Ferroelectricity in an Ising chain magnet

We report discovery of collinear-magnetism-driven ferroelectricity in the Ising chain magnet Ca(3)Co(2-x)Mn(x)O(6) (x approximate to 0.96). Neutron diffraction shows that Co(2+) and Mn(4+) ions alternating along the chains exhibit an up-up-down-down (up arrow up arrow down arrow down arrow) magnetic order. The ferroelectricity results from the inversion symmetry breaking in the up arrow up arrow down arrow down arrow spin chain with an alternating charge order. Unlike in spiral magnetoelectrics where antisymmetric exchange coupling is active, the symmetry breaking in Ca(3)(Co,Mn)(2)O(6) occurs through exchange striction associated with symmetric superexchange.