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 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 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 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 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.

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 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 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 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 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 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.