Xianxin Wu, Yingxiang Cai, Qing Xie, Hongming Weng, Heng Fan, Jiangping Hu
Density-functional calculations are carried out to investigate incommensurate
magnetic structures and ferroelectric polarization in newly discovered
multiferrioc material $MnI_2$. We calculate magnetic exchange coupling
parameters and construct an effective magnetic model whose magnetic orders are
in good agreement with those measured experimentally. The measured direction of
polarization is also consistent with the result derived from the symmetry
analysis of the magnetically ordered state. In particular, we find that the
inter-plane magnetic exchange coupling is pivotal to the emergence of the
spiral magnetic structure that induces ferroelectricity. Our calculation
suggests that spin-orbit coupling on I ions is primarily responsible for the
appearance of the polarization.
View original:
http://arxiv.org/abs/1202.1884
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