Mitarbeiter

Name: Dr. Katharina Ollefs
Emailadresse:

Diplom-/Masterarbeit:
Structure and Magnetic Correlations in Nanoengineered Systems

Publikationsliste von Dr. Katharina Ollefs
2023
29 - Spatially-resolved dynamic sampling of different phasic magnetic resonances of nanoparticle ensembles in a magnetotactic bacterium Magnetospirillum Magnetotacticum
T. Feggeler, J. Lill, D. Günzing, R. Meckenstock, D. Spoddig, M. V. Efremova, S. Wintz, M. Weigand, B. W. Zingsem, M. Farle, H. Wende, K. J. Ollefs, Hendrik Ohldag
New Journal of Physic NJP-115578.R1, (2023) DOI: 10.1088/1367-2630/acc81f
28 - Evaluation protocol for revealing magnonic contrast in TR-STXM measurements
B. Zingsem, Thomas Feggeler, Ralf Meckenstock, Detlef Spoddig, Taddäus Schaffers, Santa Pile, Hendrik Ohldag, Michael Farle, Heiko Wende, Andreas Ney, Katharina Ollefs
AIP Advances 13, (2023) DOI: 10.1063/5.0145753
2022
27 - Element-specific visualization of dynamic magnetic coupling in a Co/Py bilayer microstructure
T. Feggeler, Ralf Meckenstock, Detlef Spoddig, Christian Schoeppner, Benjamin Zingsem, Taddaeus Schaffers, Hendrik Ohldag, Heiko Wende, Michael Farle, Andreas Ney, Katharina Ollefs
Scientific Reports 12, 18724 (2022) DOI: 10.1038/s41598-022-23273-y
2021
26 - Spatially resolved GHz magnetization dynamics of a magnetite nano-particle chain inside a magnetotactic bacterium
Thomas Feggeler, Ralf Meckenstock, Detlef Spoddig, Benjamin W. Zingsem, Hendrik Ohldag, Heiko Wende, Michael Farle, Michael Winklhofer and Katharina Ollefs
Physical Review Research 3, 033036 (2021) DOI: 10.1103/PhysRevResearch.3.033036
2020
25 - Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation
S. Pile, T. Feggeler, T. Schaffers, R. Meckenstock, M. Buchner, D. Spoddig, B. Zingsem, V. Ney, M. Farle, H. Wende, H. Ohldag, A. Ney and K. Ollefs
Applied Physics Letters 116(7), 072401-1 (2020) DOI: 10.1063/1.5139881
2019
24 - Extracting the Dynamic Magnetic Contrast in Time-Resolved X-Ray Transmission Microscopy
T. Schaffers, T. Feggeler, S. Pile, R. Meckenstock, M. Buchner, D. Spoddig, V. Ney, M. Farle, H. Wende, S. Wintz, M. Weigand, H. Ohldag, K. Ollefs and A. Ney
Nanomaterials-Basel 9(7), 940 (2019) DOI: 10.3390/nano9070940
2018
23 - Hysteresis Design of Magnetocaloric Materials - From Basic Mechanisms to Applications
F. Scheibel, T. Gottschall, A. Taubel, M. Fries, K. P. Skokov, A. Terwey, W. Keune, K. Ollefs, H. Wende, M. Farle, M. Acet, O. Gutfleisch, M. E. Gruner
Energy Technol. 6, 1397 (2018) DOI: 10.1002/ente.201800264
2017
22 - The combination of micro-resonators with spatially resolved ferromagnetic resonance
T. Schaffers, R. Meckenstock, D. Spoddig, T. Feggeler, K. Ollefs, C. Schppner, S. Bonetti, H. Ohldag, M. Farle, and A. Ney
Rev. Sci. Instrum. 88, 093703 (2017) DOI: 10.1063/1.4996780
2015
21 - Toward broad-band x-ray detected ferromagnetic resonance in longitudinal geometry
K. Ollefs, R. Meckenstock, D. Spoddig, F. M. Rmer, Ch. Hassel, Ch. Schppner, V. Ney, M. Farle, A. Ney
Journal of Applied Physics 117, 223906 (2015) DOI: 10.1063/1.4922248
20 - Magnetic ordering in magnetic shape memory alloy Ni-Mn-In-Co
K. Ollefs, Ch. Schppner, I. Titov, R. Meckenstock, F. Wilhelm, A. Rogalev, J. Liu, O. Gutfleisch, M. Farle, H. Wende, and M. Acet
Physical Review B 92, 224429 (2015)
19 - Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 510 GHz frequency range
Stefano Bonetti, Roopali Kukreja, Zhao Chen, Detlef Spoddig, Katharina Ollefs, Christian Schppner, Ralf Meckenstock, Andreas Ney, Jude Pinto, Richard Houanche, Josef Frisch, Joachim Sthr, Hermann A. Drr, Hendrik Ohldag
Rev. Sci. Instrum. 86, 093703 (2015) DOI: 10.1063/1.4930007
2012
18 - Structural and magnetic analysis of epitaxial films of Gd-doped ZnO
V. Ney, S. Ye, T. Kammermeier, K. Ollefs, F. Wilhelm, A. Rogalev, S. Lebgue, A. L. da Rosa, and A. Ney
Phys. Rev. B 85, 235203 (2012) DOI: 10.1103/PhysRevB.85.235203
17 - Effects of the Inhomogenous Co Doping on the Magnetoresistance of Zn1−xCoxO Epitaxial Films
S. Ye, L. Klar, A. Ney, V. Ney, T. Kammermeier, K. Ollefs, F. Liu and G. Wang
Journal of Nanoscience and Nanotechnology 2, 1054 (2012) DOI: 10.1166/jnn.2012.4266
2011
16 - Structural, chemical and magnetic properties of secondary phases in Co-doped ZnO
A. Ney, A. Kovcs, V. Ney, S. Ye, K. Ollefs, T. Kammermeier, F. Wilhelm, A. Rogalev and R. E. Dunin-Borkowski
New J. Phys. 13, 103001 (2011) DOI: 10.1088/1367-2630/13/10/103001
15 - Element-Specific Magnetic Hysteresis of Individual 18 nm Fe Nanocubes
F. Kronast, N. Friedenberger, K. Ollefs, S. Gliga, L. Tati-Bismaths, R. Thies, A. Ney, R. Weber, C. Hassel, F. M. Rmer, A. V. Trunova, C. Wirtz, R. Hertel, H. A. Drr and M. Farle
Nano Lett. 11, 1710 (2011) DOI: 10.1021/nl200242c
2010
14 - Co-Doped ZnO Epitaxial Films: From a Brillouin-Like Paramagnet to a Phase-Separated Superparamagnetic Ensemble
V. Ney, S. Ye, K. Ollefs, T. Kammermeier, F. Wilhelm, A. Rogalev, and A. Ney
J. Nanosci. Nanotechnol. 10, 5958 (2010) DOI: 10.1166/jnn.2010.2590
13 - Magnetism of Co doped ZnO with Al codoping: Carrier-induced mechanisms versus extrinsic origins
A. Ney, V. Ney, S. Ye, K. Ollefs, T. Kammermeier, T. C. Kaspar, S. A. Chambers, F. Wilhelm and A. Rogalev
Phys. Rev. B 82, 041202(R) (2010) DOI: 10.1103/PhysRevB.82.041202
12 - High-resolution x-ray lensless imaging by differential holographic encoding
D. Zhu, M. Guizar- Sicairos, B. Wu, A. Scherz, Y. Acremann, T. Tyliszczak, P. Fischer, N. Friedenberger, K. Ollefs, M. Farle, J. R. Fienup, and J. Stohr
Phys. Rev. Lett. 105, 043901 (2010) DOI: 10.1103/PhysRevLett.105.043901
11 - Influence of the developing magnetic order on the transport properties of epitaxial Zn1-xCoxO films
S. Ye, V. Ney, T. Kammermeier, K. Ollefs, S. Zhou, H. Schmidt, A. Ney
J. Phys.: Conference Series 200, 052034 (2010) DOI: 10.1088/1742-6596/200/5/052034
10 - Anisotropic paramagnetism of Co-doped ZnO epitaxial films
A. Ney, T. Kammermeier, K. Ollefs, S. Ye, V. Ney, T. C. Kaspar, S. A. Chambers, F. Wilhelm and A. Rogalev
Phys. Rev. B 81, 054420 (2010) DOI: 10.1103/PhysRevB.81.054420
9 - Advanced spectroscopic synchrotron techniques to unravel the intrinsic properties of dilute magnetic oxides: the case of Co:ZnO
A. Ney, M. Opel, T. C. Kaspar, V. Ney, S. Ye, K. Ollefs, T. Kammermeier, S. Bauer, K.-W. Nielsen, S. T. B. Goennenwein, M. H. Engelhard, S. Zhou, K. Potzger, J. Simon, W. Mader, S. M. Heald, J. C. Cezar, F. Wilhelm, A. Rogalev, R. Gross and S. A. Chambers
New J. Phys. 12, 013020 (2010) DOI: 10.1088/1367-2630/12/1/013020
8 - Tuning the magnetic properties of Zn1-xCoxO films
V. Ney, S. Ye, T. Kammermeier, K. Ollefs, A. Ney, T.C. Kaspar, S.A. Chambers, F. Wilhelm and A. Rogalev
J. Magn. Magn. Mater. 322, 1232 (2010) DOI: 10.1016/j.jmmm.2009.04.024
7 - Gd-doped GaN studied with element specifity: very small polarization of Ga, paramagnetism of Gd and the formation of magnetic clusters
A. Ney, T. Kammermeier, K. Ollefs, V. Ney, S. Ye, S. Dhar, K. H. Ploog, M. Rver, J. Malindretos, A. Rizzi, F. Wilhelm, A. Rogalev
J. Magn. Magn. Mater. 322, 1162 (2010) DOI: 10.1016/j.jmmm.2009.06.033
6 - Observation of the Onset of Magnetic Clustering in Superparamagnetic Zn1-xCoxO Films
S. Ye, V. Ney , T. Kammermeier, K. Ollefs, A. Ney, F. Wilhelm and A. Rogalev
J. Supercond. Nov. Magn. 23, 91 (2010) DOI: 10.1007/s10948-009-0566-6
2009
5 - Absence of ferromagnetic-transport signatures in epitaxial paramagnetic and superparamagnetic Zn0.95Co0.05O films
S. Ye, V. Ney, T. Kammermeier, K. Ollefs, S. Zhou, H. Schmidt, F. Wilhelm, A. Rogalev, and A. Ney
Phys. Rev. B 80, 245321 (2009) DOI: 10.1103/PhysRevB.80.245321
4 - Element specific measurements of the structural properties and magnetism of CoxZn1-xO
T. Kammermeier, V. Ney, S. Ye, K. Ollefs, T. C. Kaspar, S. A. Chambers, F.Wilhelm, A. Rogalev, and A. Ney
J. Magn. Magn. Mater. 321, 699 (2009) DOI: 10.1016/j.jmmm.2008.11.028
2008
3 - Limitations of measuring small magnetic signals of samples deposited on a diamagnetic substrate
A. Ney, T. Kammermeier, V. Ney, K. Ollefs, and S. Ye
J. Magn. Magn. Mater. 320, 3341 (2008) DOI: 10.1016/j.jmmm.2008.07.008
2 - Element specific magnetic properties of Gd:GaN: very small polarization of Ga and paramagnetism of Gd
A. Ney, T. Kammermeier, V. Ney, S. Ye, K. Ollefs, E. Manuel, S. Dhar, K. H. Ploog, E. Arenholz, F. Wilhelm, and A. Rogalev
Phys. Rev. B 77, 233308 (2008) DOI: 10.1103/PhysRevB.77.233308
1 - Absence of intrinsic ferromagnetic interactions of isolated and paired Co dopant atoms in Zn1-xCoxO with high structural perfection
A. Ney, K. Ollefs, S. Ye, T. Kammermeier, V. Ney, T. C. Kaspar, S. A. Chambers, F. Wilhelm, and A. Rogalev
Phys. Rev. Lett. 100, 157201 (2008) DOI: 10.1103/PhysRevLett.100.157201