Ferromagnetism in two-dimensional Fe3GeTe2; Tunability by hydrostatic pressure

We studied the effect of hydrostatic pressure on the magnetic properties of the highly anisotropic van der Waals ferromagnetic metal Fe3GeTe2 (FGT) with the field applied along the easy axis. The paramagnetic-to-ferromagnetic transition occurs at the Curie temperature T-c = 180K at ambient pressure, and T-c decreases monotonically by up to 15 K as the pressure increases up to 1.44 GPa, while the magnetization is suppressed by the pressure. By using high-pressure x-ray diffraction techniques, we found that the Fe-Fe bond lengths tend to decrease, and the Fe-Ge(Te)-Fe bond angles deviate away from 90 degrees under hydrostatic pressures, indicating the modification of the exchange interactions. First-principles calculations further confirm the pressure effects. These results suggest that the competition between direct-, super-, and double-exchange interactions plays a crucial role in the pronounced magnetic response under the hydrostatic pressure, i.e., the direct-exchange becomes stronger at a higher pressure and, hence, leading to increased antiferromagnetic components and thus deceased T-c. The highly tunable magnetic properties under hydrostatic pressure in this system provide robust routes for spin manipulation in low-dimensional material systems.

Automated summary

The study showed that the magnetic properties of Fe3GeTe2 are affected by hydrostatic pressure, leading to a decrease in Curie temperature and suppression of magnetization. High-pressure x-ray diffraction techniques revealed changes in Fe-Fe bond lengths and Fe-Ge(Te)-Fe bond angles under pressure. The competition between different exchange interactions plays a crucial role in the magnetic response under pressure.