Magnetically Induced Polarization in Centrosymmetric Bonds

We reveal the microscopic origin of electric polarization induced by noncollinear magnetic order. We show that in Mott insulators, such is given by all possible combinations of position operators and transfer integrals in the bonds, where and are spin-independent contributions in the basis of Kramers doublet states, while and stem solely from the spin-orbit interaction. Among them, the combination , which couples to the spin current, remains finite in the centrosymmetric bonds, thus yielding finite in the case of noncollinear arrangement of spins. The form of the magnetoelectric coupling, which is controlled by , appears to be rich and is not limited to the phenomenological law with being the bond vector connecting the spins and . Using density-functional theory, we illustrate how the proposed mechanism works in the spiral magnets , , CuO, and , providing a consistent explanation for the available experimental data. © 2021 American Physical Society.We are grateful to the anonymous referee of Ref. for drawing our attention to the intersite matrix elements of . I. S. was supported by program AAAA-A18-118020190095-4 (Quantum)