Single-cristal X-ray diffraction study of the Pressure - Temperature phase diagram of the structure of nickel ferrite

The Nickel ferrite, which is known to belong to the inverse spinel family (cubic F-3m space group) exhibits ferromagnetism below 870 K. Recently it has been reported that this system also exhibits ferroelectricity below 98K, concomitant to a structural distortion from Fd\bar{3}m to the P4122 space group. While our attempt to confirm this structural distortion at low temperature failed so far, our recent X-ray absorption spectroscopy measurements under pressure and at room temperature surprisingly revealed the presence of a wide transition occurring between 30 and 55 GPa, which nature remain puzzling. This proposal aims at characterizing, in detail, the crystallographic structure of the spinel NiFe2O4 at low and room temperature, ambient pressure and above 55 GPa to have a complete overview of the (Pressure - Temperature) structural phase diagram of this system.