Ferroelectric Ferrimagnetic LiFe₂F₆: Charge Ordering Mediated Magnetoelectricit

The realization of magnetoelectric coupling between large polarization (P) and large magnetization (M) remains a big challenge despite tremendous efforts in the past decades. Here, we proposed a new bulk charge ordering (CO) multiferroic material, trirutile-type LiFe₂F₆, which can realize this desired magnetoelectric coupling [1]. The magnetic ground state was obtained to be A⁺-type antiferromagnetism, which is in agreement with previous neutron study [2]. Our DFT calculations indicate that LiFe₂F₆ is a charge-ordered material with Fe²⁺/Fe³⁺ configuration, which can lead to room-temperature ferroelectricity. More interestingly, the ferrimagnetic A⁻ state with a net magnetization of 0.5 μ_B/Fe can be stabilized by moderate compressive strain. Thus, LiFe₂F₆ can be a rare single phase multiferroic system with both P and M. Most importantly, since the charge ordering is the common ingredient for both P and M, the net M can be fully switched by flipping P, rendering an intrinsic strong magnetoelectric effect.

[1] L. -F. Lin, Q. R. Xu, Y. Zhang, J. -J. Zhang, Y. -P. Liang, and S. Dong, Phys. Rev. Mater. (under review).
[2] G. Shachar, J. Makovsky, and H. Shaked, Phys. Rev. B 6, 1968 (1972).