Vibrating Sample Magnetometer
A Vibrating Sample Magnetometer (VSM, Eng. Magnetometer with vibrating sample ) is a magnetometer for determining the magnetic properties (e.g. the magnetic moment ) of a sample. The functional principle, in which the sample to be examined is set into periodic oscillations and the voltage induced in this way is measured, is based on a publication by Simon Foner from 1959.
Structure and functionality
The schematic structure of a Vibrating Sample Magnetometer can be seen in the adjacent figure. The sample, whose magnetic properties are to be measured, is attached to a sample holder and is positioned in a magnetic field that is as homogeneous as possible . The sample holder itself should have a low magnetization in order not to falsify the measurement result. The magnetic field is generated by an electromagnet . An actuator or piezo element sets the sample holder and the sample attached to it in periodic vibrations . Loudspeakers were originally used for this.
According to Faraday's law, the periodic oscillation of the magnetic sample leads to a change in the magnetic flux, which is measured with pick-up coils and a lock-in amplifier . A reference measurement of a sample with known properties can be used to calibrate the device. Several pairs of pick-up coils can also be used to determine direction-dependent or angle-dependent properties or to improve measurement accuracy.
The usability of the VSM is limited to relatively small samples because these should not protrude from the homogeneous area of the magnetic field. This often means that a degaussing correction has to be carried out, which compensates for the influence of the surface magnetic charges, in order to correctly determine the intrinsic properties of the material.
Similar magnetometers
Instead of vibrating the sample, it can also be set in rotation. If samples are generally sensitive to rotation, shaking or acceleration, the pick-up coils can be set in motion instead. In this case, one speaks of vibrating coil or rotating coil magnetometers.
Individual evidence
- ↑ Simon Foner: Versatile and Sensitive Vibrating-Sample Magnetometer . In: Rev. Sci. Instrum. . 30, No. 7, 1959, pp. 548-557. doi : 10.1063 / 1.1716679 .
- ^ Deposition and Processing . Academic Press ,, ISBN 978-0-12-512908-4 , pp. 407-408.
- ↑ David C. Jiles: Introduction to Magnetism and Magnetic Materials , 2nd Edition, CRC Press, 1998, ISBN 978-0-412-79860-3 , pp. 68-70.
- ↑ Pavel Ripka: Pavel Ripka (Ed.): Magnetic Sensors and Magnetometers . Artech House, 2001, ISBN 1-58053-057-5 , pp. 69-70.