  Highly symmetric magnetic environments have been suggested to stabilize the
magnetic information stored in magnetic adatoms on a surface. Utilized as
memory devices such systems are subjected to electron tunneling and external
magnetic fields. We analyze theoretically how such perturbations affect the
switching probability of a single quantum spin for two characteristic
symmetries encountered in recent experiments and suggest a third one that
exhibits robust protection against surface induced spin flips. Further we
illuminate how the switching of an adatom spin exhibits characteristic behavior
with respect to low energy excitations from which the symmetry of the system
can be inferred.

Mesoscale and Nanoscale Physics