Improper magnetic ferroelectricity of nearly pure electronic nature in cycloidal spiral CaMn${}_7$O${}_{12}$

Jin Soo Lim, Diomedes Saldana-Greco, Andrew M. Rappe

The noncollinear cycloidal magnetic order breaks the inversion symmetry in CaMn${}_7$O${}_{12}$, generating one of the largest spin-orbit driven ferroelectric polarizations measured…