Method of and apparatus for torque magnetometry

A method of and apparatus for torque magnetometry is disclosed. A specimen (2), the magnetic moment of which it is desired to determine, is disposed on a support means. A temporally varying, for example sinusoidal, magnetic field Bext is generated in the region of the specimen so that interaction between the magnetic moment M of the specimen and the magnetic field causes a torque to be exerted on the specimen. Consequently the specimen and/or the support are deflected, typically a vibratory motion is set up. Means are provided to measure the motion of the specimen and/or support due to the torque. When the magnitude and direction of the magnetic field are known, the magnetic moment of the specimen can be determined from the results of the motion measurement. The frequency of the magnetic field can be adjusted so that the specimen and/or the support resonate. The support is typically a single silicon crystal having two orthogonal modes of vibration which have different resonant frequencies. This can facilitate the independent determination of the three orthogonal components of the magnetic moment of the specimen.