Dr. Karl-Wilhelm Nielsen

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Assignments

Alumnus/Alumna: Thin Film Technology
Alumnus/Alumna: Magnetism and Spintronics

Karl-Wilhelm Nielsen was member of the Gross group at WMI as a Master and Ph.D. student between 2002 and 2008.

Master Thesis: Mn-dotiertes ZnO: ein magnetischer Halbleiter (2003)
Ph.D. Thesis: Ursache der magnetischen Kopplung in Kobalt-dotiertem ZnO (2008)

In his Ph.D. thesis, Karl-Wilhelm Nielsen studied the question, whether or not the semiconductor ZnO can be made ferromagnetic by Co doping. To address this question, he fabricated epitaxial thin films of Co-doped ZnO on ((0001) ZnO, (0001) Al₂O₃ und (0001) ScAlMgO₄ substrates and characterized them by SQUID magnetometry, magnetotransport experiments, as well as XRD and TEM. He could clearly show that the ferromagnetic-like behavior is not due to an intrinsic magnetic ordering in a diluted magnetic semiconductor but due to nm-sized super-paramagnetic Co clusters forming during epitaxial growth.

Publications of Dr. Karl-Wilhelm Nielsen

2011

Novel Multifunctional Materials Based on Oxide Thin Films and Artificial Heteroepitaxial Multilayers

Research Article | Physica Status Solidi A 208, 232-251 (2011)

M. Opel, S. Geprägs, E.P. Menzel, A. Nielsen, D. Reisinger, K.-W. Nielsen, A. Brandlmaier, F.D. Czeschka, M. Althammer, M. Weiler, S.T.B. Goennenwein, J. Simon, M. Svete, Wentao Yu, S.-M. Hühne, W. Mader, and R. Gross

2010

Advanced Spectroscopic Synchrotron Techniques to Unravel the Intrinsic Properties of Dilute Magnetic Oxides: the Case of Co:ZnO

Research Article | New J. Phys. 12, 013020 (2010)

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

2008

Nanosized superparamagnetic precipitates in cobalt-doped ZnO

Research Article | Eur. Phys. J. B 63, 437-444 (2008)

M. Opel, K.-W. Nielsen, S. Bauer, S.T.B. Goennenwein, J.C. Cezar, D. Schmeisser, J. Simon, W. Mader and R. Gross

Ursache der magnetischen Kopplung in Kobalt-dotiertem ZnO

PHD Thesis | Technical University of Munich (2008)

Karl-Wilhelm Nielsen

2006

Ferromagnetism in epitaxial Zn_0.95Co_0.05O films grown on ZnO and Al₂O₃

Research Article | physica status solidi (a) 203, 3581-3596 (2006)

K. Nielsen, S. Bauer, M. Lübbe, S.T.B. Gönnenwein, M. Opel, J. Simon, W. Mader & R. Gross

Room-temperature ferromagnetic Mn-alloyed ZnO films obtained by pulsed laser deposition

Research Article | Journal of Magnetism and Magnetic Materials 307, 212-221 (2006)

M. Diaconu, H. Schmidt, H. Hochmuth, M. Lorenz, G. Benndorf, D. Spemann, A. Setzer, P. Esquinazi, A. Poppl, H. von Wenckstern, K.-W. Nielsen, R. Gross, H. Schmid, W. Mader, G. Wagner & M. Grundmann

Weak ferromagnetism in textured Zn_1-x(TM)_xO thin films

Research Article | Superlattices and Microstructures 39, 334-339 (2006)

H. Schmidt, M. Diaconu, H. Hochmuth, M. Lorenz, A. Setzer, P. Esquinazi, A. Poppl, D. Spemann, K.-W. Nielsen, R. Gross, G. Wagner, M. Grundmann

2005

Ferromagnetism in Mn-doped ZnO due to impurity bands

Research Article | Superlattices and Microstructures 37, 327-332 (2005)

K.-W. Nielsen, J.B. Philipp, M. Opel, A. Erb, J. Simon, L. Alff & R. Gross

UV optical properties of ferromagnetic Mn-doped ZnO thin films grown by PLD

Research Article | Thin Solid Films 486, 117-121 (2005)

M. Diaconu, H. Schmidt, H. Hochmuth, M. Lorenz, G. Benndorf, J. Lenzner, D. Spemann, A. Setzer, K.-W. Nielsen, P. Esquinazi, M. Grundmann

2003

Mn-dotiertes ZnO: ein magnetischer Halbleiter

Master Thesis | Technical University of Munich (2003)