  The concept of swapping the two most important spin interactions -- exchange
and spin-orbit coupling -- is proposed based on two-dimensional multilayer van
der Waals heterostructures. Specifically, we show by performing realistic ab
initio simulations, that a single device consisting of a bilayer graphene
sandwiched by a 2D ferromagnet Cr$_2$Ge$_2$Te$_6$ (CGT) and a monolayer WS$_2$,
is able not only to generate, but also to swap the two interactions. The highly
efficient swapping is enabled by the interplay of gate-dependent layer
polarization in bilayer graphene and short-range spin-orbit and exchange
proximity effects affecting only the layers in contact with the sandwiching
materials. We call these structures ex-so-tic, for supplying either exchange
(ex) or spin-orbit (so) coupling in a single device, by gating. Such
bifunctional devices demonstrate the potential of van der Waals spintronics
engineering using 2D crystal multilayers.
