Fe magnetic transition under high pressure
Résumé
We have studied the high-pressure iron bcc to hcp phase transition by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Absorption Spectroscopy (XAS). The magnetic and structural transitions simultaneously observed are sharp. Both are of first order in agreement with theoretical prediction. The pressure domain of the transition observed (2.0 ± 0.1 GPa) is narrower than that usually cited in the literature (8 GPa). We have evidence that the magnetic transition slightly precedes the structural one, suggesting that the origin of the instability of the bcc phase in iron with increasing pressure is to be attributed to the effect of pressure on magnetism, rather than to phonon softening.