Magneto-Optical Spectroscopy
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Semiconductor Physics
MAGNETO-OPTICAL SPECTROSCOPY
MAGNETO-OPTICAL SPECTROSCOPY
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Nano MOKE: Wavelength 632 nm.
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MOKE Spectrometer & RAS: Maximum field ~2T.
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Magneto-optical cryostat for electrical measurements:
Maximum field 7T.
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Organic field effect transistor and magnetoresistance measurement setup:
Magnetic field up to ~0.5T.
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Quadrupol electromagnet:
Magnetic field up to:
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Magneto-optical properties of molecules: Paramagnetic and diamagnetic molecules can exhibit magneto-optical activity in the UV-vis spectral range. From MOKE spectra and spectroscopic ellipsometry data, the Voigt constant Q, which is a material parameter independent of the film thickness, can be extracted. Using Q, the magneto-optical effects like MOKE or Faraday effect can be calculated. For example, Tetramethoxy-phenylporphyrins (TMPPs) show magneto-optical activity at around 2 eV (Q-band) and 3 eV (B-band). These molecules were synthesized by the Inorganic Chemistry Group at the Chemnitz University of Technology. |
Chiral biomolecules on magnetic substrates: The adsorption of chiral molecules was recently shown to trigger a change in the magnetisation of mesoscopic magnetic domains in a ferromagnetic underlayer. In this work, we investigated the macroscopic (magneto-)optical response of chemisorbed α‑helical polyalanine self-assembled monolayers (SAMs) on a gold and gold-capped-cobalt thin film on Au substrates using spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy and microscopy. The optical and magneto-optical spectra reveal selective chemisorption of the α‑helical polyalanine molecules depending on the orientation of the substrate remanent magnetisation during the SAMs process. Moreover, a flipping of the magneto-optical response was observed in some of the magnetic substrates after the chiral SAMs formation. J. Mater. Chem. C,8, (2020), 11822-118291,
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Magneto-optical properties of transition metal oxides: Nickel ferrite (NiFe2O4) shows feature-rich magneto-optical activity throughout the UV-Vis spectral range. There are three types of electronic transitions in the material that show up as pronounced peaks in the MOKE spectrum: transitions between crystal field splitted d-orbitals (CF), inter-sublattice charge transfer transitions (ISCT) and intervalance charge transfer transitions (IVCT). MOKE-magnetometery measurements reveal the typical ferrimagnetic magnetization behavior of NiFe2O4 with a remanence of approx. 40% and a coercivity of only ±80 mT. The samples were prepared by spin coating from an aqueous precursor solution with subsequent annealing to 1000 °C in the labs of Assoc. Prof. Page (University of Oregon, Eugene, OR, USA).
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Crystallisation of optically thick films of CoxFe(80-x)B20: evolution of the (magneto-) optical and structural properties: CoFeB alloys are highly relevant materials for spintronic applications. In this work, the crystallisation of CoFeB alloys triggered by thermal annealing was investigated by x-ray diffraction techniques and SEM, as well as spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy for annealing temperatures ranging from 300°C to 600°C. The transformation of ~100 nm thick CoxFe(80-x)B20 films from amorphous to polycrystalline was revealed by the sharpening of spectral features observed in optical and magneto-optical dielectric functions spectra. The influence of B on the dielectric function was assessed both experimentally and by optical modelling. By analysing the Drude component of the optical dielectric function, a consistent trend between the charge carrier scattering time/resistivity and the annealing temperature was observed, in agreement with the electrical investigations by means of the four-point-probe method. Phys. Rev. B 101, (2020), 054438, https
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Apoorva Sharma, Patrick Matthes, Ivan Soldatov, Sri Sai Phani Kanth Arekapudi, Benny Böhm, Marina Lindner, Oleksandr Selyshchev, Nguyen Thi Ngoc Ha,
Michael Mehring, Christoph Tegenkamp, Stefan E. Schulz, Dietrich R.T. Zahn, Yossi Paltiel, Olav Hellwig, Georgeta Salvan Apoorva Sharma, Maria A. Hoffmann, Patrick Matthes, Olav Hellwig, Cornelia Kowol, Stefan E. Schulz, Dietrich R.T. Zahn, Georgeta Salvan Patrick Thoma, Manuel Monecke, Oana-Maria Buja, Dmytro Solonenko, Roxana Dudric, Oana-Tereza Ciubotariu, Manfred Albrecht, Iosif G. Deac,
Romulus Tetean, Dietrich R.T.Zahn, Georgeta Salvan Sreetama Banerjee, Daniel Bülz, Dmytro Solonenko, Danny Reuter, Carsten Deibel, Karla Hiller, Dietrich R.T. Zahn, Georgeta Salvan Peter Richter, Paul N. Plassmeyer, Julia Harzdorf, Tobias Rüffer, Heinrich Lang, Jana Kalbacova, Nathanael Jöhrmann, Steffen Schulze, Michael Hietschold,
Sri Sai Phani Kanth Arekapudi, Manfred Albrecht, Dietrich R.T. Zahn, Catherine J. Page, Georgeta Salvan Tobias Birnbaum, Torsten Hahn, Claudia Martin, Jens Kortus, Michael Fronk, Frank Lungwitz, Dietrich R.T. Zahn, Georgeta Salvan Cameliu Himcinschi, Ionela Vrejoiu, Georgeta Salvan, Michael Fronk, Andreas Talkenberger, Dietrich R. T. Zahn, David Rafaja, and Jens Kortus |
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