  Search for single-molecule magnets (SMMs) with high blocking temperature (TB)
is urgent for practical applications in magnetic recording, molecular
spintronics and quantum computing. Based on the First-principles calculations,
magnetic anisotropy energies (MAE) of the transition metal-Phthalocyanine
(TM-Pc) molecules are investigated and the mechanism that determines the MAE of
TM-Pc molecules is established. In particular, colossal MAE > 100 meV can be
obtained by adding an Os atom on RuPc and OsPc, so these molecules may offer
ultrahigh thermal stability in devices.
