(Invited) The Role of Gd in the Dy2GdN@C80 single Molecule Magnet

Abstract

Endohedral fullerenes are perfect nanolaboratories for the study of 4f electron magnetism. The substitution of a diamagnetic scandium atom in Dy2ScN@C80 with magnetically isotropic gadolinium decreases the stability of a given magnetization that is imposed by the Dy2 unit and demonstrates Gd to accelerate the reaching of thermal equilibrium. X-ray magnetic circular dichroism at the M4,5 edges of Gd and Dy shows that Gd also affects the magnetic ground state. The Gd magnetic moment follows the sum of the external and the dipolar magnetic field of the two Dy ions and compared to Dy2ScN@C80 a lower exchange barrier is found between the ferromagnetic and the antiferromagnetic Dy configuration. The Arrhenius equilibration barrier as obtained from superconducting quantum interference device magnetometry is more than one order of magnitude larger, though a much smaller prefactor imposes the faster equilibration in Dy2GdN@C80. This sheds light on the importance of angular momentum balance and symmetry in magnetic relaxation [1].[1] Gadolinium as a single atom catalyst in a single molecule magnet, Aram Kostanyan, Christin Schlesier, Rasmus Westerstrom, Jan Dreiser, Fabian Fritz, Bernd Buchner, Alexey A. Popov, Cinthia Piamonteze, Thomas Greber, arXiv:2009.12259 September (2020).The figure shows the Dy2GdN@C80 molecule where the two Dy 4f9 and the Gd 4f7 orbitals of the paramagnetic entities are shown in red. Note the orientation of the Jz=15/2 Dy 4f9 orbitals towards the N3- ligand. Picture by Ari P. Seitsonen. Figure 1