  We show that Co spins in Co/FeRh epitaxial bilayers grown on W(110) switch
reversibly between the two orthogonal in-plane directions as the FeRh layer
undergoes temperature driven antiferromagnetic-ferromagnetic (AFM-FM) phase
transition. Switching of Co magnetization is characterized by a hysteretic
behavior owing to a temperature hysteresis of the AFM-FM transition in FeRh.
The spin reorientation of Co is driven by the evolution interfacial exchange
coupling to FeRh system across the AFM-FM process. Our results provide a new
method of writing information purely by a local temperature change.
