  The discovery of long-range magnetic ordering in atomically thin materials
catapulted the van der Waals (vdW) family of compounds into an unprecedented
popularity. In particular, with a current push in space exploration, it is
beneficial to study how the properties of such materials evolve under proton
irradiation. Owing to their robust intra-layer stability and sensitivity to
external perturbations, these materials provide excellent opportunities for
studying proton irradiation as a non-destructive tool for controlling their
magnetic properties. Specifically, the exfoliable Cr2Si2Te6 (CST) is a
ferromagnetic semiconductor with the Curie temperature (TC) of ~32 K. Here, we
have investigated the magnetic properties of CST upon proton irradiation as a
function of fluence (1 x 1015, 5 x 1015, 1 x 1016, 5 x 1016, and 1 x 1018
H+/cm2) by employing variable-temperature, variable-field magnetization
measurements coupled with electron paramagnetic resonance (EPR) spectroscopy
and detail how the magnetization, magnetic anisotropy and EPR spectral
parameters vary as a function of proton fluence across the magnetic phase
transition. While the TC remains constant as a function of proton fluence, we
observed that the saturation magnetization and magnetic anisotropy diverge at
the proton fluence of 5 x 1016 H+/cm2, which is prominent in the ferromagnetic
phase, in particular. This work demonstrates that proton irradiation is a
feasible method for modifying the magnetic properties and local magnetic
interactions of vdWs crystals, which represents a significant step forward in
the design of future spintronic and magneto-electronic applications.
