X-ray absorption spectroscopy and x-ray magnetic circular dichroism simultaneous measurements under high pressure:: the iron bcc-hcp transition case

XAS (x-ray absorption spectroscopy) and XMCD (x-ray magnetic circular dichroism) studies performed simultaneously give the structural and the magnetic properties of the same compound in rigorously the same thermodynamic conditions. The high pressure iron bcc to hcp phase transition has been studied with these combined techniques. The magnetic and structural transitions are sharp. Both are of first order and they occur in the same pressure domain, as theoretically predicted. The pressure domain of the structural transition is found at around 2.4 +/- 0.2 GPa, narrower than usually described in the literature. No room temperature ferromagnetic order has been found in the iron hcp phase close to the transition pressure. The magnetic transition occurs in a narrower domain and slightly precedes the structural one.