  Recently it was shown that a molecule rotating in a quantum solvent can be
described in terms of the `angulon' quasiparticle [Phys. Rev. Lett. 118, 095301
(2017)]. Here we extend the angulon theory to the case of molecules possessing
an additional spin-1/2 degree of freedom and study the behavior of the system
in the presence of a static magnetic field. We show that exchange of angular
momentum between the molecule and the solvent can be altered by the field, even
though the solvent itself is non-magnetic. In particular, we demonstrate a
possibility to control resonant emission of phonons with a given angular
momentum using a magnetic field.
