Ab initio cycloidal and chiral magnetoelectric responses in Cr_2O_3

摘要

We present a thorough density functional theory study of the magnetoelectric (ME) effect in Cr_2O_3. The spin-lattice ME tensor α was determined in the low-field and spin flop (SF) phases, using the method of dynamical magnetic charges, and found to be the sum of three distinct components. Two of them, a large relativistic "cycloidal" term and a small longitudinal term, are independent on the spin orientation. The third, only active in the SF phases, is also of relativistic origin and arises from magnetic-field-induced chirality, leading to a nontoroidal ME response.