We propose to investigate ultrafast, non-equilibrium spin dynamics triggered by femtosecond optical pulses and to exploit tailored nanoscale heterogeneities in magnetic systems to control their magnetic response on an ultrafast time scale. The heterogeneities are of three different types:

1. Chemical: engineered multilayers of chemically distinct magnetic and non-magnetic materials lead to optimized optically induced spin currents, tuned interfacial spin orbit coupling and controlled interlayer exchange coupling. Lateral chemical inhomogeneities in ferrimagnets influence all optical switching (AOS).
2. Magnetic: lateral nanoscale networks of magnetic domains act as a chemically homogenous spin-valve system to study fundamental properties of spin transport. Magnetic domain nucleation and growth upon laser excitation defines AOS.
3. Excitation: tailored optical excitation via nanoscale metallic proximity masks gives a handle to control efficiency and lateral gradient of the optical stimulus and allows for subwavelength control of magnetic order.

Our main experimental tools will be ultrafast, broadband extreme ultraviolet (XUV) spectroscopy and resonant small angle scattering to capture a microscopic picture of the element-specific magnetization dynamics on the femtosecond time and nanometer length scale. These will be complemented by all-optical Kerr spectroscopy and microscopy.

Publications (1^st Funding Period 2018 - 2021)

• Sub-15-fs X-ray pump and X-ray probe experiment for the study of ultrafast magnetization dynamics in ferromagnetic alloys 
  X. Liu, A. Merhe, E. Jal, R. Delaunay, R. Jarrier, V. Chardonnet, M. Hennes, S. G. Chiuzbaian, K. Légaré, M. Hennecke, I. Radu, C. von Korff Schmising, S. Grunewald, M. Kuhlmann, J. Lüning, and B. Vodungbo 
  Opt. Express 29, 32388 (2021)  - DOI: 10.1364/OE.430828

• Laser-driven resonant magnetic soft-x-ray scattering for probing ultrafast antiferromagnetic and structural dynamics 
  D. Schick, M. Borchert, J. Braenzel, H. Stiel, J. Tümmler, D. E. Bürgler, A. Firsov, C. von Korff Schmising, B. Pfau, and S. Eisebitt  
  Optica 8, 1237 (2021)  - DOI: 10.1364/OPTICA.435522

• Wide-field magneto-optical microscope to access quantitative magnetization dynamics with femtosecond temporal and sub-micrometer spatial resolution 
  F. Steinbach, D. Schick, C. von Korff Schmising, K. Yao, M. Borchert, W. D. Engel, and S. Eisebitt 
  J. Appl. Phys. 130, 083905 (2021)  - DOI: 10.1063/5.0060091

• Angular momentum redistribution in laser-induced demagnetization 
  J. K. Dewhurst, S. Shallcross, P. Elliott, S. Eisebitt, C. v. Korff Schmising, and S. Sharma 
  Phys. Rev. B 104, 054438 (2021)  - DOI: 10.1103/PhysRevB.104.054438

• High-speed spatial encoding of modulated pump-probe signals with slow area detectors 
  D. Schick, F. Steinbach, T. Noll, C. Strüber, D. Engel, C. von Korff Schmising, B. Pfau, and S. Eisebitt  
  Meas. Sci. Technol. 32, 025901 (2021)  - DOI: 10.1088/1361-6501/abbc89

• Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co₈₈Tb₁₂ thin film with stripe domains 
  M. Hennes, A. Merhe, X. Liu, D. Weder, C. von Korff Schmising, M. Schneider, C. M. Günther, B. Mahieu, G. Malinowski, M. Hehn, D. Lacour, F. Capotondi, E. Pedersoli, I. P. Nikolov, V. Chardonnet, E. Jal, J. Lüning, and B. Vodungbo 
  Phys. Rev. B 102, 174437 (2020)  - DOI: 10.1103/PhysRevB.102.17443

• Element-specific magnetization dynamics of complex magnetic systems probed by ultrafast magneto-optical spectroscopy 
  C. von Korff Schmising, F. Willems, S. Sharma, K. Yao, M. Borchert, M. Hennecke, D. Schick, I. Radu, C. Strüber, D. W. Engel, V. Shokeen, J. Buck, K. Bagschik, J. Viefhaus, G. Hartmann, B. Manschwetus, S. Grunewald, S. Düsterer, E. Jal, B. Vodungbo, J. Lüning, and S. Eisebitt 
  Appl. Sci. 10, 7580 (2020)  - DOI: 10.3390/app10217580

• A tabletop setup for ultrafast helicity-dependent and element-specific absorption spectroscopy and scattering in the extreme ultraviolet spectral range 
  K. Yao, F. Willems, C. von Korff Schmising, C. Strüber, P. Hessing, B. Pfau, D. Schick, D. Engel, K. Gerlinger, M. Schneider, and S. Eisebitt 
  Rev. Sci. Instrum. 91, 093001 (2020)  - DOI: 10.1063/5.0013928

• Distinct spectral response in M-edge magnetic circular dichroism 
  K. Yao, F. Willems, C. von Korff Schmising, I. Radu, C. Strüber, D. Schick, D. Engel, A. Tsukamoto, J. K. Dewhurst, S. Sharma, and S. Eisebitt 
  Phys. Rev. B 102, 100405(R)  (2020)  - DOI: 10.1103/PhysRevB.102.100405

• Transient magnetic gratings on the nanometer scale 
  D. Weder, C. von Korff Schmising, C. M. Günther, M. Schneider, D. Engel, P. Hessing, C. Strüber, M. Weigand, B. Vodungbo, E. Jal, X. Liu, A. Merhe, E. Pedersoli, F. Capotondi, J. Lüning, B. Pfau, and S. Eisebitt 
  Struct. Dyn. 7, 054501 (2020)  - DOI: 10.1063/4.0000017

• Element specificity of transient extreme ultraviolet magnetic dichroism 
  J. K. Dewhurst, F. Willems, P. Elliott, Q. Z. Li, C. von Korff Schmising, C. Strüber, D. W. Engel, S. Eisebitt, and S. Sharma
  Phys. Rev. Lett. 124, 077203 (2020)  - DOI: 10.1103/PhysRevLett.124.077203

• Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy
  F. Willems, C. v. Korff Schmising, C. Strüber, D. Schick, D. W. Engel, J. K. Dewhurst, P. Elliott, S. Sharma, and S. Eisebitt 
  Nat. Commun. 11: 871 (2020)  - DOI: 10.1038/s41467-020-14691-5

• Magneto-optical functions at the 3p resonances of Fe, Co, and Ni: Ab initio description and experiment
  F. Willems, S. Sharma, C. v. Korff Schmising, J. K. Dewhurst, L. Salemi, D. Schick, P. Hessing, C. Strüber, W. D. Engel, and S. Eisebitt
  Phys. Rev. Lett. 122, 217202 (2019) - DOI: 10.1103/PhysRevLett.122.217202