Nonrelativistic Multiferrocity in the Nonstoichiometric Spin- 1 2 spiral-chain Cuprate LiCu2 O2

Puzzling multiferroic behavior observed recently in spin-1/2 one-dimensional chain cuprate LiCu2 O2 with edge-shared arrangement of CuO4 plaquettes and incommensurate spiral spin ordering is consistently explained to be a result of the nonrelativistic exchange-induced electric polarization on the Cu2+ centers substituting for the positions native for the Cu1+ ions. These substituent centers are proven to be an effective probe of the spin incommensurability and magnetic field effects. © 2009 The American Physical Society.The authors thank A. Loidl, U. Rößler, K. Dörr, R. Kuzian, and H. Rosner for discussions. The DFG and RFBR grants (No. 06-02-17242, No. 07-02-96047, and No. 08-02-00633) are acknowledged for financial support