JP2009099167A - Recording current determination method and magnetic disk drive device - Google Patents

Abstract

In a magnetic disk drive device for perpendicular magnetic recording, the problem of data erasure due to flux from a main pole toward a leading shield is prevented.
In an HDD manufacturing process according to an embodiment of the present invention, a magnetic head is screened for RFPE to identify a magnetic head that causes RFPE. Further, in the HDD manufacturing method of the present embodiment, the recording current value for writing user data is set in accordance with different rules for the magnetic head (RFPE head) that causes RFPE and the normal magnetic head. By setting an appropriate current value as the recording current of the RFPE head, generation of RFPE in the RFPE head can be prevented and the RFPE head can be mounted on the HDD.
[Selection] Figure 1

Description

  The present invention relates to a recording current determination method and a magnetic disk drive apparatus, and more particularly to determination of a recording current of a recording head for perpendicular magnetic recording having a trailing shield.

  The magnetic recording / reproducing apparatus includes a magnetic recording medium and a magnetic head, and data on the magnetic recording medium is read and written by the magnetic head. In order to increase the recording capacity per unit area of the magnetic recording medium, it is necessary to increase the surface recording density. However, when the bit length to be recorded becomes small, there is a problem that the surface recording density cannot be increased due to thermal fluctuation of the magnetization of the medium. In general, the influence of thermal fluctuation becomes larger as the value of Ku · V / kT (Ku is the magnetic anisotropy constant, V is the minimum magnetization unit volume, k is the Boltzmann constant, and T is the absolute temperature) is smaller. Therefore, in order to reduce the influence of thermal fluctuation, it is necessary to increase Ku or V.

  As a solution to this problem, there is a perpendicular recording method in which a magnetization signal is recorded in a direction perpendicular to a two-layer perpendicular medium having a soft magnetic backing layer with a single pole head. When this method is used, a stronger recording magnetic field can be applied to the medium. Therefore, a recording layer having a large magnetic anisotropy constant (Ku) can be used. Further, the perpendicular magnetic recording type magnetic recording medium has an advantage that V can be increased by growing the magnetic particles in the film thickness direction while keeping the particle diameter of the medium surface small, that is, the bit length is small.

  Several recording head structures for such perpendicular recording magnetic heads are known. FIG. 9 shows the relationship between the perpendicular recording magnetic head 14 and the magnetic disk 11 and an outline of perpendicular recording. The magnetic disk 11 has a magnetic recording layer 19 and a soft magnetic backing layer 20, which is a layer below the magnetic recording layer 19, on a flat nonmagnetic substrate 22. In the conventional magnetic head, the lower shield 8, the reproducing element 7, the upper shield 9, the auxiliary magnetic pole 3, the thin film coil 2, and the main magnetic pole 1 are laminated in this order from the head running direction side (leading side). The lower shield 8, the reproducing element 7, and the upper shield 9 constitute a reproducing head 24, and the auxiliary magnetic pole 3, the thin film coil 2, and the main magnetic pole 1 constitute a recording head (single magnetic pole head) 25.

  The main magnetic pole 1 includes a main magnetic pole yoke portion 1A joined to the auxiliary magnetic pole via a pillar 17 and a main magnetic pole pole tip 1B which is exposed on the air bearing surface and defines the track width. The magnetic field emitted from the main magnetic pole 1 of the recording head 25 passes through the magnetic recording layer 19 and the soft magnetic backing layer 20 of the magnetic disk medium 11 to form a magnetic circuit that enters the auxiliary magnetic pole 3, and records a magnetization pattern on the magnetic recording layer 19. To do. An intermediate layer may be formed between the magnetic recording layer 19 and the soft magnetic backing layer 20. As the reproducing element 7 of the reproducing head 24, a giant magnetoresistive element (GMR), a tunnel magnetoresistive element (TMR), or the like is used.

  Along with the magnetic field strength of the recording head, the magnetic field gradient in the head magnetic field vertical component profile that records the boundary of the recording bit cell, that is, the magnetic field gradient of the head magnetic field vertical component profile in the head running direction is also an important factor for realizing high recording density It is. In the future, in order to achieve a higher recording density, the magnetic field gradient must be further increased. In order to improve the recording magnetic field gradient, as shown in FIG. 9, there is a structure in which a magnetic material, so-called trailing shield 32 is disposed on the trailing side of the main pole 1 (see, for example, Patent Document 1).

The head structure shown in FIG. 9 has a drawback that the recording / reproducing interval is increased and the format efficiency is deteriorated because the auxiliary magnetic pole 3 and the thin film coil 2 exist between the reproducing element 7 and the main magnetic pole 1. Therefore, as shown in FIG. 10, a structure in which the auxiliary magnetic pole 3 is arranged on the trailing side of the main magnetic pole 1 is also applied. With this structure, the recording / reproducing interval can be reduced. As shown in FIG. 10, it is proposed to arrange the trailing shield 32 even when the auxiliary magnetic pole 3 forming the closed magnetic path is arranged on the trailing side of the main magnetic pole 1.
JP 2007-257711 A

  Since the trailing shield 32 absorbs the flux from the main magnetic pole 1, the gradient of the write magnetic field is improved, which may lead to an improvement in SN. However, the trailing shield 32 may cause return filed-induced partial erasure (RFPE). RFPE is a phenomenon in which the flux from the main pole 1 to the trailing shield 32 partially erases data on the recording surface. Specifically, as shown in FIG. 11, a path is formed in which the flux from the main pole 1 returns to the trailing shield 32 through the soft magnetic backing layer 20. This return flux may cause a problem that data already written in the magnetic recording layer 19 is partially erased. Therefore, a technique for solving this RFPE problem is required in the magnetic recording / reproducing apparatus.

  One aspect of the present invention is a method for determining a recording current value in writing user data for a perpendicular magnetic recording head having a trailing shield. In this method, data is written to the magnetic disk by the recording head while changing the magnetic field strength to the magnetic disk. The written data is read, and saturation characteristics are measured for a predetermined parameter of the recording head. Based on the measurement result of the saturation characteristic, it is determined whether data erasure has occurred due to a flux path from the main pole of the recording head to the trailing shield. When the data erasure has not occurred, a recording current value in writing the user data is determined according to a first rule. When the data erasure has occurred, a recording current value for writing the user data is determined according to a second rule different from the first rule. For the normal head and the head that causes data erasure, the recording current value is determined according to different rules to improve the manufacturing yield of the magnetic disk drive device, or by the flux from the main pole to the leading shield Data erasure can be prevented.

  By changing the clearance between the perpendicular magnetic recording head and the magnetic disk, the magnetic field strength to the magnetic disk can be changed. Preferably, the magnetic field strength to the magnetic disk is changed by changing the recording current value of the perpendicular magnetic recording head, and the saturation characteristic of the error rate as the parameter is measured. As a result, accurate determination can be made by efficient measurement.

  Preferably, it is determined that data erasure has occurred when the parameter is improved after being improved in accordance with the increase in the magnetic field strength, and the degree of deterioration after the improvement exceeds the first reference. As a result, it is possible to accurately determine whether data is erased. Furthermore, it is preferable that the recording head is determined to be a fail head when the degree of deterioration exceeds a second reference that is greater than the first reference. Thereby, occurrence of data erasure can be prevented more reliably.

  Preferably, by changing a recording current value of the perpendicular magnetic recording head, a magnetic field strength to the magnetic disk is changed, and a parameter value in a predetermined recording current value after deterioration and a predetermined value before deterioration are determined. The presence or absence of the data erasure is determined based on the ratio of the recorded current value to the parameter value. As a result, accurate determination can be made by efficient measurement.

  By changing the recording current value of the perpendicular magnetic recording head, the magnetic field strength to the magnetic disk is changed, and according to the second rule, the current value equal to or lower than the current value at which the parameter shows the best value is set to the user It is preferable to determine the recording current value in data writing. As a result, the required writing intensity can be realized and the influence on the adjacent track can be reduced.

  Another embodiment of the present invention is a magnetic disk drive device. This magnetic disk drive device includes a magnetic disk, a perpendicular magnetic recording head having a trailing shield and a main magnetic pole for writing data while changing the magnetic field strength to the magnetic disk, and reproducing for reading the written data. A head and a controller; This controller uses the data read by the reproducing head to measure the saturation characteristics of the predetermined parameters of the perpendicular magnetic recording head, and based on the measurement results, data based on the flux from the main pole to the trailing shield It is determined whether erasure has occurred, a recording current value for writing user data is determined according to a first rule when the data erasure has not occurred, and when the data erasure has occurred, the first A recording current value in writing the user data is determined according to a second rule different from the first rule. For the normal head and the head that causes data erasure, the recording current value is determined according to different rules to improve the manufacturing yield of the magnetic disk drive device, or by the flux from the main pole to the leading shield Data erasure can be prevented.

  According to the present invention, in a magnetic disk drive device for perpendicular magnetic recording, it is possible to prevent the problem of data erasure due to flux from the main pole toward the leading shield.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same element, and duplication description is abbreviate | omitted as needed for clarification of description. In the embodiment described below, the present invention is applied to a hard disk drive (HDD) which is an example of a magnetic disk drive device.

  The magnetic head of this embodiment is a perpendicular magnetic recording magnetic head, and has the same structure as the head structure described with reference to FIGS. The magnetic head has a reproducing head and a recording head. The recording head of this embodiment is a perpendicular magnetic recording head and has a main magnetic pole that is a single magnetic pole and a trailing shield. The trailing shield can increase the magnetic field gradient of the head magnetic field vertical component profile in the head traveling direction. On the other hand, as described with reference to FIG. 11, the recording head for perpendicular magnetic recording having a trailing shield causes RFPE (Return Filed-induced Partial Erasure) due to the flux returning from the main pole to the trailing shield. Yes.

  In the manufacturing process of the HDD of this embodiment, magnetic heads are screened for RFPE, and the magnetic head that causes RFPE is specified. Further, in the HDD manufacturing method of the present embodiment, the recording current value for writing user data is set in accordance with different rules for the magnetic head (RFPE head) that causes RFPE and the normal magnetic head. By setting an appropriate current value as the recording current of the RFPE head, generation of RFPE in the RFPE head can be prevented and the RFPE head can be mounted on the HDD.

  The overall flow of the RFPE screening method and recording current setting method of this embodiment will be described with reference to the flowchart of FIG. The identification of the RFPE head and the setting of the recording current value by screening are used in the manufacturing process of the head gimbal assembly (HGA) or the manufacturing process of the HDD, and the HDD may perform it as an internal operation. . In the following, an example in which the test apparatus connected to the HDD performs the screening and setting of the recording current value will be described.

  As shown in FIG. 1, the test apparatus writes data on a magnetic disk with different write strengths by means of a magnetic head in the HDD. (S11). The write intensity is determined by the recording magnetic field intensity entering the magnetic disk. If the recording magnetic field intensity entering the magnetic disk is strong, the writing intensity is also strong. There are two methods for changing the magnetic field strength to the magnetic disk, one is a method for changing the recording current value, and the other is a method for changing the clearance between the recording head and the magnetic disk.

  As a mechanism for changing the clearance, there are a microactuator using a piezo element and a mechanism for adjusting the clearance by expanding and projecting the recording head by an internal heater of the magnetic head. For RFPE head screening, both clearance adjustment and recording current adjustment are suitable. However, for setting the recording current, the characteristics of the magnetic head (recording head) can be changed by changing the recording current. It is efficient to measure.

  The test apparatus reads data written by the magnetic head with different writing intensities using the magnetic head, and measures a predetermined parameter of the magnetic head (S12). Parameters that can be used to identify the RFPE head include error rate, read signal strength, read signal SN, resolution, etc. Among them, the error rate is particularly suitable. A specific example using the error rate will be described later.

  The test apparatus specifies the saturation characteristic of the measured parameter (S13). Further, it is determined from the specified saturation characteristic whether or not RFPE is generated in the magnetic head (S14). The determination method will be described later. When RFPE has not occurred and the magnetic head being measured is normal (N in S14), the test apparatus writes the user data of the magnetic head according to a predetermined rule for the normal magnetic head. The recording current value is determined and the value is set in the HDD (S15).

  When it is determined that RFPE is occurring (Y in S14), the test apparatus determines the degree of the RFPE (S16). When strong RFPE exceeding the reference is occurring (S in S16), the test apparatus determines that the magnetic head is in failure (S17). The magnetic head determined to be failed is not used, and the HDD is reworked. When the RFPE within the reference is occurring (W in S16), the test apparatus determines a recording current value for writing the user data of the magnetic head according to a predetermined rule for the RFPE head, and calculates the value. The HDD is set (S18).

  The rules for determining the recording current are different between the normal head and the RFPE head that causes the RFPE. In this way, by determining the recording current by applying an appropriate rule to each of the RFPE head and the normal head, the writing characteristics of each recording head can be made appropriate. Furthermore, even if a magnetic head having a recording head that causes RFPE can be mounted on an HDD, the yield of HGA and HDD manufacturing can be improved.

  As described above, in RFPE screening, it is preferable to change the magnetic field strength to the magnetic disk by changing the recording current. The parameter used for RFPE determination is preferably an error rate. A method for measuring the saturation characteristic of the error rate will be described with reference to the flowchart of FIG. This flowchart corresponds to the processing of steps S11 to S13 in FIG.

  The test apparatus writes data on the magnetic disk using the recording head of the magnetic head (S111). Next, the test apparatus reads the data written using the reproducing head of the same magnetic head (S112), and measures the error rate (S113). The test apparatus measures the error rate at a plurality of different recording currents. If an unmeasured recording current value remains (N in S114), the test apparatus increases the recording current value (S115) and repeats steps S111 to S113. When the error rate measurement is completed for all preset recording current values (Y in S114), the error rate measurement process is completed. Note that after writing all the data at different recording currents, they may be read out. Further, the order of writing different recording current values is not particularly limited.

FIG. 3A schematically shows typical examples of an error rate saturation characteristic of a magnetic head causing RFPE and an error rate saturation characteristic of a normal magnetic head. In FIG. 3A, the X axis is a recording current value, and the Y axis is an error rate. The error rate is expressed as a power of 10, and the Y-axis indicates the power value. For example, if the error rate is 10 ⁻⁵ , the Y-axis value is −5. The minimum error rate is zero.

  As shown in FIG. 3A, in a normal magnetic head, the error rate improves (becomes smaller) as the recording current increases and saturates to a substantially constant value. In contrast, the RFPE head exhibits abnormal saturation characteristics. Specifically, in a magnetic head that causes RFPE, the error rate improves as the recording current increases, and after the best error rate is exhibited at a specific recording current, it worsens (increases) again. Such a change in the error rate in the RFPE head is considered to be caused by an increase in the strength of the RFPE while the writing strength by the main pole is increased by the increase in the recording current.

  Such a change is the same in parameters other than the error rate. As the signal strength deteriorates, the signal strength value decreases. When the SN deteriorates, the intensity of the noise component becomes relatively strong, and the signal intensity becomes relatively small with respect to the noise. These parameters also improve mainly with an increase in recording current, and worsen with an increase in recording current from a specific recording current value.

  As shown in FIG. 3B, when the recording current increases, the flux from the main magnetic pole to the auxiliary magnetic pole for data recording increases and the error rate decreases, while the main magnetic pole moves to the trailing shield. As a result, the RFPE clearly appears from a specific recording current. This RFPE degrades the error rate with increasing recording current. The actual error rate is thought to change from decreasing to increasing with increasing recording current due to these two fluxes.

  Thus, there is a difference in error rate saturation characteristics between the normal head and the RFPE head. Therefore, the test apparatus can specify the presence or absence of RFPE from the error rate saturation characteristics of the magnetic head. In the following, referring to the flowchart of FIG. 4, a process for determining RFPE from the saturation characteristic of the error rate with respect to the recording current will be described. This corresponds to steps S13 to S18 in the flowchart of FIG.

  The test apparatus specifies the saturation characteristics of the error rate with respect to the recording current from the measurement values of the error rate at a plurality of different recording currents (S131). Furthermore, the test apparatus determines whether the saturation characteristic indicates abnormality. In determining saturation characteristic abnormality, the test apparatus performs different processing depending on the degree of abnormality. The determination of the degree of abnormality can be based on the degree of deterioration of the error rate after improvement. When the degree of saturation characteristic abnormality (the degree of deterioration of the error rate) is within the first reference (N in S132), the test apparatus does not cause RFPE and the normal magnetic head It is determined that Therefore, for the magnetic head, the recording current value in writing user data is determined according to the rules of the normal head, and the value is set in the HDD (S133).

  When the degree of saturation characteristic abnormality exceeds the first reference, the test apparatus determines that RFPE is occurring in the magnetic head. Further, when the degree of abnormality of the saturation characteristic exceeds the second reference larger than the first reference (Y in S134), the test apparatus determines that the magnetic head is a fail head (S135). This is because use of a magnetic head having an extremely strong RFPE in the HDD impairs reliability. If the degree of abnormality of the saturation characteristic exceeds the first reference but is within the second reference (N in S134), the test apparatus determines the recording current value for writing user data according to the rules of the RFPE head, The value is set in the HDD (S136).

  FIG. 5A is a diagram for explaining a method for determining the degree of abnormality of the error rate saturation characteristic. In the graph of FIG. 5A, the X axis indicates the value of the best error rate that is the minimum value in the error rate measurement. The Y axis indicates the error rate at the maximum current value in the error rate measurement. As understood from the measurement result of the error rate in FIG. 5B, the value of the best error rate of the normal head substantially matches the error rate at the maximum recording current value. Therefore, in the graph of FIG. 5A, the line of the normal head passes through the origin and becomes a linear function with a slope of 1.

  On the other hand, in the RFPE head, the error rate at the maximum recording current value is larger than the minimum error rate. This is because, as shown in FIG. 5B, the error rate of the RFPE head shows a minimum value and then deteriorates (increases) as the recording current increases. The test apparatus determines that the magnetic head whose error rate falls within the region defined by the large triangle in FIG. 5A is an RFPE head. In an actual magnetic head, it is assumed that there is no magnetic head in which the maximum recording current value shows a value above a large triangle. It is also assumed that there is no magnetic head whose best error rate is smaller or larger than a large triangle. Since the magnetic head has undergone an inspection process before performing the RFPE screening, the above condition is satisfied.

  In FIG. 5A, a gap exists between a triangle indicating the RFPE head and a function line indicating the normal head. This corresponds to a margin. In some normal heads, the error rate at the maximum recording current is greater than the minimum error rate. However, if the difference is small, it is within the range of the manufacturing range, so the test apparatus determines that such a magnetic head is a normal magnetic head. The triangle indicating RFPE is composed of two linear function lines with different slopes and a line with a constant X that connects these lines with a specific best error rate value. A linear function line with a small slope is above a linear function line with a large slope. A large error rate at the maximum recording current means that the degree of abnormality of the saturation characteristic is large accordingly. Therefore, when there is an error rate in the triangular area hatched with diagonal lines in FIG. 5A, the test apparatus of this embodiment determines that the magnetic head is a fail head.

  The triangle indicating the fail is an upper part of the triangle indicating the RFPE, and the slope of the linear function line below the triangle indicating the fail is between the slopes of the two linear function lines of the triangle indicating the RFPE. An error rate (magnetic head) in which the ratio of the error rate at the maximum recording current value to the best error rate exceeds the reference is included in the triangle indicating the failure. The test apparatus determines a recording current value Iw in writing user data for a magnetic head included in a region excluding the triangle indicating RFPE from the triangle indicating RFPE. At this time, the decision rule followed by the test apparatus is a decision rule for an RFPE head different from a normal magnetic head.

  In a preferred example, the test apparatus determines that the magnetic head is an RFPE head when the error rate at the maximum recording current value is greater than a value represented by a predetermined quadratic function of the best error rate. Further, when the error rate at the maximum recording current value is larger than a value represented by a predetermined linear function of the best error rate, the test apparatus determines that the magnetic head is a fail head. By using a quadratic equation for the best error rate for RFPE determination, a more accurate determination can be made in a magnetic head that tends to vary in measurement as the best error rate becomes better.

As described above, it is preferable to use the best error rate and the error rate at the maximum current value to determine the degree of abnormality of the error rate saturation characteristic. It is also possible to use a predetermined recording current value and its error rate value.

  A preferred example of the method for determining the recording current will be described with reference to FIG. The recording current is preferably as small as possible as long as the error rate is within a predetermined standard. The reliability of the error rate can be ensured if the design value is satisfied. When the recording current is large, the influence on the adjacent data track becomes large. From this viewpoint, the recording current is preferably small.

  In a preferred example, the test apparatus normally fits the measured values of the recording current and error rate with a quartic function in order to determine the recording current of the head. Further, the second derivative of the quartic function is calculated, and the maximum value (vertex) is calculated. The test apparatus specifies a recording current value at which the quadratic function has a maximum value of the second derivative, and adds a predetermined offset value to the recording current value Iwn. When the recording current value at the peak of the second derivative is used, the magnetic head is used in an area where the sensitivity is high with respect to the recording current. For this reason, it may not be possible to have a sufficient margin for variations in the magnetic recording layer of the magnetic disk. Therefore, by adding a predetermined offset value to the recording current value at the peak of the second derivative, a sufficient margin for variations in the magnetic recording layer of the magnetic disk is ensured.

  For a magnetic head that causes FRPE, the test apparatus determines a recording current by applying a rule different from that of a normal head. As in the case of the normal magnetic head, the test apparatus fits the measured values of the recording current and the error rate with a quartic function. Further, the second derivative of the quartic function is calculated, and the point indicating the maximum value is specified. The test apparatus determines the recording current value at the peak of this second derivative as the recording current value Iwr of the FRPE head. The recording current value Iwr of the FRPE head is slightly smaller than the recording current value with the smallest (best) error rate in FIG.

  Since the FRPE head exhibits an error rate characteristic different from that of the normal head, an appropriate recording current cannot be determined by the same method. Since the FRPE head error rate shows a decrease and an increase as the recording current increases, an appropriate recording current value can be determined by using the analysis method as described above. That is, it is possible to set a recording current value that can realize a necessary error rate and sufficiently reduce the influence on adjacent data tracks.

  The recording current determination method is based on the condition that the temperature is constant. However, as shown in FIG. 7A, RFPE depends on temperature. As the temperature increases, the recording layer of the magnetic disk changes due to a smaller magnetic field. Therefore, the graph showing the relationship between the recording current of the magnetic head showing RFPE and the error rate shows a change that shifts to the low recording current side as the temperature rises.

  In setting the recording current of the magnetic head, it is preferable to consider the temperature dependence of RFPE. In a preferred example, the test apparatus performs error rate measurements at different temperatures. By specifying a recording current value that causes RFPE at different environmental temperatures, a recording current value that does not cause RFPE can be set within the guaranteed design temperature range of the HDD, as shown in FIG. 7B. In FIG. 7B, the dotted line is the recording current that causes RFPE, and the white circle is the measured value.

  Specifically, the test apparatus determines the recording current value at a plurality of different temperatures. This determination method is the same as the recording current determination method. For example, the test apparatus specifies a linear function connecting the set recording current values at each temperature, and sets the linear function in the HDD. The HDD identifies the recording current value according to the set function. When it is difficult to measure the error rate at a plurality of temperatures in manufacturing the HDD, the test apparatus measures the error rate only at one temperature and determines the recording current value. For recording current values at other temperatures, a function determined in advance by experiment is set in the HDD. This eliminates the need for an additional test apparatus in manufacturing the HDD, and increases the manufacturing efficiency by shortening the test time.

  The RFPE screening and the setting of the recording current are performed in the manufacturing process of the head gimbal assembly or HDD. In the HDD manufacturing process, a head slider is first manufactured, and the head slider is mounted on a suspension. DET (Dynamic Electrical Test) is performed on the manufactured HGA. In this test, an HGA is mounted on a test apparatus, and actual data writing and data reading are performed on a rotating magnetic disk. Preferably, in this DET, the RFPE of this embodiment is screened.

  Next, the head stack assembly (HSA) is manufactured by mounting the HGA that has passed DET on the carriage. The manufactured HSA is mounted in a housing. A spindle motor and a magnetic disk are further mounted in the casing. The assembly having the necessary parts in the housing is called a head disk assembly (HDA). The HDA is mounted with a control circuit board through a servo write process. An HDD composed of an HDA and a control circuit board is an object of an operation test. In addition to the defect detection test, the operation test includes the RFPE screening and recording current setting steps.

  The HDD can specify the RFPE head and set its recording current instead of the test apparatus. In the manufacturing process, the controller of the HDD can perform the above processes, or the HDD as a product can perform these processes when the power is turned on or idling. As shown in the block diagram of FIG. 8, the HDD 100 includes a circuit board 120 fixed to the outside of the enclosure 110. The circuit board 120 includes circuits such as a read / write channel (RW channel) 121, a motor driver unit 122, a hard disk controller (HDC) and an MPU integrated circuit (HDC / MPU) 123, and a RAM 124. In the enclosure 110, a spindle motor (SPM) 114 rotates the magnetic disk 111. Each head slider 112 includes a slider that floats on the magnetic disk 111 and a magnetic head fixed to the slider.

  The arm electronic circuit (AE) 113 selects the head slider 112 that accesses (reads or writes) the magnetic disk 111 from the plurality of head sliders 112 according to the control data from the HDC / MPU 123, and reads the read / write signal. Perform amplification. The head slider 112 is fixed to the tip of the actuator 116. The actuator 16 rotates to move in the radial direction on the magnetic disk 111 that rotates the head slider 12. The assembly of the actuator 116 and the voice coil motor (VCM) is a head moving mechanism. The motor driver unit 122 drives the SPM 114 and the VCM 115 according to control data from the HDC / MPU 123.

  In the read process, the RW channel 121 extracts servo data and user data from the read signal acquired from the AE 113, performs a decoding process, and supplies it to the HDC / MPU 123. In the write process, the write data supplied from the HDC / MPU 123 is code-modulated, converted into a write signal, and supplied to the AE 113. The HDC is a logic circuit, and the MPU operates according to microcode loaded in the RAM 24. The HDC / MPU 123 is an example of a controller, and performs overall control of the HDD 100 in addition to necessary processing relating to data processing such as head positioning control, interface control, and defect management.

  The HDC / MPU 123 controls each element to perform RFPE screening and recording current setting. The HDC / MPU 123 controls the recording current by setting control data in the register of the AE 13. Further, the HDC / MPU 123 has an error correction circuit, and the circuit measures an error rate. The HDD 100 has a temperature detector (not shown) inside, and the HDC / MPU 123 can specify the temperature dependence of the RFPE from the detected temperature.

  As mentioned above, although this invention was demonstrated taking preferable embodiment as an example, this invention is not limited to said embodiment. A person skilled in the art can easily change, add, and convert each element of the above-described embodiment within the scope of the present invention. For example, the present invention can be applied to magnetic disk drive devices other than HDDs.

It is a flowchart which shows the whole flow of the screening method of RFPE, and a recording current setting method. It is a flowchart which shows the method of the measurement of the saturation characteristic of the error rate of this form. It is a figure which shows typically the example of the saturation characteristic of the error rate of the magnetic head which raise | generates RFPE, and the saturation characteristic of the error rate of a normal magnetic head. It is a flowchart which shows the process which determines RFPE from the saturation characteristic of the error rate with respect to the recording current of this form. It is a figure explaining the method to determine the abnormality degree of the error rate saturation characteristic of this form. It is a figure explaining the determination method of the recording current of this form. It is a figure which shows typically the temperature dependence of RFPE. 1 is a block diagram schematically showing an overall configuration of an HDD according to an embodiment. It is a cross-sectional schematic diagram in the track center of a magnetic head and a magnetic recording medium according to a conventional technique. It is a cross-sectional schematic diagram in the track center of a magnetic head and a magnetic recording medium according to a conventional technique. It is a cross-sectional schematic diagram in the track center of a magnetic head and a magnetic recording medium according to a conventional technique. The RFPE by the flux from the main pole to the trailing shield is schematically shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main magnetic pole, 1A Main magnetic pole yoke part, 1B Main magnetic pole Pole tip 2 Thin film conductor coil, 3 Auxiliary magnetic pole, 7 Reproducing element, 8 Lower shield 9 Upper shield, 10 Auxiliary shield, 11 Magnetic disk 14 Magnetic head, 15 Rotary actuator 16 recording head, 17 pillar 19 magnetic recording layer, 20 soft magnetic backing layer, 21 nonmagnetic layer, 22 substrate 23 nonmagnetic layer, 24 reproducing head, 25 recording head, 28 motor 32 magnetic body (trailing shield), 33 Magnetic body (side shield)
DESCRIPTION OF SYMBOLS 100 Hard disk drive, 110 Enclosure, 111 Magnetic disk 112 Head slider, 113 Arm electronic circuit, 116 Actuator 120 Circuit board, 121 Read / write channel 122 Motor driver unit 123 Integrated circuit of hard disk controller and MPU, 124 RAM

Claims (14)

A method for determining a recording current value in writing user data for a perpendicular magnetic recording head having a trailing shield,
Write data to the magnetic disk while changing the magnetic field strength to the magnetic disk by the perpendicular magnetic recording head,
Read the written data, measure saturation characteristics for a predetermined parameter of the perpendicular magnetic recording head,
Based on the measurement result of the saturation characteristics, it is determined whether data erasure has occurred due to a flux path from the main magnetic pole of the perpendicular magnetic recording head to the trailing shield,
If the data erasure has not occurred, determine a recording current value in writing the user data according to the first rule,
When the data erasure occurs, a recording current value in writing the user data is determined according to a second rule different from the first rule.
Method. Changing the magnetic field strength to the magnetic disk by changing the clearance between the perpendicular magnetic recording head and the magnetic disk;
The method of claim 1. By changing the recording current value of the perpendicular magnetic recording head, the magnetic field strength to the magnetic disk is changed,
Measuring the saturation characteristics of the error rate as said parameter,
The method of claim 1. Determining that data erasure has occurred when the parameter deteriorates after being improved according to the increase in the magnetic field strength, and the degree of deterioration after the improvement exceeds the first reference;
The method of claim 1. If the degree of deterioration exceeds a second reference greater than the first reference, the perpendicular magnetic recording head is determined to be a fail head;
The method of claim 4. By changing the recording current value of the perpendicular magnetic recording head, the magnetic field strength to the magnetic disk is changed,
Determining the presence or absence of the data erasure based on a ratio between a parameter value in a predetermined recording current value after deterioration and a parameter value in a predetermined recording current value before deterioration;
The method of claim 4. By changing the recording current value of the perpendicular magnetic recording head, the magnetic field strength to the magnetic disk is changed,
According to the second rule, a current value equal to or lower than a current value at which the parameter shows the best is determined as a recording current value in writing the user data.
The method of claim 1. A magnetic disk;
A perpendicular magnetic recording head having a trailing shield and a main magnetic pole and writing data while changing the magnetic field strength to the magnetic disk; and a reproducing head for reading the written data;
Using the data read by the read head, the saturation characteristic is measured for a predetermined parameter of the perpendicular magnetic recording head, and data erasure due to flux from the main pole to the trailing shield occurs based on the measurement result. If the data erasure has not occurred, a recording current value in writing user data is determined according to the first rule, and if the data erasure has occurred, the first rule A controller for determining a recording current value in writing the user data according to a different second rule;
A magnetic disk drive device. The perpendicular magnetic recording head changes a magnetic field strength to the magnetic disk by changing a clearance between the recording head and the magnetic disk.
The magnetic disk drive apparatus according to claim 8. The perpendicular magnetic recording head changes the magnetic field strength to the magnetic disk by changing the recording current value of the recording head,
The controller measures a saturation characteristic of an error rate as the parameter;
The magnetic disk drive apparatus according to claim 8. The controller determines that data erasure has occurred when the parameter is improved after increasing according to the increase in the magnetic field strength, and the degree of deterioration after the improvement exceeds a first reference.
The magnetic disk drive apparatus according to claim 8. The controller determines that the recording head is a fail head when the degree of deterioration exceeds a second reference greater than the first reference.
The magnetic disk drive apparatus according to claim 11. The perpendicular magnetic recording head changes the magnetic field strength to the magnetic disk by changing the recording current value of the recording head,
The controller determines the presence or absence of the data erasure based on a ratio between a parameter value in a predetermined recording current value after deterioration and a parameter value in a predetermined recording current value before deterioration,
The magnetic disk drive apparatus according to claim 11. The perpendicular magnetic recording head changes the magnetic field strength to the magnetic disk by changing the recording current value of the recording head,
The controller determines, according to the second rule, a current value equal to or lower than a current value at which the parameter is the best as a recording current value in writing the user data.
The magnetic disk drive apparatus according to claim 8.

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