Feasibility Tests on Pressure-Transmitting Media for Single-Crystal Magnetic Neutron Diffraction under High Pressure

The hydrostaticity of pressure-transmitting media, such as graphite powder, a mixture of Fluorinert, Fomblin oil, silicone oil, Daphne7373 oil and glycerin, was investigated by high-pressure neutron diffraction experiments on the mosaic spread of NaCl single crystals. The width of the rocking curve of the NaCl single crystal in the medium other than glycerin increases rapidly with increasing pressure below 2.5 GPa, indicating that the medium solidifies below 2.5 GPa. On the other hand, glycerin transmits nearly hydrostatic pressure at least up to 7 GPa. The diffraction profiles of the media were also measured to evaluate the background intensities. Daphne7373 oil and glycerin generate low and flat diffraction profiles particularly at approximately 25°, where the principal magnetic diffraction signals are often present. Thus, glycerin is the most suitable pressure medium for single-crystal magnetic neutron scattering experiments beyond 3 GPa.