Out-of-plane Enhanced Magnetic Anisotropy Energy in Ni₃Bz₃ molecule

Organometallic complexes formed by transition metals clusters and benzene molecules have already been synthesized, and in selected cases display magnetic properties controlled by external magnetic fields. We have studied Ni$_n$Bz$_n$ complexes made of nickel atoms surrounded by benzene molecules and here we focus specifically on the magnetic molecule Ni$_{3}$Bz$_{3}$. By means of calculations including relativistic spin-orbit terms, we show that this molecule reveals a large magnetic anisotropy energy of approximately 8 meV, found with the easy axis perpendicular to the metal atoms plane. Note that the matching bare Ni$_{3}$ cluster have similar magnetic anisotropy, however the easy axis is in-plane. Covering with benzene molecules is thus switching the easy axis from in-plane for Ni$_3$ to out-of-plane for Ni$_{3}$Bz$_{3}$. The large out-of-plane magnetic anisotropy of Ni$_{3}$Bz$_{3}$ suggests that this molecule could indeed be used as part in the design of molecular magnetic memories.