What is VSM for magnetic measurement and its working principle?

Introduction:

VSM stands for Vibrating Sample Magnetometer, which is a widely used instrument for measuring the magnetic properties of materials. The VSM measures the magnetic moment of a sample as a function of an applied magnetic field.

Principle: 

The working principle of a VSM is based on Faraday's Law of Electromagnetic Induction. When a magnetic field is applied to a sample, it induces an electromotive force (EMF) in the sample, which produces a current in the sample. This current produces a magnetic field that opposes the applied field. The magnitude of the magnetic moment of the sample is directly proportional to the strength of the applied magnetic field and the induced EMF. The working principle of VSM is shown in Figure 1. 

Figure 1: Working principle of VSM system

In a VSM, the sample is mounted on a thin cantilever and placed between two magnetic poles. The cantilever is then vibrated at a high frequency, which allows the sample to rotate in the magnetic field. The magnetic moment of the sample is measured by detecting the changes in the amplitude of the cantilever's vibration, which is caused by the interaction between the magnetic field and the sample's magnetic moment.

As the magnetic field is increased, the magnetic moment of the sample aligns with the applied field, and the amplitude of the cantilever's vibration decreases. When the magnetic field is reversed, the magnetic moment of the sample also reverses, and the amplitude of the cantilever's vibration increases. By measuring the changes in the cantilever's vibration, the VSM can determine the magnetic moment of the sample as a function of the applied magnetic field. Figure 2 shows an example of magnetization behavior measurement by the VSM technique.

Figure 2: Hysteresis loop of magnetization dependent on history ferromagnetic magnetic field

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