# inverse_kittel¶

Stoner.analysis.fitting.models.magnetism.inverse_kittel(f, g, M_s, H_k)[source]

Rewritten Kittel equation for finding ferromagnetic resonsance in field with frequency.

Parameters
• f (array) – Resonance Frequency in Hz

• g (float) – g factor for the gyromagnetic radius

• M_s (float) – Magnetisation of sample in A/m

• H_k (float) – Anisotropy field term (including demagnetising factors) in A/m

Returns

Reesonance peak frequencies in Hz

Notes

In practice one often measures FMR by sweepign field for constant frequency and then locates the peak in H by fitting a suitable Lorentzian type peak. In this case, one returns a $$H_{res}\pm \Delta H_{res}$$ In order to make use of this data with Stoner.Analysis.AnalysisMixin.lmfit() or Stoner.Analysis.AnalysisMixin.curve_fit() it makes more sense to fit the Kittel Equation written in terms of H than frequency.

$$H_{res}=- H_{k} - \frac{M_{s}}{2} + \frac{1}{2 \gamma \mu_{0}} \sqrt{M_{s}^{2} \gamma^{2} \mu_{0}^{2} + 16 \pi^{2} f^{2}}$$