An additional area of research we are involved with concerns multi-ferroic fluorides. For our purposes, multi-ferroic materials exhibit ferroelectricity, i.e. reversible polarization, and some sort of magnetic ordering (ferro-, anti-ferro, ferrimagnetism). The interest with multi-ferroic materials stems from their applications in information storage. Suggestions have been made that on a single multi-ferroic bit, information could be independently encoded by both polarization and magnetization. We are investigating magnetic ordering in materials that undergo a ‘non-classic’ ferroelectric mechanism, e.g., BaNiF₄ (see Figure). As seen in the Figure, the green octahedra and yellow spheres represent the structure of the ‘up’ polarization of BaNiF₄, whereas the gray octahedral and spheres represent the structure of the ‘down’ polarization. The structural re-orientation through the NiF₆ octahedral rotations and Ba²⁺ displacements result in the polarization reversal, switching between ‘up’ and ‘down’, i.e. the ferroelectric behavior. We are investigating a host of mixed-metal fluorides that could undergo this non-classic ferroelectric mechanism and exhibit magnetic ordering.

Recent Publications

• Kim, S.W., Zhang, R., Halasyamani, P.S., and Hayward, M.A. K₄Fe₃F₁₂: An Fe²⁺ / Fe³⁺ Charge-Ordered Ferrimagnetic Fluoride with a Cation-Deficient Layered Perovskite Structure, Inorg. Chem., In Press, 2015.
• Thao, T.T. and Halasyamani, P.S., Synthesis and Characterization of ASnF₃ (A = Na⁺, K⁺, Cs⁺), J. Solid State Chem., 210, 213-218, 2014.
• Kim, S. W., Kim, S.-H., Halasyamani, P. S., Green, M. A., Bhatti, K. P., Leighton, C., Das, H., and Fennie, C., RbFe²⁺Fe³⁺F₆: Synthesis, Structure, and Characterization of New Charge-Ordered Pyrochlore-Related Magnetically Frustrated Mixed-Metal Fluoride, Chem. Sci., 3, 741-751, 2012.
• Liang, K.-C., Zhang, W., Lorenz, B., Sun, Y.Y., Halasyamani, P.S., and Chu, C.W., Weak ferromagnetism and internal magnetoelectric effect in multiferroic LiFeP₂O₇, Phys. Rev. B., 86, 094414-1-094414-7, 2012.
• Kim, S.-W., Chang, H.Y., and Halasyamani, P.S., Selective Pure-Phase Synthesis of the Multi-Ferroic BaMF₄ (M = Mg, Mn, Co, Ni, and Zn) Family, J. Am. Chem. Soc., 132, 17684-17685, 2010.