We study the nonreciprocal properties of the iron oxide α − Fe 2 O 3 (hematite) in the canted easy-plane antiferromagnetic phase, specifically in the GHz to THz frequency range. First, using the the microscopic spin Hamiltonian, we obtain the correct classical ground state where the canting is induced by the Dzyaloshinskii-Moriya interactions (DMI). The magnon spectrum is simulated using linear spin wave theory. We then compute the polarizability and the subgap optical conductivities using linear response. We find that the conductivity tensor contains frequency peaks at the zero momentum magnon gaps of order 0.1 meV which can be tuned by the DMI and on-site anisotropic spin interactions. Furthermore, we show that the canting-induced net magnetic moment m represents a measure for the effective time-reversal-symmetry breaking and nonreciprocity of the system: A finite m results in a nonzero Hall conductivity. Finally, we discuss the prospective application of hematite in nonreciprocal circulator design, by computing the nonreciprocal circulator transmission amplitude using the conductivities as input.
