Harald Brune

september, 2022

22sep4:00 pm5:30 pmHarald BruneEcole Polytechnique Fédérale de Lausanne (EPFL), Switzerland4:00 pm - 5:30 pm KST

Event Details

Harald Brune

Academic Affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL)

Title: The role of External Shells in the Magnetic Stability of Single Rare-Earth Adatoms, new SAMs,  and Graphene Transfer under UHV


An important and often neglected fact in the magnetic stability of single rare-earth adatoms is the spin-polarization of their outer shells. It stems from charge transfer to the surface [1] and gives rise to an additional magnetic moment that is strongly coupled to the large and well-screened moment of the 4f electrons [2]. We present experimental evidence for Dy/g/Ir(111) that the total angular momentum resulting from these coupled 4f 5d6s moments is in fact the good quantum number that decides which states are stable and which mechanisms for reversal exist in a given crystal field [3]. Recent theoretical works have pointed out the importance of valence 5d6s shells for single atom and single ion molecular magnets [4], however, direct experimental evidence for the importance of these shells in the spin dynamics was so far lacking.

We discuss the most recent single atom magnets (SAMs) with focus on two cases where the easy axis is lying in-plane. The first is Dy on the TiO2(100)-terminated Dy/SrTiO3(100) surface [5] and the second Dy on MgO bridge sites [6]. In the first case, we present XMCD results and in the second preliminary SP-STM results studying the two-state switching as function of tunnel bias that we discuss in the context of published XMCD data [7]. In order to cap, respectively, seal samples that are sensitive to oxidation and other chemical reactions in ambient, we have transferred graphene under ultra-high vacuum. Since this is potentially relevant also for single atom magnets, we present our results that show clean graphene transfer under UHV onto Cu(100) and Ir(111) target samples using a wafer bonding approach.

[1] M. Pivetta et al. PRB 98, 115417 (2018).
[2] M. Pivetta et al. PRX 10, 031054 (2020).
[3] A. Curcella et al. to be published (2022).
[4] V. Dubrovin et al. Chem. Communic. 55, 13963 (2019) & Inorg. Chem. Front. 8, 2373 (2021).
[5] V. Bellini et al. ACS Nano 16, 11182 (2021).
[6] C. Soulard et al. in preparation (2022).
[7] F. Donati et al. Nano Lett. 21, 8266 (2021).
[8] D. Merk et al. submitted (2022).



(Thursday) 4:00 pm - 5:30 pm

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.