Ferromagnetism in two-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mi>Ge</mml:mi><mml:msub><mml:mi>Te</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>; Tunability by hydrostatic pressure
Shilei Ding, Zhongyu Liang, Jie Yang, Chao Yun, Peijie Zhang, Zefang Li, Mingzhu Xue, Zhou Liu, Guang Tian, Fuyang Liu, Wenhong Wang, Wenyun Yang, Jinbo Yang
Abstract
We studied the effect of hydrostatic pressure on the magnetic properties of the highly anisotropic van der Waals ferromagnetic metal ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$ (FGT) with the field applied along the easy axis. The paramagnetic-to-ferromagnetic transition occurs at the Curie temperature ${T}_{c}=180\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ 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 ${90}^{\ensuremath{\circ}}$ 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.