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Theme 3 colloquium with two speakers and Christmas afterparty! (Lecture)

Tuesday 18 December 2018Add to my calendar
from 16:00
HG00.303, Holiday afterparty on 1st floor North side
dr. Fabian Natterer (Physik-Institut, Univ. of Zurich, Switzerland)
Characterizing Single Atom Magnets using Scanning Tunneling Microscopy enabled Electron Spin Resonance
Preceding lecture
Umut Kamber, MSc (Scanning Probe Microscopy): "Magnetic order in Nd(0001): a new type of spin glass?"

Abstract Fabian Natterer
Fabian NattererThe smallest classical storage unit is a single atom bit. Its recent discovery in form of magnetically bistable holmium single atom magnets on MgO exemplified how miniaturization could be realized down to fundamental limits. Here we discuss the experiments leading to the observation of magnetic remanence, the reading and writing of single atom magnets, and the investigation of their thermal and magnetic stability. Using STM enabled electron spin resonance, we find a magnetic moment of (10.1±0.1) Bohr magnetons and we prove the magnetic origin of the tunneling bias voltage dependent 2-state switching observed with spin-polarized electrons. We briefly review the used measurement concept of ESR-STM and illustrate new avenues for this technique.

Abstract Umut Kamber:
Umut KamberLanthanide metals can exhibit complex magnetic structures, e.g. helical/conical spin spirals or linear spin waves [1]. However, most investigations of their magnetic structure so far are based on magnetic neutron or X-ray diffraction experiments, lacking spatial resolution. Therefore, the variations in magnetic properties of lanthanides at the atomic length scale are poorly understood. Neodymium (Nd) shows the most complicated magnetic phase diagram among the lanthanides. It exhibits several magnetic phase transitions below its Néel temperature of 19.9 K, resulting in multi-q magnetic order according to the interpretation of the diffraction experiments [2,3]. The surface electronic structure of Nd(0001) has also been studied using STS [4,5]. Here, we present ultra-low temperature SP-STM measurements of (0001)-terminated bulk-like Nd films grown on W(110). We observe multi-q behavior on the surface of Nd as evidenced by strong short-range order, but without the existence of long-range order. Magnetic field and temperature-dependent measurements reveal high sensitivity of the spectral weight of q-states to applied fields, without any clear unique ground state, as well as evidence of aging behavior in the magnetic state. We discuss our findings in the context of unconventional spin-glass behavior.

[1] W.C. Koehler, J. Appl. Phys. 36, 1078 (1965).
[2] R. M. Moon & R. M. Nicklow, J. Magn. Magn. Mater. 100, 139 (1991).
[3] E.M. Forgan et al., PRL 62, 470 (1989).
[4] D. Wegner et al., Phys. Rev. B 73, 165415 (2006).
[5] D. Wegner et al., Jpn. J. Appl. Phys. 45, 1941 (2006).

As this is the final theme 3 meeting of the year, we would like to invite you all to the holiday party directly after the talk on the 1st floor North side (Wing 7/8)

We hope to see you there!

Alex Khajetoorians