Alhassanat, A.; Gamer, C.; Rauguth, A.; Athanasopoulou, A. A.; Sutter, J.; Luo, C.; Ryll, H.; Radu, F.; Sapozhnik, A. A.; Mashoff, T.; Rentschler, E.; Elmers, H. J.: Element-specific magnetic properties of mixed 3d-4f metallacrowns. Physical Review B 98 (2018), p. 064428/1-8
10.1103/PhysRevB.98.064428
Abstract:
Single molecule magnets comprising rare earth metals are of high interest due to the unquenched orbital moments of the rare earth ions that result in a large energy barrier for magnetization reversal. We investigate the magnetic properties of polynuclear 3d−4f15-MC-5 metallacrowns using x-ray magnetic circular dichroism of powder samples at a temperature of 7 K in a magnetic field of 7 T. The sum rule analysis reveals element-specific spin and orbital moments. The magnetic moments of the 3d transition metal Ni(II) ions are coupled antiferromagnetically to each other and contribute only little to the total molecular moment. The spin and orbital moments of the rare earth ions are unexpectedly smaller than the ionic values resulting from Hund's rules. We explain the reduction of the orbital magnetic moment by a finite magnetic anisotropy. Considering an energy functional including magnetic anisotropy and Zeeman energy the powder average reveals a magnetic anisotropy of 28 meV (340 K) in the case of Dy(III) and 7 meV (85 K) in the case of Tb(III). The spin moments agree with the ionic value, too, when the expectation values of the dipole operator are considered.