Explain how you can deduce from these spectra the sign of the hyperfine field of Sr in iron, and put your thoughts in the forum underneath (in case you would not get to the full explanation, then try to formulate where you get stuck).
So what changes on the spectra due to increasing applied B?
1. The resonance frequency decreases
2. The peak depth (so the change in anisotropy at resonance)
3. The peak width
Having a negative B_hf would mean it opposes the applied field i think (i’m not sure about this). A lower resonance frequency leads to a lower energy splitting due to zeeman splitting. This means that with increasing B_applied your energy splitting drops, so I’d say you need a negative contribution from your B_hf to counter this. (so the sign is negative)