  van der Waals (vdW) magnets, an emerging family of two-dimensional (2D)
materials, have received tremendous attention due to their rich fundamental
physics and significant potential for cutting-edge technological applications.
In contrast to the conventional bulk counterparts, vdW magnets exhibit
significant tunability of local material properties, such as stacking
engineered interlayer coupling and layer-number dependent magnetic and
electronic interactions, which promise to deliver previously unavailable merits
to develop multifunctional microelectronic devices. As a further ingredient of
this emerging topic, here we report nanoscale quantum sensing and imaging of
atomically thin vdW magnet chromium thiophosphate CrPS4, revealing its
characteristic layer-dependent 2D static magnetism and dynamic spin
fluctuations. We also show a large tunneling magnetoresistance in CrPS4-based
spin filter vdW heterostructures. The excellent material stability, robust
strategy against environmental degradation, in combination with tailored
magnetic properties highlight the potential of CrPS4 in developing
state-of-the-art 2D spintronic devices for next-generation information
technologies.
