Challenges in understanding single magnetic atom systems

Orateur : Timofey BALASHOV (Karlsruhe Institute of Technology)

In the last 10 years huge advances have been made in characterizing and understanding magnetic properties of single atom magnets adsorbed on surfaces. With scanning tunneling microscopy and spectroscopy (STM & STS) as the method of choice the atoms can be addressed, manipulated and excited. As our understanding of the systems has p rogressed, so have our requirements for the experimental setup. Nowadays very high stability and energy resolution below 100 µeV are required to resolve single excitations and to ensure correct interpretation of experimental data. A newly developed compact experimental setup for STM and STS at 20 mK will be presented. To achieve this temperature, the microscope is mounted in a bath cryostat containing a 3He/4He dilution system. High mechanical stability and low electronic noise ensure a high energy resolution below 50 μeV. Additional capabilities include a 6 T axial magnetic field, quick tip and sample exchange and deposition of materials at low temperatures. Measurements using this setup on two systems will be shown. First is a single Fe atom on Pt(111) surface, where we reconcile experimental results from 2009 and 2013, and show how resolution limits affect the interpretation of STS spectra. The second system, a 3d metal β-diketonate molecule, demonstrates how the environment of a magnetic atom can be analyzed and manipulated using STM.

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