Sept. 15-20, 2019
ECASIA19: 18th European Conference on Applications of Surface and Interface Analysis
Sept. 13-20, 2019
|Summer School Spectroelectrochemistry, IFW Dresden|
|March 28/29, 2019|
|Dec. 4-5. 2018||UKRATOP Workshop, IFW Dresden|
Oct. 1 – 2, 2018
SAW Symposium, Westin Bellevue Dresden, Dresden, Germany
|Aug. 28-30, 2018||Spin , waves & interactions 2018, Greifswald, Germany|
April 8- 11, 2018
667. WE-Heraeus-Seminar on System-oriented approach to thermoelectrics: Materials – Interfaces – Devices in Bad Honnef, Germany
March 11-16, 2018
Joint Conference of the Condensed Matter Divisions of the DPG and EPS,
Feb. 1, 2018
Workshop of the DFG Priority Programme 1458 “High Temperature Superconductivity in Iron Pnictides“, IFW Dresden
Jan. 29-31, 2018
EPSQMat 2018: International Workshop on Electron and photon spectroscopies of quantum materials: status and perspectives, IFW Dresden
|Location||IFW Dresden B3E.26|
|Topic||Dynamics of vortices in 2D easy-plane magnets|
We consider a 2-dimensional classical anisotropic Heisenberg model with easy-plane symmetry, i.e. the spins prefer to lie in the plane. For small anisotropy planar vortices are unstable, but so-called “non-planar vortices” are stable. They exhibit a core in which the spins point upwards or downwards. Thus a non-planar vortex is characterized by two topolocigal charges: vorticity q and polarity p = ± 1 (core spins up or down). Both q and p are constants of motion in the continuum limit. However, in discrete spin systems the polarity can be switched in different ways: scattering with spin waves, thermal noise, a magnetic field pulse, static and rotating magnetic fields, or a spin-polarized electrical current. Only the last two cases are presented in this talk.
Two vortices on a large system show a dynamics which can be classified in 4 scenarios, depending on the choice of the charges q and p for each vortex. A vortex and an antivortex either circle around each other, or go on parallel lines. The same holds for a pair of vortices or antivortices.
The case of a vortex and an antivortex with same polarities is particularly interesting: This pair actually is a solitary wave which propagates with constant velocity. When two such pairs make a head-on collision several very distinct scenarios can appear.
Finally we investigate polarity switching by a spin-polarized electric current. Here a complicated scenario exists in which a vortex-antivortex pair is created and interacts with the original vortex such that finally a new vortex with opposite polarity remains.
|Invited by||Dr. Volodymyr Kravchuk|
|Location||IFW Dresden B3E.26|
|Topic||Next-Generation Ultrafast Transmission Electron Microscopy - Development and Applications|
|Invited by||Prof. Dr. Bernd Büchner, Dr. Axel Lubk|
|Location||IFW Dresden A2E.30|
|Topic||Characterization of the SYK quantum dots|
|Invited by||Dr. Flavio de Souza Nogueira|
|Location||Leibniz IFW Dresden D2E.27|
|Topic||Probing magnetic microtextures on the nanoscale|
Magnetic force microscopy (MFM) has established its place as an extremely valuable method for the investigation of magnetic microstructures on the nanometer scale. Beyond being a purely qualitative imaging technique, quantitative MFM has the capability to locally measure the stray fields and eventually provide quantitative input data for a reconstruction of the underlying magnetization structure. This requires a full calibration of the imaging properties of the MFM tip and the most general approach is through the determination of the so-called tip transfer function (TTF) in Fourier space [1-3]. A calibrated tip transforms MFM signals into true stray field values on the nanometer scale. Furthermore, the field profile is corrected for the tip broadening and thus allows a true size determination of isolated magnetic objects. Reconstructing the magnetization texture from the stray field landscape will need additional knowledge on the sample. Here, micromagnetic simulations can help by providing valid initial magnetization models.
I will report on our activities within a current European metrology project  to establish materials, measurement protocols and analysis procedures for a routine application of qMFM and will present various examples, which demonstrate the large benefit of treating MFM data quantitatively. These examples range from vortex states at nanowires and thin films to flux lines in superconductors and to optically written domains in magnetic data storage media .
 Hug et al. JAP 83 (1998),  Vock et al. APL 105 (2014),  Panchal et al. Sci. Rep. 7 (2017).  EMPIR 15SIB06 NanoMag  John et al., Sci. Rep. 7 (2017).
|Invited by||Prof. Dr. Oliver G. Schmidt|
|Location||IFW Dresden D2E.27|
|Topic||Layered chromium trihalides CrX3 (X=Cl, Br, I): synthesis and simulation by chemical vapor growth of bulk flakes and nanosheets|
|Invited by||Prof. Dr. Bernd Büchner|
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