Magnetic Spin-Flop Transition of ?-FeOOH at 8 GPa

Mossbauer spectra of polycrystalline e-57FeOOH were measured up to 14.6 GPa at room temperature using the energy-domain synchrotron 57Fe Mossbauer source at BL11XU in SPring-8. Based on measurements with=without an external magnetic field, e-FeOOH appears to be antiferromagnetic at ambient pressure and temperature. On compression, the quadrupole shift 2e shifted from negative to positive at -8 GPa, which is consistent with a magnetic spin rotation. Previous XRD studies did not detect any transitions at this pressure; thus we infer the change in 2e to be the third pressure-induced transition without major structural change in addition to the hydrogen-bond symmetrization and electronic spin transition.

Automated summary

Mossbauer spectra of polycrystalline e-57FeOOH were measured up to 14.6 GPa at room temperature using the energy-domain synchrotron 57Fe Mossbauer source at BL11XU in SPring-8. Based on measurements with and without an external magnetic field, e-FeOOH exhibits antiferromagnetic behavior at ambient pressure and temperature. Compression-induced changes in the quadrupole shift 2e, observed at -8 GPa, suggest a magnetic spin rotation and indicate a third pressure-induced transition in addition to hydrogen-bond symmetrization and electronic spin transition, without significant structural changes as observed by previous XRD studies.