JP2006216202A - Evaluating method of thin film magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an evaluating method of a thin film magnetic head in which a quality of an output property can be evaluated highly accurately by eliminating defective products possibly causing degradation and instability. <P>SOLUTION: In the thin film magnetic head having an antiferromagnetic layer 12, a fixed magnetic layer 13, a non-magnetic conduction layer 14, a spin valve film obtained by laminating free magnetic layers 15, and a hard bias film 20 contacted to both sides of a track width direction of the spin valve film, first, the hard bias film 20 is magnetized in the direction of track width of the hard bias film 20 (first magnetization process), an alternating electric field is applied and the head output property is measured (first measuring process). Next, after the hard bias film 20 is magnetized in the height direction being orthogonal to the track width direction, processing for magnetization in the track width direction is performed at least once, the alternating electric field is applied with the same condition as the first time and the head output property is measured (second measuring process). The quality of the head output property is discriminated by comparing the first time measured result with the second time measured result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for evaluating a thin film magnetic head whose magnetic domain is controlled by a hard bias film.

  In the thin film magnetic head, a characteristic inspection is performed in order to confirm whether or not a standard as a preliminarily specified product is satisfied at the manufacturing stage or before shipment. As this characteristic test, a QST (Quasi Static Test) evaluation test is generally used. The QST evaluation test is a technique for evaluating the reproduction output characteristics and magnetic stability of a thin film magnetic head without using an actual magnetic recording medium. Specifically, an external magnetic field of about 3.98 to 39.8 kA / m is periodically changed in a state where a thin film magnetic head (magnetoresistance effect element) is energized, and the element voltage-external magnetic field characteristics of the thin film magnetic head. A curve (VH curve) is obtained. Then, based on the obtained VH curve, it is within or out of the standard from the viewpoint of reproduction output characteristics, magnetic symmetry / polarity of reproduction output (Asymmetric, Polarity), noise (Barkhausen noise), etc. Determine whether.

  Furthermore, the thin film magnetic head is evaluated by an electro magnetic property (DET) evaluation test using an actual magnetic recording medium at the final stage of the manufacturing process. In the DET evaluation test, a thin film magnetic head is actually levitated on a magnetic recording medium, a recording / reproducing operation is performed, and an output of the thin film magnetic head is evaluated. This DET evaluation test and the QST evaluation test are known to have high correlation. Therefore, if a highly accurate QST evaluation test is performed during the manufacturing process, a non-standard thin film magnetic head can be discovered early.

A thin film magnetic head that passes both the QST evaluation test and the DET evaluation test is shipped as a product.
JP 10-198924 A

  However, even a thin film magnetic head that has passed the QST evaluation test and the DET evaluation test may cause degradation and instability after the test, which deteriorates the yield of the hard disk device on which the thin film magnetic head is mounted. I am letting.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a thin-film magnetic head evaluation method capable of accurately evaluating the quality of output characteristics by excluding defective products that may cause degradation and instability. And

  In the present invention, when a defect is generated in any one of the fixed magnetic layer, the free magnetic layer, and the hard bias film, once the strong magnetic field is applied, the defective portion changes irreversibly. However, the defect part does not return to its original state, and the hard bias film and the spin valve film are strongly magnetized once in the height direction and then re-magnetized in the track width direction to eliminate the defect in the head. It is intended to realize a more accurate output characteristic evaluation by exposing.

  That is, the present invention provides an output characteristic of a thin film magnetic head having hard bias films on both sides in the track width direction of a spin valve film formed by laminating an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. A first magnetization step of magnetizing the hard bias film in the track width direction, a first measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field, After the bias film is magnetized in the height direction perpendicular to the track width direction, a process of further magnetizing in the track width direction is performed at least once, and the second magnetization is set such that the magnetization direction of the hard bias film is the track width direction. Compared with the magnetic process, the second measurement process in which an alternating electric field is applied under the same conditions as the first measurement to measure the output characteristics of the thin film magnetic head, and the first and second measurement results are compared, and the thin film magnetic Head It is characterized by having a determination step of determining acceptability of the force characteristics.

  The magnetizing magnetic field in the height direction in the second magnetizing step is preferably stronger than the magnetizing magnetic field in the first magnetizing step. According to this aspect, the magnetization of the hard bias film can be easily directed in the height direction. Specifically, the magnitude of the magnetization magnetic field in the track width direction in the first magnetization process and the second magnetization process is about 239 to 398 kA / m, and the magnitude of the magnetization magnetic field in the height direction in the second magnetization process. The thickness is practically about 796 to 1532 kA / m.

  In the determination step, it is practical to use at least one of the output voltage value of the thin film magnetic head and the asymmetry of the output waveform of the thin film magnetic head as the measurement result of the measurement step.

  The measurement process is a dynamic measurement performed with the thin film magnetic head levitated above the magnetic recording medium, even if the thin film magnetic head is stationary with no magnetic recording medium interposed. May be.

  According to another aspect of the present invention, a hard bias film is provided on both sides in the track width direction of a spin valve film formed by laminating an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. A method for evaluating the output characteristics of a thin film magnetic head, in which a first biasing step of magnetizing a hard bias film in the track width direction and a thin film magnetic head stationary without passing through a magnetic recording medium The first static measurement step of measuring the output characteristics of the thin film magnetic head by applying an electric field, and magnetizing the hard bias film in the height direction perpendicular to the track width direction, and further magnetizing in the track width direction Execute the process at least once and measure the output characteristics of the thin-film magnetic head by applying an alternating electric field under the same conditions as in the second magnetization step, in which the magnetization direction of the hard bias film is the track width direction. Second to Excludes the static measurement process of the eyes, the determination process of comparing the first and second static measurement results to determine whether the output characteristics of the thin film magnetic head are good, and the thin film magnetic head determined to be defective in output characteristics And selecting the thin film magnetic head judged to have good output characteristics, and applying the alternating electric field in the state where the extracted thin film magnetic head is floated on the magnetic recording medium, the output characteristics of the thin film magnetic head are A first dynamic measurement step of dynamically measuring, and a process of magnetizing the hard bias film in the height direction perpendicular to the track width direction and then magnetizing in the track width direction at least once, A third magnetization step in which the magnetization direction of the hard bias film is the track width direction, and a second dynamic measurement step in which the output characteristics of the thin film magnetic head are measured by applying an alternating electric field under the same conditions as in the first time. And the first and the first It is characterized by having a round th dynamic measurement results by comparing the final determining final judge the quality of the output characteristics of the thin-film magnetic head step. Thus, if both the characteristic evaluation by the static characteristic measurement and the characteristic evaluation by the dynamic characteristic measurement are performed, the output characteristic of the thin film magnetic head can be evaluated with higher accuracy.

  According to still another aspect of the present invention, a hard bias film is provided on both sides in the track width direction of a spin valve film formed by stacking an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. In this method, the output characteristics of the thin film magnetic head are measured by a first magnetization step of magnetizing the hard bias film in the track width direction and measuring the output characteristics of the thin film magnetic head by applying an alternating electric field. After the second measurement step, the hard bias film is magnetized in the height direction perpendicular to the track width direction and then magnetized in the track width direction at least once, and the magnetization direction of the hard bias film is tracked. A second magnetization step in the width direction, a second measurement step in which an alternating electric field is applied under the same conditions as in the first time to measure the output characteristics of the thin film magnetic head, and the hard bias film is directly aligned with the track width direction. A third magnetization step in which the magnetization direction of the hard bias film is set to the track width direction at least once after the magnetization in the height direction is performed, and the first and The difference between the third measurement step of measuring the output characteristics of the thin film magnetic head by applying an alternating electric field under the same conditions as the second time, and the difference between the first and second measurement results is calculated as the first reference value. Then, the difference between the first and third measurement results is calculated as the second reference value, and the calculated first reference value and the second reference value are compared to determine the output characteristics of the thin film magnetic head. And a determination step for determining pass / fail.

  The magnetizing magnetic field in the height direction in the second magnetizing step and the third magnetizing step is preferably stronger than the magnetizing magnetic field in the first magnetizing step. According to this aspect, the magnetization of the hard bias film can be easily directed in the height direction. Specifically, the magnitude of the magnetizing magnetic field in the track width direction in the first to third magnetizing steps is about 239 to 398 kA / m, and the magnitude of the magnetizing magnetic field in the height direction in the second and third magnetizing steps. The thickness is practically about 796 to 1532 kA / m.

  In the determination step, it is practical to use at least one of the output voltage value of the thin film magnetic head and the asymmetry of the output waveform of the thin film magnetic head as the measurement result of the measurement step.

  The magnetizing magnetic field in the height direction in the second magnetizing step and the magnetizing magnetic field in the height direction in the third magnetizing step may have the same magnetic field strength and the opposite direction of the magnetic field by 180 degrees. preferable. According to this aspect, it is easier to find a defect in the thin film magnetic head than when the direction of the magnetization magnetic field in the height direction is one direction, and the quality of the output characteristics of the thin film magnetic head can be determined with high accuracy.

  According to the present invention, it is possible to obtain a thin film magnetic head evaluation method capable of excluding defective products that may cause degradation and instability and evaluating the quality of output characteristics with high accuracy.

  The present invention will be described below with reference to the drawings. In the figure, the X direction is the track width direction of the thin film magnetic head, the Y direction is the height direction of the thin film magnetic head (spin valve film), and the Z direction is the stacking direction of the layers constituting the thin film magnetic head.

  FIG. 1 is a cross-sectional view showing an embodiment of a thin film magnetic head which is an evaluation object of the method of the present invention. The thin film magnetic head 1 includes a spin valve film 10 that exhibits a giant magnetoresistance effect between a lower magnetic shield layer 2 and an upper magnetic shield layer 3, and hard biases positioned on both sides of the spin valve film 10 in the track width direction. A film 20 and an electrode layer 30 are provided.

  The spin valve film 10 includes a seed layer 11, an antiferromagnetic layer 12, a pinned magnetic layer 13, a nonmagnetic conductive layer 14, a free magnetic layer 15, and a cap layer 16 in order from the lower magnetic shield layer 2 side. The seed layer 11 is made of approximately 20 to 60% of Cr, NiFe alloy, or Ni—Fe—Z alloy (where Z is at least one element selected from Cr, Rh, Ta, Hf, Nb, Zr, and Ti). It is formed with a film thickness of about. This seed layer 11 may not be formed. The antiferromagnetic layer 12 is made of an IrMn alloy or a PtMn alloy, and generates a large exchange coupling magnetic field with the pinned magnetic layer 13 by heat treatment, so that the magnetization direction of the pinned magnetic layer 13 is in the Y direction in the drawing. Fix it.

  The pinned magnetic layer 13 is made of Ru, Rh, Cr, Re, Cu, or the like between the first pinned magnetic layer 13A and the second pinned magnetic layer 13B made of Co, NiFe alloy, CoNi alloy, CoFe alloy, CoFeNi alloy, or the like. The non-magnetic layer 13C is formed in a laminated ferrimagnetic structure. The magnetization of the first pinned magnetic layer 13A is pinned in the Y direction by an exchange coupling magnetic field generated at the interface with the antiferromagnetic layer 12, and is magnetically coupled to the first pinned magnetic layer 13A via the nonmagnetic layer 13C. The coupled second pinned magnetic layer B is pinned in a direction antiparallel to the magnetization direction of the first pinned magnetic layer 13A. In the pinned magnetic layer 13, the magnetic moment per unit area of the first pinned magnetic layer 13A is larger than the magnetic moment per unit area of the second pinned magnetic layer 13B, and the magnetization direction of the first pinned magnetic layer 13A is pinned magnetic. It becomes the magnetization direction as the whole layer. Thus, the magnetization in an artificial ferrimagnetic state is thermally more stable without being fluctuated by an external magnetic field or a high ambient temperature, and there is no possibility that the magnetization direction of the pinned magnetic layer 13 is fluctuated. The pinned magnetic layer 13 may be formed of a magnetic film having a single layer structure or a multilayer structure made of a ferromagnetic material such as Co, NiFe alloy, CoNi alloy, CoFe alloy, CoFeNi alloy. The nonmagnetic conductive layer 14 is formed of a highly conductive material such as Cu, for example, and plays a role of magnetically separating the pinned magnetic layer 13 and the free magnetic layer 15.

  The free magnetic layer 15 has a laminated ferri structure in which a first soft magnetic layer 15A made of a NiFe alloy or a CoNiFe alloy and a second soft magnetic layer 15B are opposed to each other via a nonmagnetic layer 15C made of Ru, Rh, Os, Cr or the like. Is formed. According to the free magnetic layer 15 having the laminated ferrimagnetic structure, the magnetization is easily rotated by the external magnetic field, and the sensor detection accuracy can be further improved. The free magnetic layer 15 has a magnetic moment per unit area of the first soft magnetic layer 15A larger than that of the second soft magnetic layer 15B, and the magnetization direction of the first soft magnetic layer 15A is the same as that of the entire free magnetic layer. It becomes the magnetization direction. The free magnetic layer 15 can also be formed by a single layer film or a laminated film made of a soft magnetic material such as Co, NiFe alloy, CoFe alloy, CoNi alloy, CoNiFe alloy, and specifically, for example, FeNi alloy or CoFeNi alloy. And a Co or CoFe alloy that prevents Ni atoms in the soft magnetic layer from interdiffusing into the nonmagnetic conductive layer 14 interposed between the soft magnetic layer and the nonmagnetic conductive layer 14. You may form with a two-layer structure with a diffusion prevention layer. However, the diffusion prevention layer is formed thin so as not to disturb the magnetic characteristics of the soft magnetic layer. The cap layer 16 is the uppermost layer of the spin valve film 10 and is made of Ta or the like.

  The hard bias film 20 has a CoXPt alloy (where X is Cr, W, Mo, V, Mn, Nb) on the bias underlayer film 21 that covers the end face in the track width direction of the spin valve film 10 and the magnetic shield layer 2. , Ta, or Ti, one or more elements). The hard bias film 20 is magnetized in the track width direction (X direction in the drawing), and the longitudinal bias magnetic field aligns the magnetization of the free magnetic layer 15 in the track width direction. The bias base film 21 is formed of one or more elements of Cr, W, Mo, V, Mn, Nb, and Ta, and has the characteristics (coercivity, squareness ratio) of the hard bias film 20. It has the function of improving and increasing the longitudinal bias magnetic field generated from the hard bias film 20. The electrode layer 30 is made of a highly conductive material such as α-Ta, Au, Rh, Ru, Cr, Cu, or W.

  Next, the thin film magnetic head evaluation method according to the first embodiment of the present invention will be described with reference to FIGS. The evaluation of the output characteristics of the thin film magnetic head is performed at an arbitrary timing from the state in which the thin film magnetic head 1 having the above configuration is cut out from the wafer to before shipment.

  First, as shown in FIG. 2, a static magnetic field H1 of about 398 kA / m from the track width direction is applied to the thin film magnetic head 1 to magnetize the hard bias film 20 of the thin film magnetic head 1 in the track width direction. One magnetization process is performed. The magnetization of the hard bias film 20 is reversible, and the magnetization direction by the last magnetization is maintained. Since the magnetization of the pinned magnetic layer 13 is strongly pinned by the exchange coupling magnetic field generated at the interface with the antiferromagnetic layer 12, the magnetization direction of the pinned magnetic layer 13 does not change even if this magnetization process is performed. On the other hand, since the magnetization of the free magnetic layer 15 is aligned by the longitudinal bias magnetic field of the hard bias film 20, the magnetization direction of the free magnetic layer 15 is also set in the track width direction. The magnitude of the static magnetic field H1 is practically about 239 to 398 kA / m. Hereinafter, the magnetization state of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 shown in FIG. 2 will be described as the first magnetization state of the thin film magnetic head 1.

  Next, the first QST measurement is performed. The QST measurement is a static method for evaluating the reproduction output characteristics and magnetic stability of a thin film magnetic head without using an actual magnetic recording medium. Specifically, the external magnetic field of about 3.98 to 39.8 kA / m is periodically changed while the thin film magnetic head 1 (spin valve film 10) is energized, and the output voltage of the thin film magnetic head 1 is measured. To do. Thereby, an output voltage-external magnetic field characteristic curve (VH curve) of the thin film magnetic head 1 is obtained.

  After the first QST measurement, as shown in FIG. 3, the hard bias film 20 is applied to the thin film magnetic head 1 by applying a strong static magnetic field H2 of 796 kA / m or more from the height direction (Y direction in the drawing) perpendicular to the track width direction. Is strongly magnetized in the height direction, and then a process of re-magnetizing the hard bias film 20 in the track width direction by applying a static magnetic field H1 to the thin film magnetic head 1 from the track width direction as shown in FIG. 2 is executed at least once. To do. By this second magnetization step, the hard bias film 20 is returned to the first magnetization state of FIG. Since the static magnetic field H2 is extremely larger than the static magnetic field H1 when magnetized last time, the magnetization of the hard bias film 20 is easily oriented in the height direction. Accordingly, the magnetization direction of the free magnetic layer 15 is also aligned with the height direction. The magnitude of the static magnetic field H2 is practically about 796 kA / m or more and 1531 kA / m or less.

  In the second magnetization step, the thin film magnetic head 1 returns to the state before the first QST measurement is performed if no defects have occurred in the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20. . However, if any of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has a defect, it can be re-magnetized in the track width direction with a static magnetic field H1 smaller than the static magnetic field H2. The magnetization of the defective portion remains in the height direction and does not return to the initial state. That is, once the hard bias film 20 is strongly magnetized in the height direction and then re-magnetized in the track width direction, the defect portions existing in the fixed magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 are irreversible. And the defective part can be exposed.

  Subsequently, the second QST measurement is performed under the same conditions as the first, and an output voltage-external magnetic field characteristic curve (VH curve) of the thin film magnetic head 1 is obtained.

  Subsequently, the quality of the output characteristics is determined by comparing the first and second QST measurement results. Here, the measurement results to be compared are specifically the output voltage value, the asymmetry of the output voltage waveform (the waveform of the output voltage-external magnetic field characteristic curve), the average value of the peak voltage of the output voltage waveform, and the like.

  Since the first and second QST measurements are performed under the same conditions, the first and second measurement results should be essentially the same. However, if the first and second measurement results differ beyond the measurement error range, the second QST measurement is performed on the thin film magnetic head 1 in a state different from the first QST measurement. In other words, at least one of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has not changed and returned to its original state, and the thin film magnetic head 1 (the pinned magnetic layer 13, the free magnetic layer 15 In addition, it is estimated that defects are generated in the hard bias film 20). Therefore, in this embodiment, when the difference in the QST measurement result exceeds the measurement error range, it is determined that the output characteristic is bad, and when the difference is within the measurement error range, the output characteristic is good.

  FIG. 4 is a graph showing the difference (μV) in the average value of the voltage peak values of the output voltage waveform in the first and second QST measurements, and the horizontal axis x is the output voltage waveform in the first QST measurement. The average value (μV) of the voltage peak value and the vertical axis y indicate the average value (μV) of the voltage peak value of the output voltage waveform in the second QST measurement. FIG. 5 is a graph showing the difference in asymmetry of the output waveform in the first and second QST measurements. The horizontal axis is the asymmetry (%) of the output waveform in the first QST measurement, and the vertical axis is the vertical axis. The asymmetry (%) of the output waveform in the second QST measurement is shown. When the first and second voltage peak average values and the asymmetry match, the marker indicating zero difference in output voltage value is on the straight line satisfying the function y = x when the horizontal axis x and the vertical axis y are Is plotted in A marker markedly deviated from a straight line satisfying the function y = x shown by a dotted line in FIGS. 4 and 5 indicates a defective thin film magnetic head determined to have an output characteristic defect.

  Subsequently, the thin film magnetic head determined to have poor output characteristics is excluded, and the remaining thin film magnetic head, that is, the thin film magnetic head determined to have good output characteristics from the QST measurement result, is subjected to subsequent processing.

  First, the first DET measurement is performed. The DET measurement is a dynamic method for evaluating the reproduction output characteristics and magnetic stability of a thin film magnetic head through an actual magnetic recording medium. Specifically, the recording / reproducing operation is performed for about 1 MHz to 300 MHz in a state where the thin film magnetic head 1 is actually floated on the magnetic recording medium, and the output voltage of the thin film magnetic head 1 is measured.

  After the first DET measurement, as shown in FIG. 3, the hard bias film 20 is applied to the thin film magnetic head 1 by applying a strong static magnetic field H2 of 796 kA / m or more from the height direction (Y direction in the drawing) perpendicular to the track width direction. Is strongly magnetized in the height direction, and then a process of re-magnetizing the hard bias film 20 in the track width direction by applying a static magnetic field H1 to the thin film magnetic head 1 from the track width direction as shown in FIG. 2 is executed at least once. To do. By this third magnetization step, the hard bias film 20 is returned to the first magnetization state of FIG. Since the static magnetic field H2 is extremely larger than the static magnetic field H1 when magnetized last time, the magnetization of the hard bias film 20 is easily oriented in the height direction. Accordingly, the magnetization direction of the free magnetic layer 15 is also aligned with the height direction. The magnitude of the static magnetic field H2 is practically about 796 kA / m or more and 1531 kA / m or less.

  In the third magnetization step, as in the case of the above-mentioned QST measurement, the thin film magnetic head 1 does not have any defects in the fixed magnetic layer 13, the free magnetic layer 15, and the hard bias film 20, and the first DET Returns to the state before the measurement was performed. However, if any of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has a defect, it can be re-magnetized in the track width direction with a static magnetic field H1 smaller than the static magnetic field H2. The magnetization of the defective part remains in the height direction and does not return to the original.

  After the third magnetization step, the second DET measurement is performed under the same conditions as the first, and the output voltage of the thin film magnetic head 1 is obtained.

  Subsequently, the quality of the output characteristics is finally determined by comparing the first and second DET measurement results. Here, the measurement results to be compared are specifically the output voltage value, the asymmetry of the output voltage waveform, the average value of the peak voltage of the output voltage waveform, and the like.

  Since the first and second DET measurements are performed under the same conditions, the first and second measurement results should be essentially the same. However, when the first and second measurement results differ beyond the measurement error range, the second DET measurement is performed on the thin film magnetic head 1 in a state different from the first DET measurement. In other words, at least one of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has not changed and returned to its original state, and the thin film magnetic head 1 (the pinned magnetic layer 13, the free magnetic layer 15 In addition, it is estimated that defects are generated in the hard bias film 20). Therefore, in this embodiment, when the difference in the DET measurement result exceeds the measurement error range, the final determination is made that the output characteristic is bad, and if the difference is within the measurement error range, the output characteristic is good.

  Next, a method for evaluating a thin film magnetic head according to a second embodiment of the present invention will be described with reference to FIGS. 2, 3, 6 and 7. FIG. In the second embodiment, in order to further improve the evaluation accuracy, the output voltage characteristics of the thin-film magnetic head are measured three times with the process of strongly magnetizing in the height direction and then magnetizing in the track width direction between each measurement. In this embodiment, the quality of the output characteristics is determined based on the three measurement results. The output characteristic evaluation method of the second embodiment is the same as that of the first embodiment up to the second QST measurement step. Hereinafter, steps after the second QST measurement will be described.

  After the second QST measurement, as shown in FIG. 6, a strong static magnetic field H3 of 796 kA / m or more is applied to the thin film magnetic head 1 from the height direction (Y direction shown in the figure) orthogonal to the track width direction, and the hard bias film 20 is formed. After strongly magnetizing in the height direction, as shown in FIG. 2, a process of re-magnetizing the hard bias film 20 in the track width direction by applying a static magnetic field H1 to the thin film magnetic head 1 from the track width direction is executed at least once. . By this third magnetization step, the hard bias film 20 is returned to the first magnetization state of FIG. The static magnetic field H3 is opposite to the static magnetic field H2 applied in the height direction in the second magnetization step by 180 degrees and is set to the same magnitude as the static magnetic field H2. Since the static magnetic field H3 is extremely larger than the static magnetic field H1 when magnetized last time, the magnetization of the hard bias film 20 is easily oriented in the height direction. Accordingly, the magnetization direction of the free magnetic layer 15 is also aligned with the height direction. The magnitude of the static magnetic field H3 is practically about 796 kA / m or more and 1531 kA / m or less.

  Next, the third QST measurement is performed under the same conditions as the first and second times, and the output voltage-external magnetic field characteristic curve (VH curve) of the thin film magnetic head 1 is obtained.

  Subsequently, the quality of the output characteristics is determined by comparing the QST measurement results from the first time to the third time. More specifically, the difference between the first and second measurement results is calculated as first reference data, the difference between the first and third measurement results is calculated as second reference data, and the first reference data and The second reference data is compared to determine whether the output characteristics are good or bad. Here, the measurement results to be compared are the output voltage value, the asymmetry of the output voltage waveform (the waveform of the output voltage-external magnetic field characteristic curve), the average value of the peak voltage of the output voltage waveform, and the like.

  Since the QST measurement from the first time to the third time is performed under the same conditions, the first, second, and third measurement results should be essentially the same. Therefore, the calculated first reference data and second reference data should be the same. However, when the first reference data and the second reference data are different beyond the measurement error range, the thin film magnetic head in a state where the second or third QST measurement is different from the first QST measurement. 1, that is, at least one of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has not changed and returned to its original state, and the thin film magnetic head 1 (pinned magnetic layer 13, free magnetic layer 13 It is presumed that defects are generated in the magnetic layer 15 and the hard bias film 20). Therefore, in this embodiment, when the difference between the first reference data and the second reference data exceeds the measurement error range, it is determined that the output characteristic is bad, and when the difference is within the measurement error range, the output characteristic is good.

  FIG. 7 is a graph showing the difference in output voltage value of the output voltage waveform in the QST measurement from the first to the third time. In FIG. 7, the first reference data indicating the difference between the first and second measurement results is plotted with a rhombus marker, and the second reference data indicating the difference between the first and third measurement results is plotted with a square marker. Has been. In FIG. 7, the horizontal axis represents the average value (mV) of the voltage peak value of the output voltage waveform in the first QST measurement, and the vertical axis represents the voltage peak value of the output voltage waveform in the second or third QST measurement. The average value (mV) of each is shown. When the first reference data and the second reference data match, each marker is plotted on a straight line that satisfies the function y = x where x is the horizontal axis and y is the vertical axis. A marker greatly deviated from a straight line satisfying the function y = x shown by being surrounded by a dotted line in FIG. 7 indicates a thin film magnetic head having a defect that is determined to have an output characteristic defect.

  Subsequently, the thin film magnetic head determined to have poor output characteristics is excluded, and the first DET measurement is performed on the thin film magnetic head determined to have good output characteristics in the same manner as in the first embodiment described above. The output voltage of the head 1 is obtained.

  After the first DET measurement, as shown in FIG. 3, the hard bias film 20 is applied to the thin film magnetic head 1 by applying a strong static magnetic field H2 of 796 kA / m or more from the height direction (Y direction in the drawing) perpendicular to the track width direction. Is strongly magnetized in the height direction, and then a process of re-magnetizing the hard bias film 20 in the track width direction by applying a static magnetic field H1 to the thin film magnetic head 1 from the track width direction as shown in FIG. 2 is executed at least once. To do. By this fourth magnetization step, the hard bias film 20 is returned to the first magnetization state of FIG.

  Subsequently, the second DET measurement is performed under the same conditions as the first, and the output voltage of the thin film magnetic head 1 is obtained.

  After the second DET measurement, as shown in FIG. 6, a strong static magnetic field H3 of 796 kA / m or more is applied to the thin film magnetic head 1 from the height direction (Y direction in the drawing) orthogonal to the track width direction. Is strongly magnetized in the height direction, and then a process of re-magnetizing the hard bias film 20 in the track width direction by applying a static magnetic field H1 to the thin film magnetic head 1 from the track width direction as shown in FIG. 2 is executed at least once. To do. The static magnetic field H3 is opposite to the static magnetic field H2 applied in the height direction in the second magnetization step by 180 degrees and is set to the same magnitude as the static magnetic field H2. By this fifth magnetization step, the hard bias film 20 is returned to the first magnetization state of FIG.

  Subsequently, the third DET measurement is performed under the same conditions as the first and second times, and the output voltage of the thin film magnetic head 1 is obtained.

  Then, the quality of the output characteristics is determined by comparing the DET measurement results from the first time to the third time. More specifically, the difference between the first and second measurement results is calculated as first reference data, the difference between the first and third measurement results is calculated as second reference data, and the first reference data and The second reference data is compared to determine whether the output characteristics are good or bad. Here, the measurement results to be compared are the output voltage value, the asymmetry of the output voltage waveform (the waveform of the output voltage-external magnetic field characteristic curve), the average value of the peak voltage of the output voltage waveform, and the like.

  Since the DET measurement from the first time to the third time is performed under the same conditions, the measurement results of the first time, the second time, and the third time should be essentially the same. Therefore, the calculated first reference data and second reference data should be the same. However, when the first reference data and the second reference data are different beyond the measurement error range, the thin film magnetic head in a state where the second or third QST measurement is different from the first DET measurement. 1, that is, at least one of the pinned magnetic layer 13, the free magnetic layer 15, and the hard bias film 20 has not changed and returned to its original state, and the thin film magnetic head 1 (pinned magnetic layer 13, free magnetic layer 13 It is presumed that defects are generated in the magnetic layer 15 and the hard bias film 20). Therefore, in the present embodiment, when the difference between the first reference data and the second reference data exceeds the measurement error range, the final determination is made that the output characteristic is bad and if the difference is within the measurement error range, the output characteristic is good.

  FIG. 8 is a graph showing the correlation between the QST measurement result and the DET measurement result, where the horizontal axis x is the output voltage fluctuation range (%) in the second and third DET measurements, and the vertical axis y is the first. The fluctuation width (%) of the output voltage in the second and third QST measurements is shown. It can be seen from the graph of FIG. 8 that the DET measurement result and the QST measurement result correspond 1: 1, that is, the correlation is high.

  According to each of the embodiments described above, the hard bias film is once strongly magnetized in the height direction and then magnetized in the track width direction during the first and second (and third) measurement steps. Since the soot magnetizing step is executed, the thin film magnetic head 1 (the fixed magnetic layer 13, the free magnetic layer 15, the hard bias film) is measured when the first and second (and third) measurement results are different. 20) There is a possibility that a defect has occurred in the device, and it is determined that the output characteristic is defective. Thereby, a defective GMR head can be excluded in advance, and degradation and instability that cannot be detected by the conventional QST measurement and DET measurement can be suppressed. In addition, the yield of the hard disk on which the thin film magnetic head determined to have good output characteristics in this embodiment is also improved.

  Further, in each of the above embodiments, the final pass / fail judgment is performed by performing the DET measurement after the QST measurement. However, since the QST measurement and the DET measurement are correlated as shown in FIG. The structure which performs only one side may be sufficient. If only QST measurement that can be measured without using an actual magnetic recording medium is performed, it is possible to more easily realize high-accuracy output characteristic evaluation.

It is sectional drawing which shows one Embodiment of the thin film magnetic head which is the evaluation object of this invention method. It is a conceptual diagram explaining the process of magnetizing a hard bias film | membrane in a track width direction. It is a conceptual diagram explaining the process of magnetizing a hard bias film in a height direction. It is a graph which shows the average value of the voltage peak value of the output voltage waveform in the QST measurement of the 1st time and the 2nd time. It is a graph which shows the difference of the asymmetry of the output waveform in the QST measurement of the 1st time and the 2nd time. FIG. 4 is a conceptual diagram for explaining a process of magnetizing a hard bias film in the height direction in a direction opposite to that of FIG. 3 by 180 degrees. It is a graph which shows the difference of the output voltage value of the output voltage waveform in the QST measurement from the 1st time to the 3rd time. It is a graph which shows the correlation of a QST measurement result and a DET measurement result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thin-film magnetic head 11 Seed layer 12 Antiferromagnetic layer 13 Fixed magnetic layer 14 Nonmagnetic conductive layer 15 Free magnetic layer 16 Cap layer 20 Hard bias film 21 Bias base film 30 Electrode layer X Track width direction Y Height direction Z Stacking direction

Claims (12)

This is a method for evaluating the output characteristics of a thin-film magnetic head having hard bias films on both sides in the track width direction of a spin valve film formed by laminating an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. And
A first magnetization step of magnetizing the hard bias film in the track width direction;
A first measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field;
After the hard bias film is magnetized in the height direction perpendicular to the track width direction, a process of further magnetizing in the track width direction is executed at least once, and the hard bias film is magnetized in the track width direction. Two magnetizing steps;
A second measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field under the same conditions as the first time;
A determination step of comparing the first and second measurement results to determine the quality of the output characteristics of the thin film magnetic head;
A method for evaluating a thin film magnetic head, comprising: 2. The method for evaluating a thin film magnetic head according to claim 1, wherein the magnetic field in the height direction in the second magnetization step is stronger than the magnetization magnetic field in the first magnetization step. . 3. The thin film magnetic head evaluation method according to claim 1, wherein in the determination step, at least an asymmetry of an output voltage value of the thin film magnetic head and an output waveform of the thin film magnetic head is obtained as a measurement result of the measurement step. Evaluation method of thin film magnetic head using one of them. 4. The thin film magnetic head evaluation method according to claim 1, wherein the measurement step is a static measurement performed in a state where the thin film magnetic head is stationary without using a magnetic recording medium. 5. Magnetic head evaluation method. 4. The thin film magnetic head evaluation method according to claim 1, wherein the measurement step is a dynamic measurement performed in a state where the thin film magnetic head is floated on a magnetic recording medium. 5. Head evaluation method. This is a method for evaluating the output characteristics of a thin-film magnetic head having hard bias films on both sides in the track width direction of a spin valve film formed by laminating an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. And
A first magnetization step of magnetizing the hard bias film in the track width direction;
A first static measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field in a state where the thin film magnetic head is stationary without using a magnetic recording medium;
After the hard bias film is magnetized in the height direction perpendicular to the track width direction, a process of further magnetizing in the track width direction is executed at least once, and the hard bias film is magnetized in the track width direction. Two magnetizing steps;
A second static measurement step of measuring an output characteristic of the thin-film magnetic head by applying an alternating electric field under the same conditions as the first time;
A determination step of comparing the first and second static measurement results to determine the quality of the output characteristics of the thin film magnetic head;
A screening process for extracting the thin film magnetic head judged to have good output characteristics, excluding the thin film magnetic head judged to have poor output characteristics,
A first dynamic measurement step of dynamically measuring an output characteristic of the thin film magnetic head by applying an alternating electric field in a state where the extracted thin film magnetic head is floated on a magnetic recording medium;
After the hard bias film is magnetized in the height direction orthogonal to the track width direction, a process of further magnetizing in the track width direction is performed at least once, and the hard bias film is magnetized in the track width direction. 3 magnetizing steps;
A second dynamic measurement step of measuring an output characteristic of the thin-film magnetic head by applying an alternating electric field under the same conditions as the first time;
A final determination step of finally determining the quality of the output characteristics of the thin film magnetic head by comparing the first and second dynamic measurement results;
A method for evaluating a thin film magnetic head, comprising: This is a method for evaluating the output characteristics of a thin-film magnetic head having hard bias films on both sides in the track width direction of a spin valve film formed by laminating an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. And
A first magnetization step of magnetizing the hard bias film in the track width direction;
A first measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field;
After the hard bias film is magnetized in the height direction perpendicular to the track width direction, a process of further magnetizing in the track width direction is executed at least once, and the hard bias film is magnetized in the track width direction. Two magnetizing steps;
A second measurement step of measuring an output characteristic of the thin film magnetic head by applying an alternating electric field under the same conditions as the first time;
After the hard bias film is magnetized in the height direction perpendicular to the track width direction, a process of further magnetizing in the track width direction is executed at least once, and the hard bias film is magnetized in the track width direction. 3 magnetizing steps;
A third measurement step of measuring an output characteristic of the thin-film magnetic head by applying an alternating electric field under the same conditions as the first and second times;
Calculating a difference between the first and second measurement results as first reference data, and calculating a difference between the first and third measurement results as second reference data;
A determination step of comparing the calculated first reference data and second reference data to determine whether the output characteristics of the thin film magnetic head are good or bad;
A method for evaluating a thin film magnetic head, comprising: 8. The method of evaluating a thin film magnetic head according to claim 7, wherein a magnetizing magnetic field in the height direction in the second magnetizing step and the third magnetizing step is greater than a magnetizing magnetic field in the first magnetizing step. Evaluation method for strong thin-film magnetic heads. 9. The method of evaluating a thin film magnetic head according to claim 7, wherein a magnetization magnetic field in the height direction in the second magnetization step and a magnetization magnetic field in the height direction in the third magnetization step are: A method for evaluating a thin film magnetic head having the same strength and a magnetic field direction of 180 degrees opposite. 10. The thin film magnetic head evaluation method according to claim 7, wherein in the determination step, an output voltage value of the thin film magnetic head and an output of the thin film magnetic head are obtained as a measurement result of the measurement step. A method of evaluating a thin film magnetic head using at least one of waveform asymmetry. 11. The thin film magnetic head evaluation method according to claim 7, wherein the measurement step is a static measurement performed in a state where the thin film magnetic head is stationary without using a magnetic recording medium. Magnetic head evaluation method. 11. The thin film magnetic head evaluation method according to claim 7, wherein the measurement step is a dynamic measurement performed in a state where the thin film magnetic head is floated on a magnetic recording medium. Head evaluation method.

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