In ferromagnetic resonance experiments, the ferromagnetic sample is used to saturate intially and then the resonance experiments is carried out. What is the purpose of saturation?
Hmm. (1) To observe the resonance, the sample must be magnetized. Otherwise you will not get a net signal. (2) The external magnetic field is usually tuned across a range of values which allows the resonance to actually take place at the frequency of the rf source driving the magnetization rotation (or several frequencies in case you can afford multiple sources). The frequency being usually fixed, the field is the control variable of the experiment (besides temperature, pressure or other parameters). Samples with different magnetizations will display the resonance at different values of the external field.
If the sample wasn't saturated initially, it might not be in a "single domain state". Saturating in a high field ensures that any domain walls (especially the 360 degree walls pinned at defects) are driven out of the sample.
In the case of perturbation analysis, people used to perturb the fields around the saturated state. what is the reason for this? especially using the soliton theory.
Dear Sir
Find the attachment for soliton in ferromagnet subject to electromagnetic wave propagation.
The perturbation expansion is expanded about the saturation magnetization. The saturation magnetization is obtained by immersing the ferromagnet in a strong external magnetic field.
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