  The research on van der Waals (vdW) layered ferromagnets have promoted the
development of nanoscale spintronics and applications. However, low-temperature
ferromagnetic properties of these materials greatly hinder their applications.
Here, we report pressure-enhanced ferromagnetic behaviours in layered CrSiTe3
flakes revealed by high-pressure magnetic circular dichroism (MCD) measurement.
At ambient pressure, CrSiTe3 undergoes a paramagnetic-to-ferromagnetic phase
transition at 32.8 K, with a negligible hysteresis loop, indicating a soft
ferromagnetic behaviour. Under 4.6 GPa pressure, the soft ferromagnet changes
into hard one, signalled by a rectangular hysteretic loop with remnant
magnetization at zero field. Interestingly, with further increasing pressure,
the coercive field (H_c) dramatically increases from 0.02 T at 4.6 GPa to 0.17
T at 7.8 GPa, and the Curie temperature (T_c^h: the temperature for closing the
hysteresis loop) also increases from ~36 K at 4.6 GPa to ~138 K at 7.8 GPa. The
influences of pressure on exchange interactions are further investigated by
density functional theory calculations, which reveal that the in-plane
nearest-neighbor exchange interaction and magneto-crystalline anisotropy
increase simultaneously as pressure increases, leading to increased H_c and
T_c^h in experiments. The effective interaction between magnetic couplings and
external pressure offers new opportunities for both searching room-temperature
layered ferromagnets and designing pressure-sensitive magnetic functional
devices.
