Abstract: A method of calculating an amplitude decay rate of a magnetic storage medium. The method involves (a) writing a test track to the magnetic storage medium and measuring the initial amplitude of the test track to obtain a reference amplitude; (b) performing a DC erase on the test track; (c) measuring and storing the test track amplitude after step (b) together with a time at which the measurement was made; (d) writing a reference track; (e) measuring and storing the reference track amplitude after step (d); (f) repeating steps (b) to (e) until a DC erase amplitude decay rate has been established; and (g) calculating a normal amplitude decay rate for the magnetic storage medium from the DC erase amplitude decay rate.

Abstract: A disc stabilizer for use in a spin-stand tester having a spindle motor for rotating a disc is provided. The spin-stand tester is capable of positioning a transducing head adjacent a first surface of the disc. The disc stabilizer includes a vacuum plate coupled to a spindle of the spindle motor. The vacuum plate has a top surface and a bottom surface opposite the top surface. At least one of the top and the bottom surfaces is a grooved surface including multiple vacuum channels. The grooved surface is substantially in contact with a second surface of the disc. Vacuum distributed through the multiple vacuum channels of the grooved surface is applied directly to the second surface of the disc, thereby holding the disc in place.

Abstract: An apparatus and method for detecting and marking delamination defects on thin film disks are disclosed. The apparatus includes a read/write (R/W) head and a burnishing head mounted on separate arms that access the disk while spinning on the test stand. The controller uses the R/W head to perform an initial magnetic test of selected areas on the disk to establish an initial defect map. The burnish head is then flown over the surface for an extended time to accelerate and open up the latent delamination defects by impacting protruding material. The R/W head is then used to perform a second magnetic test which is compared against the first test to identify the delamination defects which have been developed by the burnishing. The delamination defects are then marked with a magnetic pattern which aids in optically locating the defect during subsequent failure analysis.

Abstract: A method and system for detecting electrostatic noise in a magneto-resistive head which may be caused by a plurality of conditions manifesting in the frequency domain as either an amplitude spike or an unstable baseline. In one embodiment, the signals generated by the head when reading a DC-erased track are compared. When viewed in the frequency domain the spectrum gap between the signals is used to determine if the head being tested suffers from defects causing an unstable baseline or from defects causing an amplitude spike.

Abstract: A method and apparatus are provided for testing a head to be used in a disc drive. The method is performed in a spin-stand and includes steps of positioning a head over a radial position on a disc, reading test data from a track at the radial position, reading servo data from the track, and using the servo data to position the head at a desired location within the track. The apparatus for practicing this method includes a disc capable of spinning, a positioning system capable of establishing a position for a head relative to the disc, a servo circuit capable of converting a servo signal into a position value, and a feedback circuit capable of controlling the positioning system based on the position value.

Abstract: A method and system for the rapid automatic screening of GMR heads for Barkhausen noise during production. This system rapidly and repeatedly measures associated noise in a GMR head subjected to a smoothly-varying external transverse magnetic field. The repeated Transverse Magnetic-field Excited Noise (TMEN) measurements are automatically sorted into bins to form a histogram, which is then automatically evaluated to develop TMEN range and weighted sum measures, which are then compared with predetermined standards for automatic acceptance or rejection of the GMR head under test. The GMR sensor Barkhausen noise is quantified through the use of a bandpass filter to remove all direct sensor responses, leaving only the noise signals, which are then repeatedly sampled to develop valid statistical Barkhausen noise measures suitable for automated analysis.

Abstract: A testing device tests a LCD driver LSI which incorporates a multiple number of D/A converters and outputs voltages from the D/A converters via associated output terminals. A voltage meter measures a multiple levels of tonal voltages output from the first output terminal and calculates the differential voltage value between each measured voltage and the associated expected voltage. Each differential amplifier has an input for receiving the output voltage output from the first output terminal in common and another input for receiving the output voltage output from one output terminal other than the first output terminal. A comparator receives the amplified differential voltages output from the plural differential amplifiers and checks whether the amplified differential voltages from the differential amplifiers fall within given voltage ranges, receptively.

Abstract: The present invention relates to a head tester for testing heads having a read element and a write element. The tester comprises a substrate on which a read coil is positioned to be sensitive to the write element of the head. A write coil is also formed on the substrate and this coil is positioned such that the read element of the head to be tested is sensitive to the write coil.

Abstract: The support that bears and positions the head in a head holding apparatus is further supported by a heat-compensating member, so that when the support is expanded by the heat source of the head holding apparatus, the heat-compensating member expands in the direction opposite to the direction of expansion of the support. Moreover, supplying of heat to the support and heat-compensating member is further alleviated by insulating said heat source with an insulating material. The amount of displacement of the recording element per unit of time with exposure to heat is controlled by the above-mentioned structure and effects.

Abstract: In a magnetic head measuring apparatus for measuring a magnetic head, an amplitude-modulated electric current whose amplitude is modulated by a specified carrier wave frequency and modulation frequency is applied to a magnetic head.

Abstract: A method and system for the rapid automatic screening of GMR heads for Barkhausen noise during production. This system rapidly and repeatedly measures associated noise in a GMR head subjected to a smoothly-varying external transverse magnetic field. The repeated Transverse Magnetic-field Excited Noise (TMEN) measurements are automatically sorted into bins to form a histogram, which is then automatically evaluated to develop TMEN range and weighted sum measures, which are then compared with predetermined standards for automatic acceptance or rejection of the GMR head under test. The GMR sensor Barkhausen noise is quantified through the use of a bandpass filter to remove all direct sensor responses, leaving only the noise signals, which are then repeatedly sampled to develop valid statistical Barkhausen noise measures suitable for automated analysis.

Abstract: A process for resetting or initially establishing the magnetic orientation of one or more spin valves in a magnetoresistive read head with improved robustness. The spin valve includes subcomponents such as an antiferromagnetic layer, a ferromagnetic pinned layer, a conductive layer, a free layer, and a hard bias layer. A first external magnetic field is first applied to the spin valve sensor, this field having a first orientation relative to the spin valve sensor. During application of the first external magnetic field, a pulse of electrical current is directed through the spin valve sensor in a first direction, preferably parallel to the magnetic orientation of the external field. The current waveform brings the antiferromagnetic layer of the spin valve past its blocking temperature, freeing its magnetic orientation. The first external field exerts a robust bias upon the antiferromagnetic layer in the desired direction.

Abstract: In fabricating magnetic heads on a wafer surface, magnetoresistive sensors having two different stripe heights and the same stripe width are formed. Additionally, two different electronic lapping guides (ELGs) having different stripe heights and the same stripe width are also formed. While the design widths and heights of the sensors and ELGs are known, the actually fabricated widths and heights of the sensors and ELGs is unknown, due to the windage in the fabrication process. In the present invention, to determine the actual track width of the sensors, the change in electrical resistance of the sensors and ELGs is experimentally determined during the application of a magnetic field to the sensors and ELGs. Through a mathematical analysis, the actual track width of the fabricated sensors is determined utilizing the design widths and heights of the sensors and ELGs, together with the experimentally determined changes in electrical resistance of the sensors and ELGs.

Abstract: A method for forming metrology structures on a wafer on which magnetic transducers are being fabricated is disclosed. The metrology structures have a measurable electrical resistance which is an accurate surrogate for a physical dimension of a structure of the magnetic transducer, such as a pole piece tip. The metrology structure is preferably a resistor with pads usable with a four point probe. The resistor is preferably formed by creating a sacrificial pole piece structure over a pad of resistive material. The narrow dimension of the pole tip is then used as a mask to replicate the width of the pole tip in the resistive material through a milling process which removes resistive material outside of the masked area of the resistor pad. Control structures with unmilled pads of resistive material are formed along with the metrology structures to provide the sheet resistance of the pads prior to milling.

Abstract: Disclosed is a lapping monitor element that is juxtaposed with a magnetic transducer element having a magnetoresistance effect film to determine the lapping position upon lapping the element height of the magnetic transducer element to a predetermined dimension, the lapping monitor element comprising a resistance film to be resistance measured, the resistance film being a metal film of nonmagnetic transition metal or of alloy composed mainly of nonmagnetic transition metal, or a multilayered film where two or more such metal films are laid one upon another, thereby making it possible to extremely stabilize the ELG sensor resistance measured values upon lapping as well as to provide a high accuracy MR height control.

Abstract: This invention presents a method and system for testing a disc drive head usable with a disc drive head testing device. The steps for this include determining an unknown electrical property of the head testing device. This is done by generating output signals at the output stage. The testing device property is then computed by solving for the unknown electrical property based on the output signals generated for each of the known test devices. For each disc drive head under test, the head is coupled to the input lead and exposed to a stored magnetic data pattern to generate a read signal at the input lead. The measured difference affects the generated read output signal. The read output signal is adjusted based on the testing device property and the measured property to compensate for differences in the measured property.

Abstract: A method and apparatus are provided for testing a microactuator that forms part of a suspension assembly in a disc drive. The method and apparatus test the microactuator before placing the suspension assembly in a disc drive. In the invention, the head is positioned over a track on a disc based in part on servo information read from the disc. At least one input signal is then applied to at last one microactuator on the suspension assembly. Servo information is then read from the disc to determine a change in the position of the head. By comparing the change in the position of the head to the input signal applied to the microactuator, a performance characteristic of a microactuator can be determined.

Abstract: A method and computer program to calculate a reproduction track width of an MR head. This method begins by subdividing the magnetic domain control layer of an MR element and lead conductors into several polyhedral elements. Thereafter, electric potentials are calculated for each of the polyhedral elements based on the resistance at each layer. A current density is determined for each of the polyhedral elements based on the calculated electric potentials. The current densities are integrated to calculate an initial resistance value. Further, the resistance of a local block is changed by a predetermined amount. The electric potential is calculated for each of the polyhedral elements, current density is acquired, and the acquired current densities is calculated to determine a resistance value. Finally, the reproduction track width is obtained based on the initial acquired resistance value and the acquired resistance value.

Abstract: Side-reading of an abutted-junction magnetic transducer is measured by constructing at least one microtrack having a transition density. The transducer is moved relative to the microtrack to identify a plurality of positions of the transducer relative to the microtrack where the transducer provides a predetermined response. The side-reading distance of the transducer is identified from the plurality of positions. In one embodiment, a plurality of microtracks are constructed during different iterations, each having a different transition density, and the positions of the transducer are identified during each iteration relative to the respective microtrack. In another embodiment, the selected transition density has a fundamental frequency, and the position of the transducer is identified relative to the microtrack where the transducer provides the predetermined response at each of a plurality of harmonic frequencies of the fundamental frequency.

Abstract: A method to test an instability of a magneto-resistive (MR) head. The instability is tested by first writing a signal onto a track. The junctions of the MR head are aligned with various track edges and the head characteristics are then measured. The characteristics may include determining a maximum amplitude covarian and a maximum base line popping noise.

Abstract: A head testing apparatus is provided for testing a data recording head. The apparatus includes a test volume, a magnetic field source, a holder and a thermoelectric source. The test volume is adapted to receive the head, and the magnetic field source is positioned to generate a magnetic field within the test volume. The holder is adapted to hold the head and position the head within the test volume. The thermoelectric source is positioned to contact the head when the head is positioned within the test volume by the holder.

Abstract: A method and apparatus for characterizing asymmetries of a magneto-resistive type head in proximity to a magnetic media such as a magnetic disk of a hard disk drive. The method includes using the magneto-resistive type head to read a continuous signal from the magnetic media to provide a read back signal. Energies contained in the read back signal which occur in excess of a predetermined threshold for the positive and negative portions of the read back signal are then determined. The energies may be determined by accumulating sampled signal values from the read back signal in registers during times at which the read back signal exceeds the threshold.

Abstract: A test simulation circuit includes a simulated read/write head with a magnet shield and a magnetoresistive sensor exposed at a lapped surface. The test simulation circuit also includes first and second electrical test path connected respectively to the magnet shield and the magnetoresistive sensor. The second electrical test path is electrically isolated from the first electrical test path.

Abstract: A method for testing a thin-film magnetic head with a MR read head element includes a step of applying a low-frequency or DC external magnetic field to the thin-film magnetic head from a stationary magnetic field generation unit, a step of executing a high-frequency amplification of an output from the MR read head element under the application of the external magnetic field to provide a high-frequency amplified signal, a step of deriving only a high-frequency component from the high-frequency amplified signal to provide a high-frequency component signal, and a step of judging whether the thin-film magnetic head occurs a noise or not by using the high-frequency component signal.

Abstract: A head testing apparatus is provided for testing a magnetic data recording head. The apparatus includes a test volume adapted to receive the magnetic data recording head and a magnetic field source positioned to generate a magnetic field within the test volume. A Hall sensor is positioned relative to the test volume and has bias current input terminals, voltage output terminals, an operating temperature and an impedance between the bias current input terminals, which varies with the operating temperature. A bias current source is electrically coupled to the bias current input terminals and is adapted to provide a bias current, which is modulated based on the impedance of the Hall sensor.

Abstract: A method to test an instability of a magneto-resistive (MR) head. The instability is tested by first writing a signal onto a track. The junctions of the MR head are aligned with various track edges and the head characteristics are then measured. The characteristics may include determining a maximum amplitude covarian and a maximum base line popping noise.

Abstract: A system for testing the read/write head elements of a head stack assembly (“HSA”). A completed HSA is placed in the test apparatus. Test probes are aligned and placed in electrical contact with the electrical leads coming from each head element, between the head elements and the preamplifier. The HSA is then placed in a changing magnetic field. A low frequency magnetic field can be applied to test the head elements. The changing magnetic field induces electrical signals within the head elements. By analyzing these electrical signals, the condition and characteristics of the each head element can be determined.

Abstract: A method for manufacturing a disk drive includes assembling the head disk assembly in a clean room, performing servo writing upon the head disk assembly in the clean room, and performing a head disk assembly test upon the head disk assembly in the clean room. The head disk assembly is then connected to the controller printed circuit board assembly to form a drive-under-test. The drive-under-test is then transported to an integrated test system and electrically connected thereto. The integrated tests system then performs substantially all of the required manufacturing tests upon the drive-under-test, thereby substantially reducing the labor and floor space associated therewith.

Abstract: A method for magnetically measuring the magnetic read width (MRW) of magnetic recording heads having a track width that is equal or smaller than the wavelength of visible light is provided. The heads comprise a magnetic read head spin valve sensor and the magnetic read head sensor signal is used to derive an unknown track width from comparing to the sensor response of aknown track width. Using this method, track widths in the regions at the wavelength of light and below (<500 nm) can be directly measured without destroying the respective sensor material.

Abstract: Assuming that a distance between an upper shield layer and a lower shield layer in an area, which overlaps only a first electrode layer, but does not overlap a second electrode layer, is G1s, and a distance between the upper shield layer and the lower shield layer at a position in alignment with a center of a multilayered film is G1c, a difference in value between G1s and G1c is set to be not larger than a predetermined value, whereby an effective track (read) width can be reduced.

Abstract: A magnetic head measuring apparatus executes measurement with respect to at least one measurement point on a recording head. The apparatus includes a probe having a magnetic substance, a vibrator which vibrates the probe above the at least one measurement point, a first signal generator which supplies a drive signal to the vibrator, a second signal generator which supplies a current containing a direct current and an alternate current to the recording head to generate a magnetic field from the recording head, a detector configured to detect a signal corresponding to a force interaction that acts on the probe due to the magnetic field generated from the recording head in accordance with the current supplied by the second signal generator, and a measurement unit which measures current dependence of the magnetic field of the recording head from the signal detected by the detector.

Abstract: There is provided an apparatus and method for controlling a disc drive and, more particularly, an apparatus and method for restoring stability to a head of a hard disc drive, so that instability in a magneto resistive (MR) sensor of the disc drive can be restored through an electric shock. Instability of the MR head, i.e. incorrect alignment of the domain of the MR head, is determined by a bit error rate (BER) test and channel statistical measurement (CSM) test, and If instability of the MR bead is determined, the MR head is restored by applying electric shocks thereto. Therefore, the apparatus and method have advantages in that manufacturing process inferiority rate due to instability of head in a hard disc drive can be reduced, yield can be improved and the defect rate can be improved.

Abstract: There is disclosed a magnetic field characteristics evaluation apparatus for turning off a switching signal, measuring the surface of a magnetic field generating member in a magnetized state by AFM, and storing AFM signal together with a position signal corresponding to a scanning position in a memory to display a surface configuration based on the AFM signal. Subsequently, the switching signal is turned on, the magnetic head is set to a magnetized state, the AFM signal is referred to, the magnetic head surface is measured by MFM, and MFM signal together with the position signal corresponding to the scanning position are stored in the memory to display a surface magnetic field distribution based on the MFM signal. Therefore, it is possible to accurately specify, from the surface, a position in which the magnetic field is generated.

Abstract: A method for testing a composite type magnetic head having a MR element and an inductive element includes a current application step of applying a current to the inductive element, with applying no external magnetic field to the magnetic head, and a measurement step of measuring output characteristics of the MR element after the current application step is finished.

Abstract: A device for calibrating drag test drives comprises a disk drive unit, a non conductive, non magnetic disk, and a magnet placed substantially planar to the non magnetic disk wherein the disk can spin in the disk drive through a magnetic field produced by the magnet. The device also comprises a current measuring device wherein the device measures the amount of current the disk drive motor draws while spinning the disk.

Abstract: A method and apparatus are disclosed for characterizing asymmetries of a magneto-resistive type head (18) in proximity to a magnetic media (40) such as a magnetic disk of a hard disk drive (12). The method includes using the magneto-resistive type head (18) to read a continuous signal from the magnetic media (40) to provide a read back signal (110, 112). Energies contained in the read back signal which occur in excess of a predetermined threshold (111, 58) for the positive (110) and negative (112) portions of the read back signal are then determined. The energies may be determined by accumulating sampled signal values from the read back signal in registers (78) during times at which the read back signal exceeds the threshold (111, 58).

Abstract: In an apparatus for detecting foreign particles adhered to a magnetic head, a current error rate of data read from the magnetic head is calculated, and an accumulative error rate of data read from the magnetic head is calculated. Then, the current error rate is compared with the accumulative error rate to determine whether or not foreign particles are adhered to the magnetic head.

Abstract: There is disclosed an apparatus for locating a defect on an MR head without destroying it, if such a defect is present. The MR head has a head element, write electrode terminals, read electrode terminals, and a head electrode connected with the head element. The apparatus has a power supply and an OBIC amplifier. The power supply is connected with one of the three electrodes. The OBIC amplifier is connected with another electrode. The apparatus further includes a laser that emits a laser beam to a region containing the head element. A reflection image based on the reflected beam from the illuminated region and an internal photoelectric effect image based on a signal produced by electrical carriers induced by the internal photoelectric effect are displayed in a superimposed manner on a color CRT. This permits an operator to know where a defect is present on the MR head, if such a defect is present.

Abstract: A plurality of magnetic head devices are placed on different scanning regions in the radial direction of a disk-shaped recording medium. Each scanning region is slightly displaced from each of the other scanning regions in the radial direction of the recording medium. The plurality of magnetic head devices is tested.

Abstract: A testing apparatus for a magnetic head or a magnetic disk, includes a magnetic disk; a magnetic head moving mechanism which holds a magnetic head and which moves the magnetic head to a predetermined position in a radial direction of the magnetic disk; a movement mechanism control device for driving the magnetic head moving mechanism, wherein the movement mechanism control device moves the magnetic head moving mechanism to a predetermined radial position corresponding to position data; a read/write control device for writing a predetermined magnetic signal on the magnetic disk using the magnetic head, and for reading a magnetic signal of the magnetic disk using the magnetic head; and a memory for storing therein position data embedded in a data surface of the magnetic disk, extracted from the magnetic signal which is read by the read/write control device. A testing method is also disclosed.

Abstract: A magnetic force sensor detects a magnetic force of a magnetic sample having a given magnetization direction. The magnetic force sensor comprises a magnetic probe having a tip portion. The tip portion has an electrolytically plated film of hard-magnetic material effective to maintain the magnetization direction of the probe constant and parallel to the given magnetization direction of the sample.

Abstract: This invention presents a method and system for testing a disc drive head usable with a disc drive head testing device. The steps for this include determining an unknown electrical property of the head testing device. This is done by generating output signals at the output stage. The testing device property is then computed by solving for the unknown electrical property based on the output signals generated for each of the known test devices. For each disc drive head under test, the head is coupled to the input lead and exposed to a stored magnetic data pattern to generate a read signal at the input lead. The measured difference affects the generated read output signal. The read output signal is adjusted based on the testing device property and the measured property to compensate for differences in the measured property.

Abstract: A method and apparatus for providing predictive failure analysis using the resistance of a sensor such as a MR, GMR, spin valve or wear sensor. A baseline measurement of resistance for at least one sensor of a disk drive is obtained, subsequent measurements of resistance for the at least one sensor of a disk drive are periodically obtained and the subsequent measurements and the baseline measurement to identify a detrimental change to the at least one sensor are processed. The processing further includes comparing a subsequent resistance measurement for the at least one sensor to the baseline measurement of resistance for the at least one sensor to detect a head/disk interface problem and flagging the file for corrective action when the head/disk interface problem is detected. Alternatively, the processing further includes determining a change in stripe height based upon the difference between the baseline measurement of resistance and the subsequent measurement of resistance.

Abstract: A method comprises manufacturing a read/write head for a disk drive; then testing the read/write head; and then mounting the read/write head to a suspension only after the testing step indicates that the read/write head is not defective. The testing may be performed by writing information to and reading information from a non-disc shaped media paddle that is caused to move back and forth with respect to the read/write head in oscillatory fashion.

Abstract: A current which will change an initial magnetization state of a shield layer for a MR element is applied to an inductive element, and output characteristics of the MR element is measured.

Abstract: A test simulation circuit includes a simulated read/write head with a magnet shield and a magnetoresistive sensor exposed at a lapped surface. The test simulation circuit also includes first and second electrical test path connected respectively to the magnet shield and the magnetoresistive sensor. The second electrical test path is electrically isolated from the first electrical test path.

Abstract: A method for testing a thin-film magnetic head with a MR read head element includes a step of applying a low-frequency or DC external magnetic field to the thin-film magnetic head from a stationary magnetic field generation unit, a step of executing a high-frequency amplification of an output from the MR read head element under the application of the external magnetic field to provide a high-frequency amplified signal, a step of deriving only a high-frequency component from the high-frequency amplified signal to provide a high-frequency component signal, and a step of judging whether the thin-film magnetic head occurs a noise or not by using the high-frequency component signal.

Abstract: A method for non-destructive measurement of dynamic coercivity is disclosed. In this method, magnetic media is DC erased by applying a forward DC magnetic field to the magnetic media such that the magnetic moments in the magnetic media are substantially aligned. A specified number of reversed magnetic field pulses are then applied to the magnetic media in a direction opposite to the forward DC magnetic field, wherein the intensity of the reversed magnetic field pulses is less than the remanent coercivity of the magnetic media. The broadband medium noise of the magnetic media is measured. The intensity of the reversed magnetic field pulses is then repeatedly and incrementally increased and applied to the write head for the specified number of pulses, the intensity of the reversed magnetic field pulses eventually exceeding the remanent coercivity of the magnetic media. For each intensity level of the reversed magnetic field pulses, the broadband medium noise is again measured.

Abstract: An apparatus for measuring a characteristic of a specimen, includes a probe for scanning a surface of the specimen in a noncontacting state, a vibrating unit for vibrating the probe, an excitation field generating unit for generating an amplitude modulation signal which is amplitude-modulated with a modulation frequency and a carrier frequency and producing an excitation field at the surface of the specimen on the basis of the generated amplitude modulation signal, and a measuring unit for measuring a force interaction between the probe and the specimen caused by the excitation field generated at the surface of the specimen.

Abstract: A system for testing the read/write head elements of a head stack assembly (“HSA”). A completed HSA is placed in the test apparatus. Test probes are aligned and placed in electrical contact with the electrical leads coming from each head element, between the head elements and the preamplifier. The HSA is then placed in a changing magnetic field. A low frequency magnetic field can be applied to test the head elements. The changing magnetic field induces electrical signals within the head elements. By analyzing these electrical signals, the condition and characteristics of the each head element can be determined.