X-ray absorption spectroscopy; artificial multiferroics; magnetic impurities; magnetism at the nanoscale
S.R.V. Avula, J. Heidler, J. Dreiser, J. Vijayakumar, L. Howald, F. Nolting, C. Piamonteze (2018), Study of magneto-electric coupling between ultra-thin Fe films and PMN-PT using Xray magnetic circular dichroism, in Journal of Applied Physics
, 123, 064103-1-064103-5.
Singha Aparajita, Baltic Romana, Donati Fabio, Wackerlin Christian, Dreiser Jan, Persichetti Luca, Stepanow Sebastian, Gambardella Pietro, Rusponi Stefano, Brune Harald (2017), 4 f occupancy and magnetism of rare-earth atoms adsorbed on metal substrates, in PHYSICAL REVIEW B
, 96(22), 1-13.
Staub U., Rettig L., Bothschafter E. M., Windsor Y. W., Ramakrishnan M., Avula S. R. V., Dreiser J., Piamonteze C., Scagnoli V., Mukherjee S., Niedermayer C., Medarde M., Pomjakushina E. (2017), Interplay of Fe and Tm moments through the spin-reorientation transition in TmFeO3, in PHYSICAL REVIEW B
, 96(17), 1-11.
Windsor Y. W., Piamonteze C., Ramakrishnan M., Scaramucci A., Rettig L., Huever J. A., Bothschafter E. M., Bingham N. S., Alberca A., Avula S. R. V., Noheda B., Staub U. (2017), Magnetic properties of strained multiferroic CoCr2O4: A soft x-ray study, in PHYSICAL REVIEW B
, 95(22), 1-15.
Baltic Romana, Pivetta Marina, Donati Fabio, Wackerlin Christian, Singha Aparajita, Dreiser Jan, Rusponi Stefano, Brune Harald (2016), Superlattice of Single Atom Magnets on Graphene, in NANO LETTERS
, 16(12), 7610-7615.
Wackerlin Christian, Donati Fabio, Singha Aparajita, Baltic Romana, Rusponi Stefano, Diller Katharina, Patthey Francois, Pivetta Marina, Lan Yanhua, Klyatskaya Svetlana, Ruben Mario, Brune Harald, Dreiser Jan (2016), Giant Hysteresis of Single-Molecule Magnets Adsorbed on a Nonmagnetic Insulator, in ADVANCED MATERIALS
, 28(26), 5195-5195.
Singha Aparajita, Donati Fabio, Wackerlin Christian, Baltic Romana, Dreiser Jan, Pivetta Marina, Rusponi Stefano, Brune Harald (2016), Magnetic Hysteresis in Er Trimers on Cu(111), in NANO LETTERS
, 16(6), 3475-3481.
Donati F., Rusponi S., Stepanow S., Waeckerlin C., Singha A., Persichetti L., Baltic R., Diller K., Patthey F., Fernandes E., Dreiser J., Sljivancanin Z., Kummer K., Nistor C., Gambardella P., Brune H. (2016), Magnetic remanence in single atoms, in SCIENCE
, 352(6283), 318-321.
Waeckerlin Christian, Donati Fabio, Singha Aparajita, Baltic Romana, Uldry Anne-Christine, Delley Bernard, Rusponi Stefano, Dreiser Jan (2015), Strong antiferromagnetic exchange between manganese phthalocyanine and ferromagnetic europium oxide, in CHEMICAL COMMUNICATIONS
, 51(65), 12958-12961.
Bringing different materials into contact at the nanoscale opens the door to improving or creating new functionalities by tuning the properties of the resulting nanointerfaces. Nanoscale magnetic systems exhibit a variety of unusual phenomena when compared to the bulk materials, in particular when the dimensions involved are comparable to critical length scales such as the domain wall width and the exchange length. Artificial heterostructures consisting of thin films and small clusters down to single atoms, deposited in a controlled way on surfaces or embedded in a substrate are model systems to investigate the origin of the magnetic anisotropy energy (MAE) and magnetic interactions. The magnetic properties of these systems strongly depend on the atomic coordination, on the substrate electronic structure close to the Fermi level, and on the type of the interaction in the heterostructure. To understand the interaction and potential new functionalities of these coupled systems we aim in this proposal at studying the properties of two classes of systems.Project A) Artificial multiferroic systems, in which novel properties emerge from the coupling between a ferroelectric and a ferromagnetic material at the interface, are a possible route to obtain significant room temperature magnetoelectric coupling in nanoscale systems. Here, we want to understand and optimize the magnetic anisotropy of ferromagnetic thin films through the magnetoelectric coupling with a ferroelectric substrate. Further, we want to understand what happens to the coupling if dimensionality is reduced down to ferromagnetic clusters or single atoms of ferromagnetic elements.Project B) Magnetic impurities, in the form of single atoms or small clusters (less than 10 atoms) coupled to a substrate can result in high MAE. Unlike large clusters containing hundreds or more atoms, their interaction with the substrate can be relatively easily modeled. Here, we want to find which combination of magnetic atom and substrate results in the highest MAE. As substrates we will use semiconductors, which are promising due to the band gap between conduction and valence states, and graphene which is promising due its high in-plane electron mobility but mainly free sp3 bonds perpendicular to it.Our experimental approach is a combination of scanning tunneling microscopy (STM) with spatially integrating techniques, such as X-ray absorption spectroscopy (XAS) and X-ray magnetic dichroism (XMD). For this, the groups of Prof. H. Brune (EPFL) and Prof. F. Nolting (PSI) have built the X-Treme beamline at the Swiss Light Source (SLS). This beamline gives the unique opportunity of combining in a single UHV chamber a low temperature (2K) high magnetic field (7T) cryostat for XAS-XMD, a variable temperature STM (scanning tunneling microscope), a MOKE (magneto-optical Kerr effect) for in-situ characterization, and a chamber for sample cleaning and MBE growth with the sample temperature adjustable in the range 30-1600 K.We apply for the funding of two Ph.D. students, one will be located at EPFL and one at PSI, each student will focus on one of the projects but both students will participate in our beam times and therefore closely interact.