Abstract

The 57 Fe nuclear forward scattering (NFS) of synchrotron radiation and the use of diamond anvils with helium as pressure medium allowed study of the electronic state of Fe (super 2+) in the chain silicate hedenbergite CaFeSi 2 O 6 at pressures up to 68 GPa. Characteristics of NFS time spectra were compared with those of conventional Mossbauer spectra. NFS time spectra of 57 Fe in hedenbergite revealed a reversible phase transition between 53 and 68 GPa at room temperature, which is probably a transition from the paramagnetic phase at low pressures to a magnetic phase at high pressures. If this interpretation is correct, the Neel temperature T N of hedenbergite depends critically on pressure (T N = 45 K at 1 atm).

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