Measuring Magnetization by Force:

If the potential energy of a magnetic moment in a given magnetic field is U = - m.B, then the force is derivative of energy with respect to distance:

If we place the sample in a region of constant dB/dz and non-zero overall B, it will experience a force. In addition, if the gradient is in vertical direction, this will serve to change the weight of the sample.

By measuring the apparent weight of the sample with the field gradient on and off, one can measure force on the sample (as shown in Figure 28.01) resulting in from its net magnetization. This technique is known as the Faraday balance method, and works for smaller samples.

Figure 28.01: Schematic drawing of Faraday's method for measuring magnetization by force.