Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 112: Electronic structure: Surface magnetism and spin phenomena II
O 112.5: Vortrag
Freitag, 16. März 2018, 11:30–11:45, MA 042
Spin excitations in a 4f–3d heterodimer on MgO — Aparajita Singha1, •Fabio Donati2,1,3, Fabian Donat Natterer1, Christian Wäckerlin1,4, Srdjan Stavric5, Zoran Popovic5, Zeljko Sljivancanin5, François Patthey1, and Harald Brune1 — 1Institute of Physics, Ecole Polytechnique Federale de Lausanne, Switzerland — 2Center for Quantum Nanoscience, Institute for Basic Science, Korea — 3Department of Physics, Ewha Womans University, Korea — 4Nanoscale Materials Science, Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland — 5Vinca Institute of Nuclear Sciences, Serbia
Many alloys of transition metals (TM) of the first row and rare earth (RE) elements posses large magnetic anisotropy. Atomic-scale structures made by these elements are intriguing model systems to explore unconventional magnetic phases where structural relaxations and interface effects can play a crucial role. Here we use scanning tunneling microscopy spin-excitation spectroscopy to unravel the magnetic level structure and exchange coupling in the smallest RE-TM cluster, namely HoCo dimers adsorbed on ultrathin layers of MgO on Ag(100). We observe two spin-excitations at ±8 and ±20 meV, the former being detectable with spin-polarized tips only. We model their magnetic field dependence with an effective spin Hamiltonian to identify the level splitting and the relative contribution of the two atoms to the spin excitation signal. Combining these results with density functional theory, we infer a ferromagnetic coupling between Ho and Co, which is opposite to what is known for late 4f–3d bulk compounds.