  When monolayers of two-dimensional (2D) materials are stacked into van der
Waals structures, interlayer electronic coupling can introduce entirely new
properties, as exemplified by recent discoveries of moir\'e bands that host
highly correlated electronic states and quantum dot-like interlayer exciton
lattices. Here we show the magnetic control of interlayer electronic coupling,
as manifested in tunable excitonic transitions, in an A-type antiferromagnetic
2D semiconductor CrSBr. Excitonic transitions in bilayer and above can be
drastically changed when the magnetic order is switched from layered
antiferromagnetic to the field-induced ferromagnetic state, an effect
attributed to the spin-allowed interlayer hybridization of electron and hole
orbitals in the latter, as revealed by GW-BSE calculations. Our work uncovers a
magnetic approach to engineer electronic and excitonic effects in layered
magnetic semiconductors.
