  We propose a setup that is the spin analog of the charge-based quantum RC
circuit. We define and compute the spin capacitance and the spin resistance of
the circuit for both ferromagnetic (FM) and antiferromagnetic (AF) systems. We
find that the antiferromagnetic setup has universal properties, but the
ferromagnetic setup does not. We discuss how to use the proposed setup as a
quantum source of spin excitations, and put forward a possible experimental
realization using ultracold atoms in optical lattices.
