Coexisting ferromagnetic component and negative magnetoresistance at low temperature in single crystals of the VdW material GaGeTe

We report magnetoresistance and magnetization studies of single-crystal GaGeTe, which has been proposed as a Van der Waals material. Semi-metallic character is observed in the temperature (T) variation of resistivity (ρ), following ρ(T) ​∝ ​T2 ​at low temperature with a slope compatible with the usual spin-fluctuating system. Magnetoresistance (MR) at 2 ​K is negative and strongly dependent on the direction of the magnetic field (H) with respect to the crystallographic c-axis. MR changes sign with increasing temperature above ∼ 100 ​K, when H is applied along the c-axis. Hall measurements indicate the p-type conductivity with a considerable hole concentration of ∼ 8.7 ​× ​1019 ​cm−3. Angle-resolved photoemission spectroscopy reproduces the reported results and confirms a peculiar dispersion shape of the hole-like band at the bulk high-symmetry T point near the Fermi energy indicating band inversion. Magnetic hysteresis measurement at 2 ​K shows diamagnetic behaviour at high-H, whereas a ferromagnetic (FM)-like magnetic hysteresis loop is observed at low-H in between ​± ​4 ​kOe. The FM component disappears close to 3 ​K. Signature of spin-fluctuation in ρ(T), negative MR, and low-T FM component without 3d or 4f impurities in GaGeTe is attractive for the fundamental interest.