How Does a Vibrating Sample Magnetometer Calculate Magnetic Moment?

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SUMMARY

The discussion focuses on the calculation of magnetic moment using a Vibrating Sample Magnetometer (VSM). It highlights the relationship between induced voltage and magnetic moment, specifically through the equation emf = -dPhi/dt = - (dPhi/dz)(dz/dt). The confusion arises regarding the proportionality of (dPhi/dz) to the magnetic moment (m), which is clarified as an approximation based on small amplitude oscillations leading to a linear dependence of magnetic flux on the displacement (z).

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Physicists, materials scientists, and engineers involved in magnetic measurements and instrumentation, particularly those working with Vibrating Sample Magnetometers.

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TL;DR
How do you find the change in flux with respect to position
In descriptions of a VSM, the induced voltage in a coil is shown to be emf = -dPhi/dt = - (dPhi/dz)(dz/dt). From here, everyone seem to jump to a solution of emf = 2*Pi*A*f*m*sin(2*Pi*f*t).
That makes some sense: in this case, you can define z = A*cos(2*Pi*f*t) so (dz/dt) = 2*Pi*A*f*sin(2*Pi*f*t). I'm confused why (dPhi/dz) turns out to be equal to or proportional to m (the magnetic moment). Is it an approximation that assumes a small amplitude of oscillation and so a linear dependence of the magnetic flux on z? I am having trouble picturing this. Can someone help?
 
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What is a "VSM"? Is it a rotating coil in a magnetic field?
 
vanhees71 said:
What is a "VSM"? Is it a rotating coil in a magnetic field?
I guess it's his Vibrating Sample Magnetometer -- a quick search of Google Images turns up this:

1666717336498.png


https://en.wikipedia.org/wiki/Vibrating-sample_magnetometer
 

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