  Two dimensional magnetic materials are at the forefront of the next
generation of spintronic devices. The possibility to interface them with other
van der Waals materials such as transition metal dichalcogenides has opened new
possibilities for the observation of new and exiting physical phenomena. Here,
we present a proof-of-concept valleytronic device based on
CrBr$_3$-encapsulated WSe$_2$ showing an unprecedented valley splitting of
$\sim 100$ meV under compressive strain of the WSe$_2$, able to be tuned by the
relative magnetization of the encapsulating layers. Multiscale transport
simulations performed on this device show a spin-valley current with a
polarization higher than 80$\%$ than is maintained in a range of $\sim$ 0.3 V
gate voltage in a field-effect transistor configuration. The impact of the
stacking configuration on the valley splitting is also evaluated.
