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Michalis Charilaou

PhD, ETH Zurich, Switzerland (2012)
Diploma in Physics, FU Berlin, Germany (2009)

PHYS 201: Mechanics, Waves & Thermodynamics
PHYS 460G & 591: Fundamentals & Methods of Nanoscience


Research activities

Modeling of magnetization textures in nanostructures

Magnetic nano-objects play an ever increasing role in a wide range of technologies, and their dimensionality is continuously decreasing. On the nanoscale, the competition between different magnetic forces can lead to the formation of topologically non-trivial magnetization textures in the form of quasiparticles, such as domain walls, skyrmions, and Bloch points. The presence and dynamics of these quasiparticle textures generates emergent electromagnetism and can lead to striking phenomena, such as the generation of terahertz radiation. We study these phenomena by means of atomistic and high-resolution micromagnetic simulations with the goal of unravelling the interplay of magnetic forces in fundamental length scales of magnetic matter and to identify the characteristics of emergent magnetic phenomena. One example is the computational observation of hedgehogs, or Bloch points, in ferromagnetic nanowires, where upon the application of an external field, skyrmion tubes are created, and Bloch-point pairs are created once the skyrmion tubes break, as illustrated in the figure above (taken from Physical Review Letters v. 121, p. 097202, 2018).


Magnetic nanoparticles in earth systems

Iron oxide or sulfide nanoparticles are omnipresent in geological systems and can be found in a wide range of sediments, e.g. due to bacteria or in hydrocarbon environments. The study of the physics of arrangements of magnetic nanoparticles provides us with the opportunity to correlate magnetism with the planet’s history and at the same time to infer environmental conditions based on the abundance of magnetic intensity. Special focus has been placed on the study of magnetotactic bacteria (MTB), as seen in the figure here (taken from Applied Physics Letters v. 104, p. 112406, 2014), where ferromagnetic resonance spectroscopy experiments and theoretical modeling have been combined to study the statics and dynamics of linear arrangements of magnetic nanoparticles. These techniques can be applied in a wide range of applications, ranging from oil and gas exploration to biomedical imaging and therapy, and therefore seeking a deeper understanding of such nanoparticle systems is crucial.


List of publications

L. Pierobon, C. Moutafis, Y. Li, J. F. Löffler, M. Charilaou
Collective antiskyrmion-mediated phase transition and defect-induced melting in chiral magnetic films
Scientific Reports 8, 16675 (2019)
doi: 10.1038/s41598-018-34526-0

D. Koulialias, P. G. Weidler, M. Charilaou, J. F. Löffler and A. U. Gehring
Cation diffusion patterns across the magneto-structural transition in Fe7S8
Physical Chemistry Chemical Physics 21, 13040 (2019)
doi: 10.1039/c9cp01387c

D. Koulialias, E. Canévet, M. Charilaou, P. G. Weidler, J. F. Löffler and A. U. Gehring
The relation between local structural distortion and the low-temperature magnetic anomaly in Fe7S8
Journal of Physics: Condensed Matter 30, 425803 (2018)
doi: 10.1088/1361-648x/aadf54

M. Charilaou, H.-B. Braun, J. F. Löffler
Monopole-induced Emergent Electric Fields in Ferromagnetic Nanowires
Physical Review Letters 121, 097202 (2018)
doi: 10.1103/PhysRevLett.121.097202

H.-W. Huang, T.-Y. Huang, M. Charilaou, S. Lyttle, Q. Zhang, S. Pane, B. J. Nelson
Investigation of Magnetotaxis of Reconfigurable Micro-Origami  Swimmers with Competitive and Cooperative Anisotropy
Advanced Functional Materials 1802110 (2018)
doi: 10.1002/adfm.201802110

D. Koulialias, M. Charilaou, C. Mensing, J. F. Löffler, A. U. Gehring:
Torque analysis of incoherent spin rotation in the presence of ordered defects
Applied Physics Letters 112, 202404 (2018)
doi: 10.1063/1.5023886

D. Koulialias, M. Charilaou, E. Schäublin, C. Mensing, P. G. Weidler, J. F. Löffler, A. U. Gehring:
Ordered defects in Fe-S generate additional magnetic anisotropy symmetries
Journal of Applied Physics 123, 033902 (2018)
doi: 10.1063/1.5007830

M. Charilaou
Ferromagnetic resonance of biogenic nanoparticle-chains
Journal of Applied Physics 122, 063903 (2017)
doi: 10.1063/1.4987034

M. Charilaou & J. F. Löffler
Skyrmion oscillations in magnetic nanorods with chiral interactions
Physical Review B 95, 024409 (2017)
doi: 10.1103/PhysRevB.95.024409

M. Charilaou, C. Bordel, B. B. Maranville, P.-E. Berche, P. Fischer, F. Hellman:
Magnetic properties of ultrathin discontinuous Co/Pt multilayers: Comparisson
with short-range ordered and isotropic CoPt3 films
Physical Review B 93, 224408 (2016)
doi: 10.1103/PhysRevB.93.224408

D. Koulialias, I. García-Rubio, L. Rahn-Lee, A. Komeili, J. F. Löffler, A. U. Gehring, M. Charilaou:
Competitive and cooperative anisotropy in magnetic nanocrystal chains of
magnetotactic bacteria
Journal of Applied Physics 120, 083901 (2016)
doi: 10.1063/1.4961321

D. Koulialias, J. Kind, M. Charilaou, P. G. Weidler, J. F. Löffler, A. U. Gehring:
Variable defect structures cause the magnetic low-temperature transition in
natural monoclinic pyrrhotite
Geophysical Journal International 204, 961 (2016)
doi: 10.1093/gji/ggv498

M. Charilaou, L. Rahn-Lee, J. Kind, I. García-Rubio, A. Komeili, A. U. Gehring:
Anisotropy of Bullet-Shaped Magnetite Nanoparticles in the Magnetotactic
Bacteria Desulfovibrio magneticus sp. Stain RS-1
Biophysical Journal 108, 1268-1274 (2015)
doi: 10.1016/j.bpj.2015.01.007

M. Charilaou and F. Hellman:
Roughness effects in uncompensated antiferromagnets
Journal of Applied Physics 117, 083907 (2015)
doi: 10.1063/1.4913594

M. Charilaou and F. Hellman:
Surface-induced phenomena in uncompensated collinear antiferromagnets
Journal of Physics: Condensed Matter 27, 086001 (2015)
doi: 10.1088/0953-8984/27/8/086001

M. Charilaou, J. Kind, D. Koulialias, P. G. Weidler, C. Mensing, J. F. Löffler, A. U. Gehring:
Magneto-electronic coupling in modulated defect-structures of natural Fe 1−x S
Journal of Applied Physics 118, 083903 (2015)
doi: 10.1063/1.4929634

M. Charilaou, C. Bordel, F. Hellman:
Magnetization switching and inverted hysteresis in antiferromagnetic 
Applied Physics Letters 104, 212405 (2014)
doi: 10.1063/1.4880821

M. Charilaou and F. Hellman:
Anomalous magnetic thermodynamics in collinear antiferromagnets
Europhysics Letters 107, 27002 (2014)
doi: 10.1209/0295-5075/107/27002

M. Charilaou, J. Kind, I. García-Rubio, D. Schüler, A. U. Gehring:
Magnetic anisotropy of non-interacting collinear nanocrystal-chains
Applied Physics Letters 104, 112406 (2014)
doi: 10.1063/1.4869092

H.-J. Lee, C. Bordel, J. Karel, D. W. Cooke, M. Charilaou, F. Hellman:
Electron-mediated ferromagnetic behavior in CoO/ZnO multilayers
Physical Review Letters 110, 087206 (2013)
doi: 10.1103/PhysRevLett.110.087206

M. Charilaou and F. Hellman:
Mean-field simulation of metal oxide antiferromagnetic films and multilayers
Physical Review B 87, 184433 (2013)
doi: 10.1103/PhysRevB.87.184433

J. Kind, I. García-Rubio, M. Charilaou, N. R. Nowaczyk, J. F. Löffler, A. U. Gehring:
Domain-wall dynamics in 4C pyrrhotite at low temperature
Geophysical Journal International 195, 192–199 (2013)
doi: 10.1093/gji/ggt262

U. Gehring, J. Kind, M. Charilaou, I. García-Rubio:
S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils
Journal of the Royal Society Interface 10, 20120790 (2012)
doi: 10.1098/rsif.2012.0790

M. Charilaou, J. F. Löffler, A. U. Gehring:
Magnetic thermodynamics as proxy for chemical inhomogeneity in
hemo-ilmenite solid solutions
Physics and Chemistry of Minerals 39, 87 (2012)
doi: 10.1007/s00269-011-0463-y

U. Gehring, M. Charilaou, and I. García-Rubio:
Oxidized magnetosomes in magnetotactic bacteria
Journal of Magnetism and Magnetic Materials 324, 1281 (2012)
doi: 10.1016/j.jmmm.2011.10.039

R. M. Erb, J. Segmehl, M. Charilaou, J. F. Löffler, and A. R. Studart:
Non-linear alignment dynamics in suspensions of platelets under rotating
magnetic fields
Soft Matter 8, 7604 (2012)
doi: 10.1039/C2SM25650A

M. Charilaou, K. K. Sahu, A. U. Gehring, and J. F. Löffler:
Steep energy landscapes and adjustable magnetization states in a four-layer
mean-field model with competing interactions
Physical Review B 86, 104415 (2012)
doi: 10.1103/PhysRevB.86.104415

M. Charilaou, D. Sheptyakov, J. F. Löffler, A. U. Gehring:
Large spontaneous magnetostriction in FeTiO3 and adjustable magnetic   
configuration in Fe(III)-doped FeTiO3
Physical Review B 86, 024439 (2012)
doi: 10.1103/PhysRevB.86.024439

M. Charilaou, K. K. Sahu, S. Zhao, J. F. Löffler, A. U. Gehring:
Interaction-induced partitioning and magnetization jumps in mixed-spin oxide
FeTiO 3 - Fe 2 O 3
Physical Review Letters 107, 057202 (2011)
doi: 10.1103/PhysRevLett.107.057202

M. Charilaou, J. F. Löffler, A. U. Gehring:
Slow dynamics and field-induced transitions in a mixed-valence oxide solid
Physical Review B 83, 224414 (2011)
doi: 10.1103/PhysRevB.83.224414

M. Charilaou, K. K. Sahu, D. Faivre, A. Fischer, I. García-Rubio, A. U. Gehring:
Evolution of magnetic anisotropy and thermal stability during nanocrystal-chain
Applied Physics Letters 99, 182504 (2011)
doi: 10.1063/1.3658387

M. Charilaou, K. K. Sahu, A. U. Gehring, J. F. Löffler:
Monte-Carlo study of partitioning mechanisms in mixed-spin systems
Physical Review B 84, 224434 (2011)
doi: 10.1103/PhysRevB.84.224434

M. Charilaou, M. Winklhofer, A. U. Gehring:
Simulation of ferromagnetic resonance spectra of linear chains of magnetite
Journal of Applied Physics 109, 093903 (2011)
doi: 10.1063/1.358110

U. Gehring, J. Kind, M. Charilaou, I. García-Rubio:
The detection of magnetotactic bacteria and magnetofossils by means of magnetic
Earth and Planetary Science Letters 309, 113–117 (2011)
doi: 10.1016/j.epsl.2011.06.024

U. Gehring, H. Fischer, M. Charilaou, I. García-Rubio:
Magnetic anisotropy and Verwey transition of magnetosome chains in
Magnetospyrillum gryphiswaldense
Geophysical Journal International 187, 1215–1221 (2011)
doi: 10.1111/j.1365-246X.2011.05175.x

M. Charilaou, J. F. Löffler, A. U. Gehring:
Fe-Ti-O exchange at high temperature and thermal hysteresis
Geophysical Journal International 185, 647–652 (2011)
doi: 10.1111/j.1365-246X.2011.04981.x

M. Charilaou, K. Lenz, W. Kuch:
Spin-pumping-enhanced magnetic damping in ultrathin Cu(001)/Co/Cu and
Cu(001)/Ni/Cu films
Journal of Magnetism and Magnetic Matererials 322, 2065 (2010)
doi: 10.1016/j.jmmm.2010.01.035

E. Th. Papaioannou, K. Lenz, M. Charilaou, P. Fumagalli, P. Poulopoulos, M Angelakeris, N. K. Flevaris, F. Wilhelm, A. Rogalev:
CoCr/Pt multilayers with adjustable perpendicular anisotropy
Journal of Applied Physics 103, 093905 (2008)
doi: 10.1063/1.2912948