High Blocking Temperature of Magnetization and Giant Coercivity in the Azafullerene Tb-2@C79N with a Single-Electron Terbium-Terbium Bond ; Angewandte Chemie-International Edition

Abstract

The azafullerene Tb-2@C79N is found to be a single-molecule magnet with a high 100-s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy-axis single-ion magnetic anisotropy are strongly coupled by the unpaired spin of the single-electron Tb-Tb bond. Relaxation of magnetization in Tb-2@C79N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time tau(QTM)=16462 +/- 1230 s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757 +/- 4 K, corresponding to the excited states, in which one of the Tb spins is flipped. ; European Union's Horizon 2020 research and innovation programme, European Research Council [648295]; European Union's Horizon 2020 research and innovation programme, Marie Sklodowska-Curie action [748635]; Deutsche Forschungsgemeinschaft [PO 1602/4-1, 1602/5-1]; Luther & Alice Hamlett Scholarship ; We acknowledge funding from the European Union's Horizon 2020 research and innovation programme, European Research Council (grant agreement No 648295 to A.A.P.), and Marie Sklodowska-Curie action (grant agreement No. 748635 to S.M.A.), and the Deutsche Forschungsgemeinschaft (grants PO 1602/4-1 and 1602/5-1 to A.A.P.). K.K. acknowledges financial support from a Luther & Alice Hamlett Scholarship. Computational resources were provided by the Center for High Performance Computing at the TU Dresden. We appreciate the help from Dr. Anja U. B. Wolter and Sebastian Gass in magnetic measurements and technical support with computational resources in IFW Dresden by Ulrike Nitzsche.