most intense at the top of the main magnetic pole

  when a predetermined current is applied to the winding

  of excitement. In general, as the diameter of the roll-

  As it increases, the attenuation of the magnetic field at a location remote from the winding on the central axis of the winding decreases. Moreover, the magnetic field on the main axis of the winding decreases when the diameter of the winding

  increases. It is thus necessary to envisage an assembly of

  bearing, the position of the coil on the core, the diameter

  winding etc. by a suitable choice to obtain a

  excitation magnetic field, maximum.

  Taking into account the considerations and explanations above, as well as various tests, it is proposed in the context of the invention to provide a magnetic transducer head having a very high recording efficiency

  for a record with vertical magnetization.

  The embodiments of the magnetic transducer head according to the invention will be described hereinafter with reference to FIG. 5 and the following figures in which the same references as those of FIGS. 1, 2 and 4 have been used for

designate the same elements.

  In these figures, the letter H applies to the whole

  the mounting of the magnetic transducer head according to the

vention.

  In the embodiment of the invention,

  example 5 or 6, we have a magnetic

  main tick 2 formed of a thin film magnetic material such as permalloy, Sendust alloy etc. with a thickness of 0.5 to 3 microns, which thickness is represented by the letter t in the figures. On both surfaces or on a surface of the main magnetic plate 2, one or more auxiliary cores 10 are tightly magnetized in a highly permeable material.

  such as Mn-Zn ferrite, Ni-Zn ferrite or the like.

  This auxiliary core 10 is arranged so that its upper part

  is in a position further back from the upper

  of the main magnetic pole 2 facing the surface

  slip of the magnetic recording medium (not shown

  felt), the main magnetic pole 2 sliding over a distance t. The winding 4 is provided on the auxiliary magnetic core 10 so as to surround both the auxiliary magnetic core 10 and the main magnetic pole 2 by taking it in the intermediate position. More specifically, the winding 4 is disposed on the auxiliary magnetic core as close as possible to the end of this auxiliary core so that its upper surface can coincide with the upper surface of the auxiliary magnetic core 10 which is then

  surrounded for example by a winding of a conductive cable.

  If the thickness of the auxiliary core is equal to a, that is to say the distance between the surface of the main magnetic pole against which the magnetic pole

  auxiliary and the inner surface of the winding; the thick-

  the winding 4 is equal to b. According to the invention, the dimensions _ a, b are chosen so that the expression (a + 1) / ú does not exceed 2, 4 without being less than 0.55 for practical dimensions of I of between 10 and 200. microns. The reason for choosing the distance t as indicated above is derived from Figures 7 and 8 in which

  the magnetic field in the axial direction to the upper part

  of the main magnetic pole 2 by varying the

  value of (a + 2bA, varies in the head of the magnetic transducer

  In FIGS. 7 and 8, the magnetic field is a relative value for a maximum value equal to 100%. According to FIG. 7, the curves 11, 12, 13 each correspond to the cases in which

  the positions of the upper parts of the magnetic core pairs

  auxiliary ticks 10 arranged symmetrically to surround the main magnetic pole 2 as in FIG. 5, are such that the distance t between the upper part of the magnetic pole

  2 and the auxiliary magnetic core 10 is respectively

  30 microns, 50 microns and 100 microns; in FIG. 8, the curves 14, 15, 16 correspond to the cases in which the position of the upper part of the auxiliary magnetic core 10 provided next to the main magnetic pole 2

  (Figure 6) is such that the distance t between the upper part

  of the main magnetic rod 2 and the auxiliary core 10

  respectively equal to 30 microns, 50 microns and 100 microns.

  In these circumstances, Figure 8 shows the distribution of the

  magnetic field in the case of a spacing d equal to the dis-

  in the absence of an auxiliary magnetic core.

  According to FIG. 7, the magnetic field is the

  more intense for (a + b) / ú which equals 1.3; the magnetic field

  tick decreases by about -2% (1%) compared to the maximum value for (a + b) / .t which is between 0.8 and 2.0; this magnetic field decreases by -4% (+ 2%) compared to the value

  maximum for (a + b) / e between 0.65 and 2.4.

  According to Figure 8, the magnetic field is the most intense for (a + b) / ú equal to 1.22; the field decreases by about -2% (+ 1%) of the maximum value for (a + h) / t between 0.7 and 2.0: this magnetic field decreases by -4% (2%) of the maximum value for (a + b) / i of between 0.55 and 2.42. Comparing the curves of FIG. 7 with those of FIG. 8, it can be seen that the tendency according to which the upper part of the main magnetic pin 2 acts on the magnetic field is practically equal on the one hand when the auxiliary magnetic core 10 is provided on both sides of the main magnetic plate 2 and when provided on one side according to the embodiments of Figures 5 and 6. Figures 7 and 8 show

  that the magnetic field at the top of the magnetic pole

  that principal 2 is effectively improved, if (a + 2-Z is between 0.55 and 2.4, which is why the range of

  variations of (a + b) / is chosen between 0.55 and 2.4.

  In the embodiment of FIG.

  that the auxiliary core 10 is provided on one side of the magnet pole.

  2, a magnetic field similar to the upper part of the main magnetic head 2 is measured when the

  distance d between the other side of the main magnetic head

  cipal 2 which carries no auxiliary core 10 and the inner surface of the winding 4 opposite, varies selectively according to Figure 9. In this case e is chosen equal to 50 microns, equal to 50 microns and b equal at 20 microns. In addition, the length

  c winding 4 is equal to 50 microns.

  It is clear from Figure 9 that the magnetic field at the top of the main magnetic pole

  2 is the largest for d> b. Thus when the magnet nucleus

  that auxiliary 10 is provided on one side of the main magnetic pole 2, it is interesting to choose the lengths d and b so as to satisfy the inequality d% b. The height of the winding 4 that is to say the dimension bearing the reference c in Figures 5 and 6 does not act so much on the efficiency of the recording. However, it is not interesting to have a height ú very important by

  compared to the thickness b, as this reduces the efficiency of the

  tration. Therefore, the value of the ratio c / b must be equal to or less than 5 and in particular lower than

at about 2 to 3.

  Although for the auxiliary core 10, the length a of the upper side surrounded by the winding 4 is chosen so that the ratio (a + 2 -) / t is between 0.55 and 2.4,

  the thickness of the back side beyond the part of the kernel

  surrounded by winding 4, can be increased to

  take into account the needs of mechanical resistance.

  FIG. 10 shows an example of such an embodiment with reinforcing elements 17 made of a non-magnetic material such as Zn ferrite, which are glued to the upper part of the auxiliary magnetic core.

  to surround the upper part of the main magnetic pole

cipal 2 and strengthen it.

  If the auxiliary core 10 is provided on one side of the main magnetic pole 2, the reinforcing element 17 provided on the side o is the auxiliary magnetic core 10 does not extend either backwards or downwards to make body with the main magnetic pole 2 and the winding 4 can be

  planned at the same time around the extension of the reinforcing element

  17 and the auxiliary magnetic core 10, on the other side

of the main magnetic pole 2.

  For example, the dimensions of the parts

  of the magnetic transducer head H whose structure

  ture is shown in Figure 10, are the following t equal to 100 microns, equal to 150 microns, b is equal to 50 microns,

c equals 1.5 mm.

  In addition the thickness of the rear part of the magnetic core

  auxiliary 10, which is important and corresponds to the reference

  Figure 10 may be equal to 1 mm, its length

  both the reference f may be equal to 4 mm.

  In this case, a record carrier can be used.

  very magnetic 1 having a layer of material 6 with strong

  meability on a layer of permalloy with a thickness of 0.5 micron and whose magnetic recording layer 7 is a

  layer of Co-Cr alloy with a thickness of 0.5 micron.

  An example of a method of manufacturing a magnetic transducer head according to the invention will be given in

  detail below using Figures 11 and following.

  According to Fig. 1, a composite body 30 is made by gluing a rectangular block of magnetic material 20 and a plate of a non-magnetic material 27. The block of magnetic material 20 may be a Mn-Zn ferrite or a N-ferrite. Zn; the block of non-magnetic material may be glass,

  a ceramic, a non-magnetic Zn ferrite etc. He is

  desirable that the magnetic material and the non-magnetic material have a similar coefficient of thermal expansion and for this reason it is preferable that the block

  20 and the non-magnetic plate 27 are respectively

  magnetic ferrite and non-magnetic ferrite

  than. The block of magnetic material 20 and the plate of non-magnetic material 27 can be joined by gluing using hot gluing of glass, sodium silicate or glue.

  organic such as an epoxy resin or a mineral glue.

  Then, the composite body 30 formed of the block of magnetic material 20 and the plate of non-magnetic material 27 is cut along the surfaces defined by the lines

  mixed lines mi, m2, m3 ... (figure 11) to obtain a set of

  ble of plates 31 each having a predetermined thickness

(Figure 12).

  According to FIG. 12, the main surface 31a corresponding to the magnetic material element 20 and the nonmagnetic material element 27 forming the plate 31 is polished

  to have a mirror-like finish. On this primary surface

  31a, an insulating layer 32 is produced, for example made of SiO.sub.2, Si.sub.3N.sub.4, A.sub.23 or the like, and on this layer a layer 22 of thin-film magnetic material is produced, for example permalloy, Sendust alloy, etc. a thickness of 0.5 to 3 microns by proceeding by evaporation under vacuum, projection

or the like.

  According to Fig. 13, the magnetic material thin film 22 is selectively removed using a photolithography technique to leave ribbed portions 22 ', 22 "which are parallel to one another and have a predetermined width and spacing. The portions between the thin film strips 22 ', 22 "are filled with a non-magnetic material 34 so that the surface is flush with the surface of the magnetic thin film strips. In addition, you can

  cover the set of materials such as SiO2, Si3N4 and Al2O3.

  According to FIG. 14, another plate element 31 'cut in the same composite body 30 as the previous plate element (FIG. 11) and which consists of a magnetic element 20 and a non-magnetic element 27 is prepared and its main surface 31a 'is polished in the same way to the finish of a mirror: according to FIG. 14, this main surface 31a' is fixed on the lateral surface of the plate element 30 on which are fixed the magnetic material 22 thin film and the non-magnetic layer 34 as in Figure 13. A cavity or notch 35 is made at

  in the main surface 31a 'of the

  31 'for example by chemical attack: we introduce

  glue 36 in this notch 35 to secure the elements

  plate members 31, 31 'to each other.

  Where appropriate, as shown in FIG. 15, the external surfaces of the two elements in the form of

  plates 31, 31 'on the side of the non-magnetic element 27, the thickness

  of these elements being lower than that of the

  other parts. As indicated by the dashed lines, n1, n2 -

  in Figure 15, the cut plates are cut into

  strip-shaped elements having thin-film-shaped magnetic material 22 ', 22 "and whose upper surfaces are ground or polished to form a sliding surface S for the magnetic recording medium (not shown

in Figure 16).

  It is thus possible to make a transducer head

  magnetic circuit H according to the invention, the magnetic pole of which

  The thin film clip 22 is made of a thin film magnetic material 22 to come flush with the sliding surface.

  S of the magnetic recording medium; the elements of

  Forcing 17 formed from the non-magnetic element 27 are arranged on both sides of the main magnetic pin 2 near its end and the auxiliary cores 10

  are in the vicinity of the upper end of the primary head.

  cipal; these auxiliary cores 10 are made using the magnetic recording element 20 and are behind

the reinforcing element 17.

  When the nonmagnetic material elements 34 are in the vicinity of the main magnetic element 2, the

  between the two reinforcing elements 17 on both sides of the main magnetic plate 2, abutting the surface

  of sliding 8 of the magnetic recording medium is generally

  rarely filled with non-magnetic material 34 so as to reduce the amount of glue introduced into this gap; in other words, the contacting surfaces of the sliding surface S of the magnetic recording medium, using glue, are decreased to be lower in the case where there is no non-magnetic material 34. thus the jamming of the head since considerably reduces the amount of glue that arrives at the sliding surface S. This magnetic transducer head H is provided with a winding 4 which surrounds the thin portion in a position which is more behind that the sliding surface S. In this case, even in the magnetic transducer head H thus achieved, one respects the relations of dimensions and structure

  between the different elements as indicated above.

  Likewise this magnetic transducer head H

  for example, as shown in FIG.

  head port 43 provided with orifices 41 to fix it to the drum.

  Rotary bur of a video recorder with conductive paths 42.

  Each terminal of the winding 4 of the magnetic transducer head

  H is electrically connected to each conductive path 41

for example by welding.

  As indicated above, in the transducer head

  According to the invention, although the winding 4 is further back than the sliding surface S.of the magnetic recording medium, the recording efficiency

is high.

  It is also obvious that one can obtain the

  same effect for a magnetic transducer head according to the

* vention forming part of an element transducer head

  multiple, with a set of main points 2.

Claims (2)

R E V E N D I C A T I 0 N S   1) Magnetic transducer head characterized in that it consists of a main magnetic pole (2) formed of a thin film magnetic material having a main surface, an end of this head (2) being turned towards the support magnetic recording device (1), an auxiliary magnetic core (10) being provided adjacent to the main surface of the thin-film magnetic material (2), and having a thickness (a) in the direction perpendicular to that main surface the end of the auxiliary magnetic core (10) being remote from the end of the main magnetic pin (2) by a distance (t), a winding (4) being provided around the main magnetic pole (2) and the core auxiliary magnet (10), and at the end of this auxiliary magnetic core (10),   the winding (4) has a thickness (b), the parameters (a, b.   being chosen so that the ratio (a + b) / Z is greater than   or equal to 0.55 and less than or equal to 2.4.   2) Magnetic transducer head according to the claim   1, characterized in that the main magnetic element (2) has on both sides an auxiliary magnetic core (10).   ) Magnetic transducer head according to the   1, characterized in that the main magnetic element (2) has on one side an auxiliary magnetic core (10),   the other side forming a non-magnetic gap whose is greater than (b).   ) Magnetic transducer head according to the   1, characterized in that the main magnetic pole (2) has on both sides of the non-magnetic material, at the surface facing the magnetic recording medium.   ) Magnetic transducer head according to the   1, characterized in that the auxiliary magnetic core (10) is constructed such that a portion remote from the surface facing the magnetic recording medium   (1), part around which there is no winding,   feels thicker than the other part with winding (4).