Multiferroic Properties of Polar Metallocenes

Polar metallocenes have been designed computationally with interesting atomic, electronic and magnetic structures [1]. Their properties have been studied using density functional theory with the non-local van der Waals DF2 functional. This is a challenge for current density functional codes, as accurate DF2 and magnetism with spin-orbit are required along with application of electric and magnetic fields to probe multiferroic properties. Most computations here were performed with quantum espresso, VASP, and CP2K. I will concentrate here on 5-fluoroferrocene C10H5F5Fe, predicted to be a polar antiferromagnetic and 1-azamangecene C9NH9Mn a polar ferromagnet. First-principles MD shows stability of both polar metallocenes to at least 1400K—i.e. Tc and melting are perhaps above 1400K. The Mn in 1-azamangocene is particularly interesting: computations show it to be low spin with a negative Born effective charge and static Hirshfeld charge. Experimental studies of these systems would be very exciting.

1          Zhang, H., Yavorsky, B. Y. & Cohen, R. E. Polar Metallocenes. molecules 24, doi:10.3390/molecules24030486 (2019).