Puzzling multiferroic behavior observed recently in spin-1/2 one-dimensional chain cuprate ${\text{LiCu}}_2{\text{O}}_2$ with edge-shared arrangement of ${\text{CuO}}_4$ plaquettes and incommensurate spiral spin ordering is consistently explained to be a result of the nonrelativistic exchange-induced electric polarization on the ${\text{Cu}}^{2+}$ centers substituting for the positions native for the ${\text{Cu}}^{1+}$ ions. These substituent centers are proven to be an effective probe of the spin incommensurability and magnetic field effects.

• Received 2 October 2008

DOI:https://doi.org/10.1103/PhysRevB.79.104112