According to one embodiment, a defect registration method includes measuring, performing first extracting, and registering. The measuring is measuring, on a unit-area basis, performance of a storage area of a magnetic disk including a plurality of unit areas. The storage area includes a redundant area of a set capacity. The first extracting includes second extracting one or more unit areas in order of increasing the performance. The registering is registering the extracted unit areas of the set capacity as defect locations.

A magnetic property measuring system includes coil structures configured to apply a magnetic field to a sample, a light source configured to irradiate incident light to the sample, and a detector configured to detect polarization of light reflected from the sample. The magnetic field is perpendicular to a surface of the sample. Each coil structure includes a pole piece and a coil surrounding an outer circumferential surface of the pole piece. A wavelength of the incident light is equal to or less than about 580 nm.

A magnetic testing apparatus includes a magnet assembly with a sample path extending through the magnet assembly. The magnetic field produced by the magnet assembly defines a known, varying magnetic field profile along the sample path. A sample is moved along sample path such that the sample portion is subjected to a predetermined magnetic field ramp or magnetic field profile during a measurement period. A measurement arrangement is also provided to measure one or more properties of the sample during the measurement period, in order to test sample properties at a plurality of different magnetic fields. The apparatus may be particularly suited to magneto-optical measurements, including Magneto-Optical Kerr Effect measurements. The apparatus may be used for testing of hard disk platters.

A method and device for determining values of a magnetic field component of a magnetic vector field. A method for determining values of a magnetic field component of a magnetic vector field, comprising: determining first distribution data comprising values of the magnetic field component, for a first predetermined area defined along a predetermined surface; determining second distribution data comprising second values of the component of the magnetic field for a second predetermined area defined along a second predetermined surface, wherein the first and the second predetermined surfaces are parallel;
wherein determining second distribution data comprises manipulation of the first distribution data based on making use of intrinsic physical properties of the magnetic field; and associated device.

According to one embodiment, a defect registration method includes measuring, performing first extracting, and registering. The measuring is measuring, on a unit-area basis, performance of a storage area of a magnetic disk including a plurality of unit areas. The storage area includes a redundant area of a set capacity. The first extracting includes second extracting one or more unit areas in order of increasing the performance. The registering is registering the extracted unit areas of the set capacity as defect locations.

A method includes receiving a first set of testing data associated with a first group of electronic devices. The first set of testing data is generated during a tuning test applying a first range of testing parameters. The method further includes receiving a second set of testing data associated with the first group of electronic devices. Further, the method includes determining, based on the first set of testing data and the second set of testing data, a second range of testing parameters that is less than the first range of testing parameters. The method includes testing a second group of electronic devices using a tuning test applying the second range of testing parameters.

A method of testing dynamic performances for a slider body of a thermally-assisted magnetic head includes: providing a slider body which is disconnected with a light source unit; removably mounting the slider body to a test head suspension assembly; keeping to provide a flat top beam to the slider body, the flat top beam being aligned with the optical waveguide, and a projection of an incident end of the optical waveguide being located within a light spot of the flat top beam; and testing the dynamic performance of the slider body. It can save the material cost and labor cost, and eliminate a precise optical alignment between an input light and an optical waveguide in the slider body to improve testing efficiency.

Aspects of this disclosure relate to one or more particles that move within a container in response to a magnetic field. A measurement circuit is configured to output an indication of the magnetic field based on position of the one or more particles.

A multilayer exchange spring recording media consists of a magnetically hard magnetic storage layer strongly exchange coupled to a softer nucleation host. The strong exchange coupling can be through a coupling layer or direct. The hard magnetic storage layer has a strong perpendicular anisotropy. The nucleation host consists of one or more ferromagnetic coupled layers. For a multilayer nucleation host the anisotropy increases from layer to layer. The anisotropy in the softest layer of the nucleation host can be two times smaller than that of the hard magnetic storage layer. The lateral exchange between the grains is small. The nucleation host decreases the coercive field significantly while keeping the energy barrier of the hard layer almost unchanged. The coercive field of the total structure depends on one over number of layers in the nucleation host. The invention proposes a recording media that overcomes the writeability problem of perpendicular recording media.

Described are probe assemblies that include multiple layers, including at least one layer of probe bodies; suspension assemblies and components thereof, e.g., head gimbal assemblies, that include a probe assembly as described; and methods of using the probe assemblies and suspension assemblies.