Out-of-plane magnetic anisotropy energy in the NiBz 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 NinBzn complexes made of nickel atoms surrounded by benzene molecules and here we focus specifically on the magnetic molecule Ni3Bz3. 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 atom plane. Note that the matching bare Ni3 cluster has a similar magnetic anisotropy, however the easy axis is in-plane. Covering with benzene molecules thus switches the easy axis from in-plane for Ni3 to out-of-plane for Ni3Bz3. The large out-of-plane magnetic anisotropy of Ni3Bz3 suggests that this molecule could indeed be used as a part in the design of molecular magnetic memories.