  The ability to control magnetic properties of materials is crucial for
fundamental research and underpins many information technologies. In this
context, two-dimensional materials are a particularly exciting platform due to
their high degree of tunability and ease of implementation into nanoscale
devices. Here we report two approaches for manipulating the A-type
antiferromagnetic properties of the layered semiconductor CrSBr through
hydrostatic pressure and ligand substitution. Hydrostatic pressure compresses
the unit cell, increasing the interlayer exchange energy while lowering the
N\'eel temperature. Ligand substitution, realized synthetically through Cl
alloying, anisotropically compresses the unit cell and suppresses the
Cr-halogen covalency, reducing the magnetocrystalline anisotropy energy and
decreasing the N\'eel temperature. A detailed structural analysis combined with
first-principles calculations reveal that alterations in the magnetic
properties are intricately related to changes in direct Cr-Cr exchange
interactions and the Cr-anion superexchange pathways. Further, we demonstrate
that Cl alloying enables chemical tuning of the interlayer coupling from
antiferromagnetic to ferromagnetic, which is unique amongst known
two-dimensional magnets. The magnetic tunability, combined with a high ordering
temperature, chemical stability, and functional semiconducting properties, make
CrSBr an ideal candidate for pre- and post-synthetic design of magnetism in
two-dimensional materials.
