Pressure-induced lattice collapse was discovered in tetragonal (T) phase of single crystal ${\text{Fe}}_{1.05}\text{Te}$ at room temperature through x-ray and neutron-diffraction measurements. A remarkable compression along the $c$ axis $\left(\sim 5\%\right)$ was observed upon increasing pressure from the ambient condition to 4 GPa. Indexed results demonstrate that the crystallographic structure remains unchanged after the collapse, revealing that the collapse does not break symmetry of crystal structure. The Fe-spin state change was proposed to account for the lattice collapse. The equations of state for the T phase and pressure-induced collapsed T phase were determined from the diffraction measurements.

• Received 20 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.144519