Effective method to identify the vacancies in crystalline GeTe

X-ray diffraction and photoelectron spectroscopy of different Co-doped concentration GeTe have been made to identify the vacancies in rock-salt GeTe. The results show that Co occupies germanium vacancy and forms Co–Te bond, but the alloy retains a rock-salt structure when the concentration of doped Co is less than the vacancy ratio in crystalline GeTe. If we construct 8% germanium vacancy and relative distortion in rock-salt GeTe, the magnetism calculation based on spin-polarized density functional theory of Co-doped GeTe agrees well with superconducting quantum interference device magnetometer result. From experiment and calculation results, we can confirm the existence of vacancies in rock-salt GeTe and the ratio is 8%.