JP2009259365A - Perpendicular magnetic recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase both recording magnetic field intensity and gradient, and also reduce the recording magnetic field leakage to the adjacent tracks to achieve high density recording when using a perpendicular magnetic recording head. <P>SOLUTION: The perpendicular magnetic recording head 1 has a recording head 10 and a reproducing head 30, and the recording head 10 has a main magnetic pole 11 and a magnetic-shield 15 formed on and around the main magnetic pole 11. The magnetic-shield 15 has a layered structure of a plurality of soft magnetic layers each different in saturation magnetic flux density. In this layered structure, a first soft magnetic layer 13 relatively high in saturation magnetic flux density is arranged at the main magnetic pole side, a second soft magnetic layer 14 relatively low in saturation magnetic flux density is arranged on it, and a third soft magnetic layer 12 relatively high in saturation magnetic flux density is arranged further on it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic head for a magnetic disk device, and more particularly to a perpendicular magnetic recording head suitable for recording high-density magnetic information on a medium surface.

  A semiconductor memory and a magnetic memory are mainly used for a storage (recording) device of information equipment. A semiconductor memory is used for the internal storage device from the viewpoint of access time, and a magnetic disk device is used for the external storage device from the viewpoint of large capacity and non-volatility. The storage capacity is an important index representing the performance of the magnetic disk device, and a large-capacity and small-sized magnetic disk device is required from the market with the development of the information society in recent years. A recording method suitable for this requirement is a perpendicular recording method. Since the magnetization direction of the recording medium of the perpendicular recording system is perpendicular to the medium surface, the influence of the demagnetizing field acting between adjacent magnetic domains is smaller than that of the longitudinal recording system. Therefore, high-density magnetic information can be recorded on a medium, and a large-capacity magnetic disk can be configured. Since this method can increase the density, it is considered that this method will become the mainstream in place of the conventional longitudinal recording method.

  In the perpendicular recording system, in order to realize high density recording, it is necessary to make the gradient of the recording magnetic field generated from the main pole steep. Patent Document 1 discloses a perpendicular recording magnetic head provided with a magnetic shield having soft magnetic characteristics on the trailing side with respect to the main magnetic pole as means for steepening the recording magnetic field gradient. In this magnetic head, in order to further steepen the recording magnetic field gradient, the distance between the main magnetic pole and the magnetic shield may be narrowed and a high saturation magnetic flux density material may be applied to the magnetic shield. However, when the distance between the main magnetic pole and the high saturation magnetic flux density magnetic shield is reduced, it means that a large amount of magnetic flux flows from the main magnetic pole to the magnetic shield, which is an obstacle to obtaining a strong recording magnetic field.

  In Patent Document 2, in a perpendicular magnetic recording head device composed of a main magnetic pole layer and a return path layer stacked with a nonmagnetic insulating layer interposed therebetween, in order to improve a recording magnetic field, it is far from the main magnetic pole. A return path layer is disclosed that forms a low saturation flux density layer of material having a lower saturation flux density than the side.

US Pat. No. 4,656,546 JP 2007-172707 A

  FIG. 19 shows the calculation results of the effective magnetic field (magnetic field with in-plane components) and magnetic field gradient in a single-layer magnetic shield and a magnetic shield in which soft magnetic layers having different saturation magnetic flux densities are stacked. The horizontal axis of the graph indicates the effective magnetic field (Heff_T.C.) At the center of the recording head, and the vertical axis indicates the value of the magnetic field gradient (dHeff_T.C.) That determines the magnetization transition width, which is an index of high-density recording. Table 2 shows representative values read from the graph. The upper part A of the table shows the result of configuring the magnetic shield as a single layer (thickness 200 nm) with a saturation magnetic flux density of 1.68T. The middle stage B is a result of a configuration in which a layer with a low saturation magnetic flux density of 1.0 T having a thickness of 20 nm is laminated below, and a layer with a saturation magnetic flux density of 1.68 T having a thickness of 180 nm is laminated thereon. The lower stage C will be described later. In all the calculation results, the magnetic gap (Trailing Gap) between the main pole and the magnetic shield is fixed at 30 nm.

  Focusing on the calculation results, it can be seen that a strong magnetic field is obtained when a low saturation magnetic flux density film of B is arranged on the main pole side for both the magnetic field strength Hymax (vertical component magnetic field) and the effective magnetic field strength Heffmax. However, when compared with the field gradient that determines the magnetization transition of the recording medium (compared with the magnetic field gradient at 8 KOe of the dynamic coercive force of a typical perpendicular magnetic recording medium currently commercialized), the low saturation flux In the case of B in which a density layer is arranged, it is 206 KOe / um, which is lower than that of 227 KOe / um of A having a single layer structure.

  In order to realize high density recording, it is necessary to increase both the recording magnetic field strength and the magnetic field gradient. Furthermore, it is necessary to reduce the bleeding of the recording magnetic field to the adjacent track.

  An object of the present invention is to maintain a strong recording magnetic field from a main magnetic pole and make a magnetic field gradient steep in a perpendicular magnetic recording head.

  Another object of the present invention is to keep the recording magnetic field from the main pole strong in the perpendicular magnetic recording head, steep the magnetic field gradient, and reduce the bleeding of the recording magnetic field to the adjacent track.

A perpendicular magnetic recording head according to a first aspect of the present invention includes a main magnetic pole, a first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main magnetic pole, and the first magnetic layer on the opposite side of the air bearing surface. A second magnetic layer magnetically connected to the layer, a coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer; A magnetic shield provided via a magnetic layer,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities. A first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main magnetic pole side, and a periphery of the first soft magnetic layer. A second soft magnetic layer having a relatively low saturation magnetic flux density formed; and a third soft magnetic layer having a relatively high saturation magnetic flux density formed around the second soft magnetic layer.
In the perpendicular magnetic recording head, the thickness of the second soft magnetic layer is configured to be larger than the minimum length of the magnetic shield in the depth direction.

A perpendicular magnetic recording head according to a second aspect of the present invention includes a main magnetic pole, a first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main magnetic pole, and the first magnetic layer on the opposite side of the air bearing surface. A second magnetic layer magnetically connected to the layer, a coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer, and a nonmagnetic layer on the trailing side of the main magnetic pole A magnetic shield provided via,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities, and includes a first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main pole, and an upper surface of the first soft magnetic layer. A second soft magnetic layer having a relatively low saturation magnetic flux density formed on the second soft magnetic layer, and a third soft magnetic layer having a relatively high saturation magnetic flux density formed on the second soft magnetic layer.
Also in the second aspect, the thickness of the second soft magnetic layer is configured to be larger than the minimum length of the magnetic shield in the depth direction.

A perpendicular magnetic recording head according to a third aspect of the present invention includes a main magnetic pole, a first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main magnetic pole, and the first magnetic layer on the opposite side of the air bearing surface. A second magnetic layer magnetically connected to the layer, a coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer; A magnetic shield provided via a magnetic layer,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities. A first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main magnetic pole side, and a periphery of the first soft magnetic layer. A formed soft magnetic layer having a relatively low saturation magnetic flux density and having a thickness in a portion close to the main pole smaller than that of the other portion, and an upper portion of the second soft magnetic layer; And a third soft magnetic layer having a relatively high saturation magnetic flux density formed.
Also in the third aspect of the invention, the film thickness of the second soft magnetic layer is configured to be larger than the minimum length of the magnetic shield in the depth direction.

  According to the present invention, the recording magnetic field from the main magnetic pole can be kept strong and the magnetic field gradient can be made steep. Further, the bleeding of the recording magnetic field to the adjacent track can be reduced.

  FIG. 2 shows the basic configuration of a magnetic disk device using the perpendicular recording system. FIG. 2A is a plan view of the apparatus, and FIG. The recording medium 2 (in reality, there are a plurality of media 2-1 to 2-4) is directly connected to the motor 3 and is rotated when information is input / output. The perpendicular magnetic recording head 1 is held by a suspension 8, and the suspension 8 is supported by a rotary actuator 4 via an arm 7. The suspension 8 has a function of holding the perpendicular magnetic recording head 1 on the recording medium 2 with a predetermined force. Processing of the reproduction signal and input / output of information are performed by a signal processing circuit 5 and a recording / reproduction circuit 6 attached to the apparatus main body. Unlike the Lorentz waveform seen in the longitudinal recording method, the playback waveform (change in the amplitude of the playback signal with respect to the time axis) obtained by the perpendicular magnetic recording method is a trapezoidal wave, so the signal processing circuit and waveform equivalent circuit are in-plane magnetism. It is different from the recording method.

  The perpendicular recording system uses a medium having an easy axis of magnetization in the direction perpendicular to the recording surface. A glass or aluminum substrate is used for the recording medium 2 of the magnetic disk device. A magnetic thin film for forming a recording layer is formed on the substrate. A recording magnetic field from the main magnetic pole of the perpendicular magnetic recording head 1 acts on the recording medium 2 to reverse the magnetization of the recording layer. In perpendicular magnetic recording, since it is necessary to perform recording using the magnetic field component in the perpendicular direction, an under soft magnetic layer (SUL: soft under layer) is provided between the recording layer and the substrate.

  In order to write magnetic information on such a recording medium 2, a recording head that performs electromagnetic conversion is used. In order to reproduce magnetic information, a reproducing head using a magnetoresistance phenomenon, a giant magnetoresistance phenomenon, or an electromagnetic induction phenomenon is used. These recording head and reproducing head are provided in an input / output component called a slider, and become a perpendicular magnetic recording head 1. The perpendicular magnetic recording head 1 moves on the surface of the recording medium 2 along with the rotation of the rotary actuator 4 and is positioned at an arbitrary location, and then writes or reproduces magnetic information. An electric circuit for controlling this is present together with the signal processing circuit 5.

<Example 1>
The configuration of the perpendicular magnetic recording head 1 according to the first embodiment will be described. FIG. 1 is an enlarged view of a main part constituting the recording head. 1A is a view as seen from the air bearing surface facing the recording medium, and FIG. 1B is a cross-sectional view taken along the line XX of FIG. 1A, and is a cross-sectional view at the center of the main magnetic pole 11. . The main magnetic pole 11 extends to the air bearing surface 9, and the cross section has an inverted trapezoid. A magnetic shield 15 is provided above the main magnetic pole 11 (trailing side) via a nonmagnetic layer 19-1 and on both sides via a nonmagnetic layer 19-2. The magnetic shield 15 has a laminated structure of soft magnetic layers having different saturation magnetic flux densities, and a soft magnetic layer (first soft magnetic layer) 13 having a high saturation magnetic flux density is provided in the vicinity of the main magnetic pole 11 and is relatively surrounded by the surroundings. A soft magnetic layer (second soft magnetic layer) 14 having a low saturation magnetic flux density is provided, and a soft magnetic layer (third soft magnetic layer) 12 having a relatively high saturation magnetic flux density is provided around the second soft magnetic layer 14. Is provided. The recording track width is defined by the upper part (trailing side edge) of the main magnetic pole 11. Here, the length dS of the magnetic shield 15 in the depth direction is 100 nm in this embodiment. The film thickness of the first soft magnetic layer 13 is 20 nm, the film thickness (t-S1) of the second soft magnetic layer 14 is 200 nm, and the film thickness (t-S2) of the third soft magnetic layer 12 is 800 nm. The film thickness of the first soft magnetic layer 13 is set sufficiently smaller than the film thickness of the second soft magnetic layer 14. The saturation magnetic flux density of the second soft magnetic layer 14 is set lower than that of the third soft magnetic layer 12. This shield configuration is particularly for the purpose of suppressing the spread of the magnetic field in the track width direction and for steepening the gradient of the recording magnetic field. It should be readily understood that the first soft magnetic layer 13 can also serve as a plating seed film when forming a magnetic shield. FIG. 1B also shows a state in which the coil 18-2 for inducing a magnetic flux to the main magnetic pole 11 is arranged via the nonmagnetic layer 19-3.

  FIG. 3 shows a cross-sectional view of the perpendicular magnetic recording head 1 including the main part. The recording head 10 and the reproducing head 30 are formed on a slider substrate 31. The reproducing head 30 basically includes an insulating layer (underlayer) 32 provided on a slider substrate 31, a lower shield 33, an upper shield 35, and a reproducing element 34 that detects magnetic information.

  The recording head 10 is separated from the reproducing head 30 by the nonmagnetic layer 36. As already shown in FIG. 1, the first soft magnetic layer 13, the second soft magnetic layer 14, and the third soft magnetic layer are provided on the three sides of the main magnetic pole 11 via the nonmagnetic layer 19-1 and the nonmagnetic layer 19-2. Layer 12 is present. The first soft magnetic layer 13, the second soft magnetic film 14, and the third soft magnetic film 12 are magnetically connected, and are also magnetically connected to an upper magnetic layer (second magnetic layer) 17 for forming a closed magnetic path. The The second magnetic layer 17 is magnetically connected to the lower magnetic layer (first magnetic layer) 16 at the rear end, and the first magnetic layer 16 and the main magnetic pole 11 are magnetically connected. A coil 18-2 is arranged in a closed magnetic path composed of these. A third magnetic layer 42 is provided in parallel with the second soft magnetic layer 17 for the purpose of efficiently introducing a magnetic flux into the main magnetic pole 11. Further, a coil 18-1 is provided between the third magnetic layer 42 and the first magnetic layer 16. For the purpose of ensuring electrical insulation between the coil and the magnetic layer, the insulation layers 23, 21-1, 21-2 and 19-3 are arranged, so that a predetermined current is supplied to the coils 18-1 and 18-2. It can flow. An alumina layer can be used as the insulating layers 23, 21-1, and 21-2, and a polymer resin layer can be used as the insulating layer 19-3. For the purpose of protecting all the element parts described above, an alumina layer having a thickness of 25 μm is deposited as the nonmagnetic and insulating protective layer 24.

  When a current flows through the coil 18-2, the magnetic flux is guided from the second magnetic layer 17 to the main magnetic pole 11 through the first magnetic layer 16. At the same time, when a current flows through the coil 18-1, the lower magnetic flux is guided from the third magnetic layer 42 to the main magnetic pole 11 through the recording medium. Any magnetic flux has a function of strengthening the recording magnetic field generated from the main magnetic pole 11, but the flow of the magnetic flux at the bottom toward the paper surface has a function of weakening the influence of the recording magnetic field on the reproducing element 34.

  Here, the magnetic air gap 19-1 between the first soft magnetic layer 13 and the main magnetic pole 11 determines the amount by which a part of the magnetic flux generated from the main magnetic pole 11 is returned to the second soft magnetic layer 14. And has a function of increasing the gradient of the recording magnetic field.

  In this embodiment, a NiFeCo alloy having a saturation magnetic flux density of 2.4 T is used as the main magnetic pole 11. The film thickness was approximately 160 nm. For the first soft magnetic layer 13, a NiFeCo alloy having a saturation magnetic flux density of 2.28 T and a thickness of 20 nm was used. As the second soft magnetic layer 14, a NiFe alloy having a saturation magnetic flux density of 1.68T having a thickness of 200 nm was used. For the third soft magnetic layer 12, a NiFeCo alloy having a thickness of 800 T and a saturation magnetic flux density of 2.4 T was used. As the first magnetic layer 16, a NiFe-based alloy having a film thickness of 1.2 μm was used. For the second magnetic layer 17, a NiFe-based alloy having a film thickness of 1.0 m was used. For the coils 18-1 and 18-2, copper having a film thickness of 2 μm was used.

  Next, the reason why a strong recording magnetic field and a high magnetic field gradient can be achieved in the above embodiment will be described with reference to FIG. FIG. 4 (a) is based on a shield configuration in which a third soft magnetic layer 12 having a relatively high saturation magnetic flux density is laminated on a second soft magnetic layer 14 having a relatively low saturation magnetic flux density. The calculation results of the effective magnetic field and magnetic field gradient when the first soft magnetic layer 13 having a relatively thin (20 nm) and relatively high saturation magnetic flux density is inserted are shown. FIG. 4B shows the calculation result as a numerical value. The calculation is based on the case where the first soft magnetic layer 13 having a relatively high saturation magnetic flux density is inserted: A, the case where a soft magnetic layer having a relatively low saturation magnetic flux density is inserted: C, and the case where neither is inserted: B A total of three types were conducted.

  4A, the horizontal axis Heff_T.C. Represents the value of the effective magnetic field at the center of the recording head, and the vertical axis dHeff_T.C. Represents the value of the head magnetic field gradient. FIG. 4B shows the maximum effective magnetic field value of the recording head: Heffmax and the magnetic field gradient value dHeffmaxTrackCenter at an effective magnetic field of 8 KOe. Focusing on the results, it can be seen that the magnetic field gradient is higher in the case A where the first soft magnetic layer 13 having a high saturation magnetic flux density is inserted than in the case B where the first soft magnetic layer 13 is not inserted. This tendency is remarkable as compared with the case C in which a soft magnetic layer having a low saturation magnetic flux density is inserted, and can be said to be an effect of inserting the first soft magnetic layer 13 having a high saturation magnetic flux density on the main magnetic pole side.

  In comparison with the simple two-layer configuration shown in FIG. 19B, in FIG. 19B, the case B in which a soft magnetic layer having a relatively low saturation magnetic flux density is inserted under the soft magnetic layer. Thus, a higher magnetic field strength is obtained compared to case C in which a soft magnetic layer having a relatively high saturation magnetic flux density is inserted under the soft magnetic layer. In contrast, in the first embodiment (the case of FIG. 4A), the soft magnetic layer 12 having a high saturation magnetic flux density is provided in a portion far from the main magnetic pole 11, and as a result, a relatively high magnetic field strength is obtained. You can see that it is obtained.

  Thus, according to the first embodiment, a high magnetic field gradient can be obtained by providing the first soft magnetic layer 13 having a relatively high saturation magnetic flux density on the main magnetic pole side. Furthermore, the magnetic field strength can be prevented from deteriorating by setting the film thickness to be thin. Further, the soft magnetic layer 12 having a relatively high saturation magnetic flux density is thickly provided in a portion far from the main magnetic pole, thereby preventing the magnetic field strength from deteriorating.

  Next, in order to verify the above effect, the configuration of the second soft magnetic layer 14 and the third soft magnetic layer 12 will be described with reference to FIGS. 5 and 6. Figure 5 shows an inverted trapezoidal main pole (flare point 80nm) with a geometric track width (Tww) of 80nm and film thickness (t-Tww) of 160nm in the depth direction via a gap of 35nm (nonmagnetic layer 19-1). This is a result of calculating the magnetic field strength of a case where a shield having a length (dS) of 100 nm is arranged. The magnetic field strength also depends on the recording medium conditions. For this calculation, a saturation magnetic flux density of 1.35 T and a film thickness of 35 nm were assumed as the soft under layer (SUL) of the recording medium. The magnetic distance (hm) between the recording layer and the main pole was 11 nm.

  The calculation was performed for shields with different material configurations (saturated magnetic flux density materials). Specifically, A: 1.0T, B: 2.0T, C: 2.28T single layer configuration (the second soft magnetic layer 14 and the third soft magnetic layer 12 shown in FIG. Is 1 um), and in contrast to the configuration of the first embodiment, a high saturation magnetic flux density soft magnetic layer 14 (2.28 T, film thickness t-S1 is 200 nm) on the main pole side, and a low saturation magnetic flux density at a far site. The four cases of D in which the soft magnetic layer 12 (1.0 T, film thickness t-S2 is 800 nm) were arranged. In the graph shown in FIG. 5, the horizontal axis indicates the magnetic field strength (indicated by the effective magnetic field applied to the recording medium), and the vertical axis indicates the magnetic field gradient at each magnetic field strength point. Further, the values of the maximum magnetic field strength (Heffmax) and the maximum magnetic field gradient (dHeffmax) are shown in a table on the lower right side of the figure.

  Focusing on the results, it can be seen that in the case of a single layer film, the maximum magnetic field gradient increases as the saturation magnetic flux density increases, but the maximum magnetic field strength decreases. On the other hand, in the configuration in which the high saturation magnetic flux density layer is disposed on the main magnetic pole side, the maximum magnetic field strength is increased, but the maximum magnetic field gradient is decreased. This result shows that experience from the in-plane magnetic recording head cannot be applied to the perpendicular magnetic recording head.

  FIG. 6 shows that the thickness of the second soft magnetic layer 14 is made thicker (t-S1: 200 nm) than the length in the depth direction (dS: 100 nm), and the saturation magnetic flux density is set in the third soft magnetic layer 12. This is a calculation result of a lower configuration. Specifically, the saturation magnetic flux density of the third soft magnetic layer 12 was kept constant at 2.4T, and the saturation magnetic flux density of the second soft magnetic layer 14 was set at 2.28T and 1.68T. Focusing on the results, it can be seen that a high magnetic field gradient of 245 Oe / nm or more and a recording magnetic field strength of 10.1 KOe or more are obtained in any case. Incidentally, when the result of setting the saturation magnetic flux density of the second soft magnetic layer 14 to 2.28 T and the calculation result assuming the single-layer film of 2.28 T shown in FIG. It can be seen that a high magnetic field gradient is obtained. In particular, when the saturation magnetic flux density of the second soft magnetic layer 14 is reduced to 1.68 T, it can be seen that a stronger magnetic field strength is obtained without reducing the magnetic field gradient so much.

  Next, the soft magnetic layer 14 having a relatively low saturation magnetic flux density is inserted into a position sandwiched between the soft magnetic layers 13 and 12 having a high saturation magnetic flux density, and the film thickness (t-S1) is increased in the depth direction. The reason why the spread of the magnetic field distribution can be suppressed by setting the thickness thicker than the thickness (dS) will be described. FIG. 7 shows a calculation result when the thickness of the second soft magnetic layer 14 having a low saturation magnetic flux density (t-S1: indicated as Thickness TS_lower in the table) is changed in the range of 30 nm to 400 nm. In this calculation, the saturation magnetic flux density (1.68 T) and the length in the depth direction (d-S) of the second soft magnetic layer 14 having a low saturation magnetic flux density were fixed to 100 nm. The saturation magnetic flux density of the third soft magnetic layer 12 far from the main magnetic pole constituting the shield is fixed at 2.4T, and the total film thickness including the thickness of the second soft magnetic layer 14 having a low saturation magnetic flux density is 1 μm (adjusted with a film thickness of t-S2; excluded from this study because the magnetic field strength significantly deteriorated under the condition of t-S2 <t-S1). In addition, the same conditions as the previous calculation results were assumed for the main magnetic pole, the recording medium, and the flying height.

  Focusing on the calculation results, it can be seen that the maximum effective magnetic field strength (Heffmax_TrackCenter) takes a maximum value at t-S1 = 100 nm. However, deterioration at a film thickness t-S1 beyond that is small. On the other hand, it can be seen that the magnetic field gradient (dHeff_at_Heff8KOe) at 8 KOe assuming the recording magnetic field of the medium is smaller as the t-S1 becomes thicker, but shows a tendency to deteriorate.

  8 and 9 show the above calculation results in the track width direction (0 on the horizontal axis means the track center). In particular, FIG. 9 is an enlarged view of FIG. 8 to be compared. This magnetic field distribution is important for evaluating the bleeding phenomenon of the recording magnetic field on the adjacent track. That is, a narrow magnetic field intensity when viewed in the track width direction means that there is less blur. 8 and 9 from this point of view, it can be seen that the thinner the t-S1 (denoted as t_TSlower in the figure), the stronger the bleed magnetic field in the region far from the track center and the deterioration.

  This calculation was performed for the case where the geometric track width of the main pole was 80 nm. Since the recording magnetic field extends beyond the geometric width, the track pitch is practically set to about 90 to 100 nm (actually depends on the medium characteristics). Therefore, the influence of the recording magnetic field applied to the adjacent track must consider the range of 135 nm (90/2 + 90) to 150 nm (100/2 + 100). From this point of view, it can be said that it is ideal because the difference becomes small when t-S1> 100 nm or more.

  Incidentally, in this calculation, it is assumed that dS = 100 nm, so satisfying t-S1> dS satisfies the ideal magnetic field environment (more specifically, t-S2> t-S1> dS). It can be said. On the other hand, when t-S1 is as thin as 30 nm, it exceeds the normalized magnetic field of 0.42 over a wide range, and accumulation when adjacent tracks are recorded many times becomes a problem. That is, there is a high possibility that the quality of adjacent magnetic information deteriorates due to the multiple recordings allowed within the product life of the magnetic recording apparatus. For this reason, there is a problem that the reliability is inferior to the requirement that the magnetic recording device is nonvolatile.

  The fact that the distribution of the recording magnetic field deteriorates is a problem similar to the deterioration of the magnetic field gradient already described. In the first embodiment, considering that the recording magnetic field and the magnetic field gradient are slightly deteriorated when t-S1 is increased, the condition of t-S1> dS having an excellent magnetic field distribution is obtained for the purpose of narrowing the track. It is suitable for a highly reliable high track density recording head.

  If the magnetic field distribution is further referred to, there is a difference in the recording direction distribution. This will be described with reference to FIG. This figure shows the magnetic field distribution in the recording direction of the previous calculation result. In the horizontal axis, the trailing edge of the main pole is zero. The vertical axis represents the effective recording magnetic field (absolute value with in-plane components added). Focusing on the results, there is little difference in magnetic field strength in the vicinity of the main pole. However, a slight peak is seen around 0.035um. This peak position coincides with the 35 nm gap (nonmagnetic film 19-1) position provided between the main pole and the magnetic shield. Therefore, this peak is a magnetic field distribution due to the magnetic charge generated at the end of the magnetic shield (having a negative polarity because it is a magnetic charge due to the return magnetic flux). As the magnetic field in this portion increases, the signal quality deteriorates because a negative magnetic field is applied to the magnetization transition after recording. Looking at the calculation results from this point, it is clear that the magnetic field distribution at the same site deteriorates as t-S1 (denoted as t_TSlower in the figure) becomes thinner. It can be seen that the distribution can be minimized under the condition t-S1> d-S in Example 1. From this point of view, it can be said that the condition t-S1> d-S is suitable for a high-density recording head.

  The reason why the magnetic field distribution is excellent under the t-S1> d-S condition is considered to be due to the geometric factor. That is, the magnetization direction of the same part should be substantially parallel to the air bearing surface (medium surface). Shields belonging to the class of the present invention are composed of magnetic layers having different saturation magnetic flux densities, but magnetic charges are generated at the joints due to differences in saturation magnetic flux densities. Under the condition t-S1 <d-S, the film thickness t-S1 in the direction in which the magnetic flux leaks is thinner than the width d-S in the direction in which the magnetic flux flows. For this reason, the demagnetizing field in the flow direction of the magnetic flux becomes remarkable, and as a result, the magnetic flux easily flows in the t-S1 direction which is the longitudinal direction. As a result, the distribution is considered to deteriorate.

  This effect is consistent even when the thickness of the nonmagnetic layer 19-2 provided on both sides of the main pole (side gap length: distance between the shield and the main pole as viewed in the track width direction) is changed. It is confirmed from the calculation. As a more extreme example, it has been confirmed that the same result can be obtained even when the side gap length described below as Example 2 is assumed to be infinite (a structure without a side shield part).

  From the above, the saturation magnetic flux density of the third soft magnetic layer 12 is set higher than the saturation magnetic flux density of the second soft magnetic layer 14, and the film thickness t-S1 of the second soft magnetic layer 14 is set to the length dS in the depth direction. The need to set a larger thickness is understood.

As described above, according to the first embodiment, the blur magnetic field in the track width direction is minimized and an excellent magnetic field distribution in the recording track direction is realized while satisfying the high recording magnetic field and the high magnetic field gradient. be able to. From this effect, a magnetic disk device having high-density recording with a recording density of 375 Gb / in ² can be realized.

  In the first embodiment, the perpendicular magnetic recording head having the recording head and the reproducing head has been described as an example, but it goes without saying that the perpendicular magnetic recording head having only the recording head may be used.

<Example 2>
The configuration of the perpendicular magnetic recording head according to the second embodiment will be described with reference to FIG. 11 is an enlarged view of the main part constituting the recording head as in FIG. 1, FIG. 11 (a) is a view seen from the air bearing surface, and FIG. 11 (b) is YY in FIG. 11 (a). FIG. 3 is a cross-sectional view taken along the line and cut at the center of the main pole 11. The difference from FIG. 1 is that shields 15 ′ are not arranged on both sides of the main magnetic pole 11. Other configurations are the same as those of the first embodiment. The magnetic shield 15 ′ is composed of a laminated structure of soft magnetic layers having different saturation magnetic flux densities, and a soft magnetic layer (first soft magnetic layer) 13 having a high saturation magnetic flux density is provided in the vicinity of the main magnetic pole 11, on which is provided. A soft magnetic layer (second soft magnetic layer) 14 having a relatively low saturation magnetic flux density is provided, and a soft magnetic layer (third soft magnetic layer) having a relatively high saturation magnetic flux density is provided on the second soft magnetic layer 14. 12 is provided. In this configuration, a soft magnetic layer serving as a shield is not disposed on both sides of the main magnetic pole 11.

  Even in this configuration, a first soft magnetic layer 13 having a high saturation magnetic flux density is disposed at a portion approaching the main magnetic pole 11, and a second soft magnetic film 14 is laminated thereon, and the second soft magnetic film 14 is disposed in the depth direction. The film thickness (t-S1) is thicker than the length dS. The saturation magnetic flux density of the second soft magnetic film 14 is lower than that of the third soft magnetic film 12 laminated thereon. As a result, a high magnetic field gradient and a strong recording magnetic field strength can be obtained as in the first embodiment.

  In FIG. 12, a first soft magnetic layer 13 having a high saturation magnetic flux density (1.9 T, 20 nm) is disposed on the main magnetic pole side, and a third soft magnetic layer 12 having a saturation magnetic flux density of 2.4 T (fixed to a film thickness of 800 nm) is disposed on the shield. The magnetic field gradient when the saturation magnetic flux density of the intermediate second soft magnetic layer 14 is changed in the range of 1.68 T to 2.24 T (film thickness 200 nm) is obtained. The magnetic field gradient was obtained assuming a dynamic coercivity of 8 KOe of the recording medium. In this calculation, when a single layer film is used for the shield (denoted as TS gradient in the figure, the saturation magnetic flux density is the same as that of the first soft magnetic layer 13) and the configuration of Example 2 (denoted as laminating TS gradient in the figure) Are comparing. When attention is paid to the results, the single layer film (TS) of any one of the saturation magnetic flux density conditions (with the saturation magnetic flux density of the soft magnetic layer 12 being 2.4 T and the saturation magnetic flux density of the soft magnetic layer 14 being lower) It can be seen that a higher magnetic field gradient is obtained with the laminating example 2 than the results. In particular, the difference becomes significant under the condition where the saturation magnetic flux density of the second soft magnetic layer 14 is increased. This is presumably because the effective magnetic field gradient at 8 KOe in which the magnetic field gradient is obtained is lowered because the magnetic field strength is greatly reduced in the single-layer film configuration.

From this result, it can be understood that a high magnetic field gradient and a strong magnetic field strength can be satisfied even in a configuration (TS structure) in which a magnetic shield is provided only on the upper part (trailing side) of the main magnetic pole. Further, the spread of the magnetic field distribution can be suppressed by setting the film thickness (t-S1) of the second soft magnetic layer 14 to be thicker than the length (dS) in the depth direction. The main part cross section of the main magnetic pole vicinity of a modification is shown. Also in this modification, the first soft magnetic layer 13 having a high saturation magnetic flux density is disposed on the main magnetic pole 11 side, the second soft magnetic layer 14-1 having a relatively low saturation magnetic flux density is disposed thereon, and further The third soft magnetic layer 12-1 having a high saturation magnetic flux density is disposed thereon. Further, the film thickness t-S1 is set thicker than the length dS in the depth direction of the second soft magnetic layer 14-1 having a low saturation magnetic flux density. However, as shown in the figure, the length in the depth direction of the third soft magnetic layer 12-1 increases as the distance from the main magnetic pole 11 increases. In this configuration, a magnetic field gradient higher than that obtained by simply increasing the saturation magnetic flux density of the third soft magnetic layer 12-1 was obtained. This effect is considered to be an effect that the efficiency of the magnetic flux passing through the third soft magnetic layer 12-1 is promoted by having a shape spread. Even in this case, by reducing the thickness t-S1 of the second soft magnetic layer 14-1 having a low saturation magnetic flux density compared to the width dS in the magnetic flux flow direction, the influence of the demagnetizing field generated in the same portion is reduced. Can do. It goes without saying that the intended magnetic field distribution can be obtained.

  It is obvious that the same effect can be obtained by means of increasing the saturation magnetic flux density in multiple steps in the direction away from the main pole as long as t-S1> d-S is satisfied. In addition, in a region that is sufficiently long in the depth direction (or a region that extends in the width direction), the passage of magnetic flux does not become an obstacle, so even if a low saturation magnetic flux density material is applied to this part, it does not become an obstacle to the implementation. That is, as long as a magnetic flux flowing into the shield in the vicinity of the main pole is narrowed with a low saturation magnetic flux density material and thereafter a configuration that does not hinder the passage of magnetic flux (high saturation magnetic flux density material or geometrical expansion) is used, It is obvious that the above effect can be obtained.

  FIG. 14 shows a cross section of the main part in the vicinity of the main pole of another modification of the second embodiment. As shown in FIG. 14, the second soft magnetic film 14-2 having a relatively low saturation magnetic flux density located on the main magnetic pole 11 side also has the main magnetic pole 11 in the depth direction in the same manner as the third soft magnetic film 12-2. By increasing the distance from the distance, the flow of magnetic flux can be made more efficient. Even in this case, in consideration of the geometric demagnetizing field, it is necessary to satisfy t-S1> minimum d-S. In this configuration, the highest magnetic field gradient was obtained compared to the above-described embodiments and modifications. The magnetic field gradient is an index for determining the recording limit in the bit direction in magnetic recording, and it goes without saying that the higher the magnetic field gradient, the higher the density of the magnetic disk device can be realized.

  This configuration is relatively high with respect to the length in the depth direction of the soft magnetic layer 14-2 having a relatively low saturation magnetic flux density provided close to the main magnetic pole 11, and is continuously laminated on the soft magnetic layer. The soft magnetic layer 12-2 having the saturation magnetic flux density has at least a region where the length in the depth direction is longer than the vicinity of the main pole. As a technique for continuously changing the length of the shield film in the depth direction, it is easy to provide an inclination at the edge of the resist pattern as a mask when the soft magnetic layer is formed (the plating method is generally used). Can be formed.

  Another modification of the second embodiment is shown in FIG. 15 (cross-sectional configuration of the main part). A feature of this configuration is that a cutout (reduction in film thickness) is provided on the upper surface of the main magnetic pole 11 toward the air bearing surface 98. Further, a nonmagnetic layer 19-4 is newly disposed at a position above the main magnetic pole 11 and receded from the air bearing surface 98, and the second soft magnetic layer 14 together with the nonmagnetic layer 19-1 is formed of the nonmagnetic film 19-4. It is provided through a part. This configuration can generate a strong magnetic field from the point that the magnetic pole of the main magnetic pole 11 is three-dimensionally (constricted in the film thickness direction as well as in the width direction). Further, the rear end edge of the second soft magnetic layer 14 runs over the nonmagnetic film 19-4. For this reason, since the distance from the main magnetic pole 11 at the same portion is effectively increased, the magnetic flux flowing into the magnetic shield in the vicinity of the main magnetic pole 11 is further reduced compared to the above-described modification. For this reason, a high magnetic field gradient can be obtained. Even in this configuration, by satisfying t-S1> minimum dS on the air bearing surface side, the flow of magnetic flux in the soft magnetic layer portion with a low saturation magnetic flux density becomes ideal, and the desired excellent magnetic field distribution is obtained. I can do it. The definition of the depth length is the shorter of the length to the edge of the nonmagnetic film 19-4 or the flat region length formed above the main magnetic pole. This is considered to be because the function of the shield is exhibited only in the above-mentioned length region due to the effect that the magnetic flux concentrates on the air bearing surface side by providing the nonmagnetic film 19-4.

  As described above, the first embodiment, the second embodiment, and the modified examples have been described. However, the high saturation of the second soft magnetic layer 14 provided close to the main magnetic pole is continuously stacked on the soft magnetic layer 14. Setting the thickness of the soft magnetic layer 12 having a magnetic flux density large is effective in keeping the magnetic field strength high. Incidentally, the film thickness of the second soft magnetic film 14 is preferably in the range of 200 nm to 400 nm, and the film thickness of the third soft magnetic layer 12 is preferably 500 nm or more.

  In the above embodiments and modifications, the plating seed layer (electrode) when the magnetic shield is formed by the plating method is composed of a soft magnetic layer having a relatively high saturation magnetic flux density, thereby preventing deterioration of the magnetic field strength. In addition, it is for the purpose of preventing leakage of magnetic flux. As an effect thereof, the high magnetic field gradient and the spread of the recording magnetic field in the track width direction can be suppressed. This is a result of the magnetic flux being narrowed by a soft magnetic layer having a relatively low saturation magnetic flux density disposed on the plating seed layer. When a soft magnetic layer having a low saturation magnetic flux density is disposed on the seed layer, It can be easily understood that the magnetic field gradient is reduced as a result of the magnetic flux being constricted in the seed layer. Therefore, assuming that the seed layer does not hinder the flow of magnetic flux, the saturation magnetic flux density of the seed layer can be set to at least the same or relatively higher than the soft magnetic layer having a relatively low saturation magnetic flux density. is necessary.

  The magnetic shield can be formed by sputtering as well as plating. In this case as well, a soft magnetic layer having a relatively high saturation magnetic flux density and then a soft magnetism having a relatively low saturation magnetic flux density are formed on the main pole side. By sequentially laminating layers and a soft magnetic layer having a relatively high saturation magnetic flux density, it is possible to obtain the same effect as in the above-described embodiments and modifications.

  In addition, although the said modification was demonstrated as a modification of Example 2, it can also be set as the modification of Example 1. FIG. Even in this case, the same effect as described above can be obtained.

  Next, still another modification of the second embodiment will be described with reference to FIG. As is apparent from the figure, this modification is characterized in that the film thickness in the stacking direction of the soft magnetic layer 14 having a relatively low saturation magnetic flux density changes with respect to the track width direction of the main pole 11. . Specifically, the thickness of the portion approaching the main magnetic pole 11 is thinner than the other portions.

  As already described, the relatively low saturation magnetic flux density soft magnetic layer 14 applied to the shield member does not constitute the shield end. The same part determines the amount of magnetic flux passing through the shield, and as a result, achieves both a strong magnetic field and a high magnetic field gradient. The soft magnetic layer 12 having a relatively high saturation magnetic flux density stacked on the soft magnetic layer 14 having a relatively low saturation magnetic flux density has a function of flowing a relatively large amount of magnetic flux because the film thickness is thick. As a result, a magnetic charge is generated on the connection surface between the soft magnetic layer 14 having a relatively low saturation magnetic flux density and the soft magnetic layer 12 having a relatively high saturation magnetic flux density due to a difference in passing magnetic flux. If the magnetic charge generation site is far from the shield end, there is little interaction with the main magnetic pole 11, and the leakage magnetic field strength is not changed. This effect acts in the direction of improving the magnetic field distribution in the track width direction.

  In this modification, the thickness of the soft magnetic layer 14 having a relatively low saturation magnetic flux density in the portion approaching the main magnetic pole 11 is reduced. As a result, the connection surface with the soft magnetic layer 12 having a relatively high saturation magnetic flux density approaches the main magnetic pole 11. As a result, the interaction between the magnetic charge generated in the region and the main magnetic pole 11 becomes remarkable. That is, the flow of magnetic flux from the main magnetic pole 11 to the shield part immediately above it is promoted. As a result, it was confirmed that the magnetic field gradient at the same site was improved.

  This effect limits the flow of magnetic flux in the undesired track width direction by increasing the thickness of the soft magnetic layer 14 having a relatively low saturation magnetic flux density. In particular, the flow of magnetic flux is promoted by reducing the thickness of the soft magnetic layer 14 having a low saturation magnetic flux density (as a result, bringing the soft magnetic layer 12 having a relatively high saturation magnetic flux density closer). In short, the distribution of the magnetic flux to be flowed is controlled by the film thickness of the soft magnetic layer 14 having a relatively low saturation magnetic flux density.

  In order to realize this modification, after laminating a soft magnetic layer 14 having a relatively low saturation magnetic flux density, a resist pattern having an opening is disposed in the vicinity of the main magnetic pole, and the resist pattern is relatively positioned with respect to the mask. After the soft magnetic layer 14 having a low saturation magnetic flux density is etched by an ion milling method or the like, the resist pattern is selectively removed, and then the soft magnetic layer 12 having a relatively high saturation magnetic flux density is stacked to easily form the soft magnetic layer 14. it can.

  In the above-described modification, the soft magnetic layer 14 having a relatively low saturation magnetic flux density is increased or decreased with a gentle slope. This means can be formed by selecting an ion milling incident angle from an oblique direction.

  Also, as shown in FIG. 17, it can be formed by setting the ion milling incident angle in a substantially vertical direction. Even when the soft magnetic layer 14 having a relatively low saturation magnetic flux density having a substantially vertical end face was used, the same effect as described above was obtained. In particular, in the configuration shown in FIG. 17, a configuration in which ion milling of the soft magnetic layer 14 having a relatively low saturation magnetic flux density is completely performed on the main magnetic pole is shown as an extreme example. In this configuration, particularly in the vicinity of the main magnetic pole. There was a special effect in that the magnetic field gradient was sharpened.

<Example 3>
The configuration shown in FIGS. 16 and 17 can also be applied to a configuration in which the magnetic shield is arranged in three directions of the main magnetic pole 11 as shown in FIG. Also in this case, after forming the soft magnetic layer 13 having a relatively high saturation magnetic flux density, a soft magnetic layer 14 having a relatively low saturation magnetic flux density is laminated on the upper side and both sides of the soft magnetic layer 14, and then the main pole 11 can be formed by providing a resist pattern having an opening in a portion facing the trailing side, and etching the soft magnetic layer 14 having a relatively low saturation magnetic flux density by the ion milling method or the like using the resist pattern as a mask. (The subsequent steps are the same as above.)

  Even in this configuration, the flow of magnetic flux near the trailing side of the main magnetic pole is promoted, so that a high magnetic field gradient is obtained. In particular, this configuration can realize a configuration in which the soft magnetic layer 12 having a relatively high saturation magnetic flux density is not disposed on both sides of the main magnetic pole 11. As an effect, a magnetic field distribution in which the spread of the magnetic field in the track width direction is suppressed can be obtained, and a magnetic disk device with a high track density can be realized.

2 is an enlarged view of a main part of a recording head of a perpendicular magnetic recording head according to Embodiment 1. FIG. 1 is a conceptual diagram of a magnetic disk device using a perpendicular magnetic recording head according to the present invention. 2 is a cross-sectional view of a perpendicular magnetic recording head according to Embodiment 1. FIG. FIG. 6 is a diagram showing the calculation results of the magnetic field strength and magnetic field gradient of the perpendicular magnetic recording head according to Example 1. It is a figure which shows the calculation result of the magnetic field intensity and magnetic field gradient of a conventional head. FIG. 6 is a diagram showing the calculation results of the magnetic field strength and magnetic field gradient of the perpendicular magnetic recording head according to Example 1. FIG. 6 is a diagram showing the calculation results of the magnetic field strength and magnetic field gradient of the perpendicular magnetic recording head according to Example 1. FIG. 6 is a diagram illustrating a calculation result of a magnetic field strength distribution in the track width direction of the perpendicular magnetic recording head according to the first embodiment. It is the figure which expanded a part of FIG. 6 is a diagram illustrating a calculation result of a magnetic field strength gradient in the recording direction of the perpendicular magnetic recording head according to Example 1. FIG. 6 is an enlarged view of a main part of a recording head of a perpendicular magnetic recording head according to Embodiment 2. FIG. 6 is a diagram illustrating calculation results of a saturation magnetic flux density and a magnetic field gradient of a second soft magnetic layer of a perpendicular magnetic recording head according to Example 2. FIG. 6 is a diagram showing a configuration of a magnetic shield according to a modification of Example 2. FIG. It is a figure which shows the structure of the magnetic shield by the other modification of Example 2. FIG. It is a figure which shows the structure of the magnetic shield by the other modification of Example 2. FIG. It is a figure which shows the structure of the magnetic shield by the other modification of Example 2. FIG. It is a figure which shows the structure of the magnetic shield by the other modification of Example 2. FIG. 6 is an enlarged view of a main part of a recording head of a perpendicular magnetic recording head according to Embodiment 3. It is a figure which shows the calculation result of the magnetic field intensity and magnetic field gradient of a conventional head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Perpendicular magnetic recording head, 2 ... Recording medium, 3 ... Motor, 4 ... Rotary actuator, 5 ... Circuit board, 6 ... Recording / reproducing circuit, 7 ... Arm, 8 ... Suspension, 10 ... Recording head, 11 ... Main pole , 12 ... third soft magnetic layer, 13 ... first soft magnetic layer, 14 ... second soft magnetic layer, 15, 15 '... magnetic shield, 16 ... first magnetic layer, 17 ... second magnetic layer, 18, 18 -1, 18-2 ... Coil, 19-1, 19-2, 19-3, 19-4 ... Non-magnetic film, 30 ... Read head, 31 ... Slider substrate, 32 ... Underlayer, 33 ... Lower shield, 34 ... reproducing element, 35 ... upper shield, 42 ... third magnetic layer, 98 ... air bearing surface.

Claims (20)

The main pole,
A first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main pole;
A second magnetic layer magnetically connected to the first magnetic layer on the side opposite to the air bearing surface;
A coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer;
A magnetic shield provided on the trailing side and both sides of the main magnetic pole via a nonmagnetic layer,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities. A first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main magnetic pole side, and a periphery of the first soft magnetic layer. A second soft magnetic layer having a relatively low saturation magnetic flux density formed; and a third soft magnetic layer having a relatively high saturation magnetic flux density formed around the second soft magnetic layer. A perpendicular magnetic recording head.   2. The perpendicular magnetic recording head according to claim 1, wherein the thickness of the second soft magnetic layer is larger than the minimum length of the magnetic shield in the depth direction.   2. The perpendicular magnetic recording head according to claim 1, wherein the thickness of the second soft magnetic layer is larger than the thickness of the first soft magnetic layer.   4. The perpendicular magnetic recording head according to claim 3, wherein the thickness of the third soft magnetic layer is larger than the thickness of the second soft magnetic layer.   2. The perpendicular magnetic recording head according to claim 1, wherein the first and third soft magnetic layers are made of a NiFeCo alloy, and the second soft magnetic layer is made of a NiFe alloy.   2. The perpendicular magnetic recording head according to claim 1, wherein a length of the third soft magnetic layer in a depth direction becomes longer as the distance from the main magnetic pole is increased.   2. The perpendicular magnetic recording head according to claim 1, wherein lengths of the second and third soft magnetic layers in the depth direction become longer as the distance from the main magnetic pole increases.   2. The perpendicular magnetic recording head according to claim 1, wherein notches are provided on the air bearing surface side and trailing side of the main pole, and the first and second soft magnetic layers are formed in the notch portions, and A perpendicular magnetic recording head, wherein a rear end portion of the second soft magnetic layer is formed on the nonmagnetic layer.   2. The perpendicular magnetic recording head according to claim 1, wherein the thickness of the second soft magnetic layer in a portion adjacent to the trailing side of the main magnetic pole is smaller than that in the other portions.   2. The perpendicular magnetic recording head according to claim 1, further comprising a reproducing head. The main pole,
A first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main pole;
A second magnetic layer magnetically connected to the first magnetic layer on the side opposite to the air bearing surface;
A coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer;
A magnetic shield provided on the trailing side of the main pole via a nonmagnetic layer,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities, and includes a first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main pole, and an upper surface of the first soft magnetic layer. A second soft magnetic layer having a relatively low saturation magnetic flux density formed on the second soft magnetic layer, and a third soft magnetic layer having a relatively high saturation magnetic flux density formed on the second soft magnetic layer. A perpendicular magnetic recording head.   12. The perpendicular magnetic recording head according to claim 11, wherein the thickness of the second soft magnetic layer is larger than the minimum length of the magnetic shield in the depth direction.   12. The perpendicular magnetic recording head according to claim 11, wherein the thickness of the second soft magnetic layer is larger than the thickness of the first soft magnetic layer.   12. The perpendicular magnetic recording head according to claim 11, wherein the length of the third soft magnetic layer in the depth direction increases as the distance from the main magnetic pole increases.   12. The perpendicular magnetic recording head according to claim 11, wherein lengths of the second and third soft magnetic layers in a depth direction become longer as the distance from the main magnetic pole increases.   12. The perpendicular magnetic recording head according to claim 11, wherein a notch is provided on the air bearing surface side and the trailing side of the main magnetic pole, the first and second soft magnetic layers are formed in the notch portion, and A perpendicular magnetic recording head, wherein a rear end portion of the second soft magnetic layer is formed on the nonmagnetic layer.   12. The perpendicular magnetic recording head according to claim 11, wherein a thickness of the second soft magnetic layer in a portion adjacent to the main magnetic pole is smaller than that in other portions.   12. The perpendicular magnetic recording head according to claim 11, wherein the second soft magnetic layer is formed in a portion excluding a portion facing the main magnetic pole.   12. The perpendicular magnetic recording head according to claim 11, further comprising a reproducing head. The main pole,
A first magnetic layer magnetically connected to the opposite side of the air bearing surface of the main pole;
A second magnetic layer magnetically connected to the first magnetic layer on the side opposite to the air bearing surface;
A coil that circulates a magnetic circuit composed of the main magnetic pole, the first magnetic layer, and the second magnetic layer;
A magnetic shield provided on the trailing side and both sides of the main magnetic pole via a nonmagnetic layer,
The magnetic shield has a laminated structure of soft magnetic layers having different saturation magnetic flux densities. A first soft magnetic layer having a relatively high saturation magnetic flux density formed on the main magnetic pole side, and a periphery of the first soft magnetic layer. A formed soft magnetic layer having a relatively low saturation magnetic flux density and having a thickness in a portion close to the main pole smaller than that of the other portion, and an upper portion of the second soft magnetic layer; A perpendicular magnetic recording head comprising: a third soft magnetic layer having a relatively high saturation magnetic flux density.

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