Abstract: 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.

Abstract: A passive magnetic field shim arrangement including a plurality of shim pairs. For shimming a number of magnetic field harmonics, each shim pair may include a first shim and a second opposite and substantially equal shim, each shim pair being configured for shimming one of the magnetic field harmonics. Each shim pair may include a first shim of order N and a second opposite and substantially equal shim of order N, the first and second shims together defining a magnetic field shim correction of order N?1. Each shim may include one or more shim elements arranged on a non-magnetic tubular support, the tubular supports being dimensioned such that the tubular supports may be arranged concentrically in relation to each other.