Abstract: A Magnetoresistive Random Access Memory (MRAM) device is tested using a high repetition test that detects one or more low-likelihood failures, such as a failure to properly switch between a high or low resistive state. A series of write and read operations are performed for a large number of test cycles at high frequency. A first tier measurement is used to determine if a switching failure occurred, e.g. by comparing the read signal to target level(s) after each operation. When a switching failure event is detected, a second tier measurement is used to measure and store switching performance parameters, for example, the value of the read signal, while the MRAM device is in a failure state. The high frequency testing may be paused during the second tier measurements. Additional performance parameters may be measured during the second tier measurements.

Abstract: A diamond probe is suitable to be attached to an Atomic Force Microscope and is created with a tip that incorporates a one or more Nitrogen Vacancy (NV) centers located near the end of the tip. The probe arm acts as an optical waveguide to propagate the emission from the NV center with high efficiency and a beveled end directs excitation light to the NV center and directs photoluminescence light emanating from the NV center into the probe arm. The light source (or a portion of the light source), a detector, as well as an RF antenna, if used, may be mounted to the probe arm. The probe with integrated components enable excitation of photoluminescence in the NV center as well as optically detected Electron Spin Resonance (ODMR) and temperature measurements, and may further serve as a light probe utilizing the physical effect of Stimulated Emission Depletion (STED).

Abstract: A diamond probe is suitable to be attached to an Atomic Force Microscope and is created with a tip that incorporates a one or more Nitrogen Vacancy (NV) centers located near the end of the tip. The probe arm acts as an optical waveguide to propagate the emission from the NV center with high efficiency and a beveled end directs excitation light to the NV center and directs photoluminescence light emanating from the NV center into the probe arm. The probe tip is scanned over an area of a sample with an electric charge, such as a field effect transistor or flash memory. Optically Detected Spin Resonance (ODMR) is measured as the probe tip is scanned over the area of the sample, from which a characteristic of the area of the sample with the electric charge may be determined.

Abstract: A diamond probe is suitable to be attached to an Atomic Force Microscope and is created with a tip that incorporates a one or more Nitrogen Vacancy (NV) centers located near the end of the tip. The probe arm acts as an optical waveguide to propagate the emission from the NV center with high efficiency and a beveled end directs excitation light to the NV center and directs photoluminescence light emanating from the NV center into the probe arm. The light source (or a portion of the light source), a detector, as well as an RF antenna, if used, may be mounted to the probe arm. The probe with integrated components enable excitation of photoluminescence in the NV center as well as optically detected Electron Spin Resonance (ODMR) and temperature measurements, and may further serve as a light probe utilizing the physical effect of Stimulated Emission Depletion (STED).

Abstract: A read head is tested by measuring the thermal magnetic fluctuation noise spectrum. A non-uniformity in the magnetic field of the free layer is produced and the thermal magnetic fluctuation noise spectrum is measured, with and/or without an external magnetic field applied. A peak in the thermal magnetic fluctuation noise spectrum can be used to derive the desired dimension of the free layer, such as track width and stripe height. The resulting measurement may then be fed back into the process control for the production of the read heads if desired. Additionally, the stiffness of the free layer and the strength of the reference layer may be determined using ferromagnetic resonance peaks in the thermal magnetic fluctuation noise spectrum.

Abstract: A crystal film with nitrogen vacancy centers is placed in close proximity to a photon emitter. Excitation illumination is produced to cause the nitrogen vacancy centers to produce photoluminescence. Illumination is produced by the photon emitter, which may be near field or far field and which quenches the photoluminescence intensity using an effect known as Stimulated Emission Depletion (STED). The quenching caused by the photon emitter is detected and analyzed to determine characteristics of the photon emitter. The analysis takes into account the characteristic dependence of the STED on the depletion light power, i.e. the photon source, and a spatial distribution of the light intensity. The analysis may be applied to spatially resolved measurements or an integral value of the photoluminescence quenching. The analysis may determine characteristics such as peak power, power scaling factor, and FWHM of the illumination profile of the photon emitter.

Abstract: A crystal film with one or more nitrogen vacancy centers is placed in close proximity to a recording head. A magnetic field or heat produced by the recording head as well as excitation illumination and an excitation field is applied to the crystal film. The magnetic field produced by the recording head, the heat produced by a thermal device on the recording head, and/or the excitation field may be varied. A confocal microscope or wide-field microscope optically detects a decrease in a spin dependent photoluminescence in response to the magnetic field or heat, excitation field and excitation illumination caused by electron spin resonance (ESR) of the at least one nitrogen vacancy center to measure Optically Detected Spin Resonance (ODMR). A characteristic of the recording head is determined using the ODMR.

Abstract: A testing device tests a magnetic head with a read head structure including a read head element while applying an external magnetic field to the magnetic head. The testing device receives signals from the read head element and processes the signals to generate a spectral power density for the signals. The spectral power density is characterized for at least one frequency range. The characterization of the spectral power density is used to determine a characteristic of noise from the read head structure. The signals from the read head may be received with different applied magnetic fields and/or before or while thermally exciting the magnetic head. Additionally, a histogram of the signals may be generated and used to determine a second characteristic of the noise.

Abstract: A write head is tested by measuring the effect that magnetic fields have on the inductance of the write head. For example, a perpendicular write head may be placed in a magnetic field with a first angle, e.g., non-parallel and non-perpendicular, to the air bearing surface and the inductance is measured. After altering the angle of the magnetic field the inductance is again tested. In another embodiment, the angles may be parallel and perpendicular to the air bearing surface. The difference in the inductance value can be used to determine a characteristic of the write head, such as the presence of a recording pole. In some embodiments, the inductance may be measured while applying a bias current to the write head while the write head is in an external magnetic field.

Abstract: A metrology device optically measures the electrical conductivity of a magnetic sample, such as a Tunneling Magnetoresistance (TMR) or Giant-Magneto Resistance (GMR) device, using Time Domain Thermo Reflectance (TDTR) to measure a cooling curve for the sample while a magnetic field is applied to the sample. The thermal conductivity of the sample may be determined using the cooling curve and the variation of the cooling curve with varying applied magnetic fields is measured. The electrical conductivity is determined for the sample in the magnetic field based on the thermal conductivity. If desired, single reflectance changes may be measured at a particular delay after heating, and the reflectance change at this delay may be used to determine the electrical conductivity. Of particular interest is the amount of change in electric conductivity for a given applied magnetic field because this yields a measure of the sensitivity of the sensor.

Abstract: A write head is tested by measuring the effect that magnetic fields have on the inductance of the write head. For example, a perpendicular write head may be placed in a magnetic field with a first angle, e.g., non-parallel and non-perpendicular, to the air bearing surface and the inductance is measured. After altering the angle of the magnetic field the inductance is again tested. In another embodiment, the angles may be parallel and perpendicular to the air bearing surface. The difference in the inductance value can be used to determine a characteristic of the write head, such as the presence of a recording pole. In some embodiments, the inductance may be measured while applying a bias current to the write head while the write head is in an external magnetic field.

Abstract: A crystal film with one or more nitrogen vacancy centers is placed in a magnetic field produced by a recording head and excitation illumination and a varying excitation field is applied. A confocal microscope or wide-field microscope optically detects a decrease in a spin dependent photoluminescence in response to the excitation illumination caused by electron spin resonance (ESR) of the at least one nitrogen vacancy center at varying excitation frequencies of the excitation field to measure Optically Detected Spin Resonance (ODMR). A characteristic of the recording head is determined using the ODMR.

Abstract: A polarization microscope optically detects the effect of the magnetic field from a sub-optical resolution magnetic structure on a magneto-optical transducer. The magneto-optical transducer includes a magnetic layer with a magnetization that is changed by the magnetic field produced by the magnetic structure. The saturation field of the magnetic layer is sufficiently lower than the magnetic field produced by the magnetic structure that the area of magnetization change in the magnetic layer is optically resolvable by the polarization microscope. A probe may be used to provide a current to the sample to produce the magnetic field. By analyzing the optically detected magnetization, one or more characteristics of the sample may be determined. A magnetic recording storage layer may be deposited over the magnetic layer, where a magnetic field produced by the sample is written to the magnetic recording storage layer to effect the magnetization of the magnetic layer.

Abstract: A polarization microscope optically detects the effect of the magnetic field from a sub-optical resolution magnetic structure on a magneto-optical transducer. The magneto-optical transducer includes a magnetic layer with a magnetization that is changed by the magnetic field produced by the magnetic structure. The saturation field of the magnetic layer is sufficiently lower than the magnetic field produced by the magnetic structure that the area of magnetization change in the magnetic layer is optically resolvable by the polarization microscope. A probe may be used to provide a current to the sample to produce the magnetic field. By analyzing the optically detected magnetization, one or more characteristics of the sample may be determined. A magnetic recording storage layer may be deposited over the magnetic layer, where a magnetic field produced by the sample is written to the magnetic recording storage layer to effect the magnetization of the magnetic layer.

Abstract: A testing device tests a magnetic head with a read head structure including a read head element while applying an external magnetic field to the magnetic head. The testing device receives signals from the read head element and processes the signals to generate a spectral power density for the signals. The spectral power density is characterized for at least one frequency range. The characterization of the spectral power density is used to determine a characteristic of noise from the read head structure. The signals from the read head may be received with different applied magnetic fields and/or before or while thermally exciting the magnetic head. Additionally, a histogram of the signals may be generated and used to determine a second characteristic of the noise.

Abstract: A metrology device optically measures the electrical conductivity of a magnetic sample, such as a Tunneling Magnetoresistance (TMR) or Giant-Magneto Resistance (GMR) device, using Time Domain Thermo Reflectance (TDTR) to measure a cooling curve for the sample while a magnetic field is applied to the sample. The thermal conductivity of the sample may be determined using the cooling curve and the variation of the cooling curve with varying applied magnetic fields is measured. The electrical conductivity is determined for the sample in the magnetic field based on the thermal conductivity. If desired, single reflectance changes may be measured at a particular delay after heating, and the reflectance change at this delay may be used to determine the electrical conductivity. Of particular interest is the amount of change in electric conductivity for a given applied magnetic field because this yields a measure of the sensitivity of the sensor.

Abstract: A tester for a testing a Hard Disk Drive (HDD) flex circuit prior to electrical installation of a Head Gimbal Assembly (HGA) includes a shorting block that makes electrical contact to the bondpads on the sample. The shorting block includes one or more electrical contacts that are electrically grounded and have a size and/or configuration to contact the bondpads as well as the surface of the sample around the bondpads to accommodate positioning tolerances of the sample under test, without need for optics, precise probes, or precision stages. The electrical contacts of the shorting block may be, e.g., a matrix of pogopins or a flexible electrically-conductive material. During testing, the bondpads are shorted together and to ground with the shorting block while it is determined whether Short failures are properly detected. While the shorting block is not engaged with the bondpads, it is determined whether open failures are properly detected.

Abstract: A property, such as a quality parameter, of a write pole in a write head is determined using an optical metrology device, where the write pole is smaller than the optical resolution limit of the metrology device. The metrology device produces polarized light that is reflected off the write pole while the write pole is magnetized either during or after excitation with a write current. The magnetization alters the polarization state of the light, which can be analyzed to transform the altered polarization state into intensity. The intensity of the light is detected over the point spread function of the optics in the metrology device and an intensity value is generated. The intensity value is used to determine the quality parameter of the write pole, e.g., by comparison to a threshold or reference intensity value, which may be generated empirically or theoretically.

Abstract: A magneto-optical transducer including a magnetic layer on a transparent, non-magnetic substrate is used to characterize the performance of a write head based on optically detected magnetization in the magnetic layer. The write head sample is held in contact with or near the magnetic layer, which is illuminated through the substrate with linearly polarized light. Magnetization in the write head produces a magnetization in the magnetic layer, which alters the polarization state in reflected light. The reflected light is analyzed and the intensity detected using an optical detector, such as one or more photo-detectors or a camera. The performance of the write head can then be characterized using the detected intensity.

Abstract: A magneto-optical transducer including a magnetic layer on a transparent, non-magnetic substrate is used to characterize the performance of a write head based on optically detected magnetization in the magnetic layer. The write head sample is held in contact with or near the magnetic layer, which is illuminated through the substrate with linearly polarized light. Magnetization in the write head produces a magnetization in the magnetic layer, which alters the polarization state in reflected light. The reflected light is analyzed and the intensity detected using an optical detector, such as one or more photo-detectors or a camera. The performance of the write head can then be characterized using the detected intensity.