Variable pressure-temperature neutron diffraction of wüstite „Fe1−xO...: Absence of long-range magnetic order to 20 GPa

Neutron diffraction measurements have been performed on polycrystalline Fe1−xO swüstited up to 20.3 GPa using a large-volume moissanite anvil cell at room temperature to examine the existence of long-range magnetic ordering in the high-pressure rhombohedral phase of the material. This investigation is crucial for understanding the nature of high-pressure phase transitions in Fe1−xO. Low temperature ambient pressure neutron diffraction measurements on the same sample were also conducted at 190, 180, and 85 K to compare with the high-pressure results. Magnetic peaks are expected to be observed under pressure similar to those at 180 K at ambient pressure. However, no magnetic peaks were evident in the high-pressure diffraction patterns sto 20.3 GPa at 300 Kd. The absence of magnetic peaks indicates the absence of long-range magnetic order in Fe1−xO under these conditions. This result indicates the need to reconsider the interpretation of high-pressure Mössbauer studies and the mechanism of the high-pressure phase transitions in Fe1−xO. © 2005 American Institute of Physics. fDOI: 10.1063/1.1852075g