A vibrating-sample magnetometer (VSM) (also referred to as a Foner magnetometer) is a scientific instrument that measures magnetic properties based on Faraday’s Law of Induction. Simon Foner at MIT Lincoln Laboratory invented VSM in 1955 and reported it in 1959. Also it was mentioned by G.W. Van Oosterhout and by P.J Flanders in 1956. A sample is first placed in a constant magnetic field and if the sample is magnetic it will align its magnetization with the external field. The magnetic dipole moment of the sample creates a magnetic field that changes as a function of time as the sample is moved up and down. This is typically done through the use of a piezoelectric material. The alternating magnetic field induces an electric field in the pickup coils of the VSM. The current is proportional to the magnetization of the sample - the greater the induced current, the greater the magnetization. As a result, typically a hysteresis curve will be recorded and from there the magnetic properties of the sample can be deduced. The idea of vibrating sample came from D. O. Smith's vibrating-coil magnetometer. Typical VSM overview Parts of a typical VSM setup Actively cooled electromagnet/power supply Amplifier Control Chassis Meter Computer interface Sensor coils Vibration exciter with sample holder Hall probe (optional) Sample Operating Procedure: Mounting the sample in the sample holder Turning on the VSM system Run the computer software to initialize the system Calibrate the system Optimize the system for M Calibrate the Lock-In Amplifier Take measurements and record data Conditions for VSM to be effective Magnetic field must be strong enough to fully saturate the samples (or else inaccurate measurements will be taken) Magnetic field must be uniform across the sample space (otherwise the addition of field gradients will induce force that alter the vibration once again leading to inaccurate results Importance of pick-up coils These allow the VSM to maximize the induced signal, reduce the noise, give a wide saddle point, minimize the volume in between the sample and electromagnet to achieve a more uniform magnetic field at the sample space. The configuration of the coils can vary depending on the type of material being studied. Relation to Physics The VSM relies on Faraday's law of induction, with the detection of the emf given by , where N is the number of wire turns, A is the area, and the angle between the normal