Vibrating Sample Magnetometers (VSM)

Vibrating Sample Magnetometers, as the name implies, vibrate the sample as part of the measurement process.  This provides the Fluxmeter element of the system with the dynamic component it requires to make the measurement.  The applied field is changed so at each measurement point the field is static and hence no eddy currents to cause problems.

VSM’s typically use a lock-in amplifier as part of the magnetism detection process that provides the capability of generating highly sensitive measurements and subsequently is very useful for extremely small samples i.e. thin-films etc.

The applied field is often generated using iron-pole pieces and a field solenoid that limits the field to approximately 2.4 Tesla.   While this is fine for some materials it presents a serious limitation on the VSM.

The alternative is to use super conducting coils.  This is where a field generation coil is surrounded by liquid nitrogen, or even liquid helium to reduce resistance and provide cooling.  This allows high fields to be generated but at the expense of a high initial cost and high running costs with very long measurement times (see table above)

VSM’s use an open circuit form of magnetic measurement and must account for self-demagnetisation effects.

They are excellent for use with very small samples but as the magnets get larger the mass of the sample proves problematic, as this must be vibrated.