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Disputation Ivar Kumberg

11.11.2022 | 17:00
Thema der Dissertation:
Ultrafast demagnetization in metallic ferromagnetic / antiferromagnetic heterostructures
Abstract: This thesis summarizes experimental work performed on thin-film metallic and magnetic systems by time-resolved soft X-ray reflectivity and magneto-optical Kerr effect measurements.
The delay-time-dependent magnetization dynamics in Co, Mn, and Ni after laser excitation are investigated in layered systems. The work aims to study the effects of antiferromagnetic coupling on de- and remagnetization dynamics in an adjacent ferromagnetic film on the ultrafast timescale. The presented work bridges the timescale from the first femtoseconds to macroscopic dynamics after several microseconds. In the talk, two studies performed within this project are presented.
First, differences between the ultrafast demagnetization in a Cu/Co/NiMn/Cu(001) system recorded at high and low sample base temperatures are discussed. The report shows that the antiferromagnetic alignment in the NiMn system, present at low temperatures, facilitates a faster demagnetization of the adjacent Co layer compared to a magnetically disordered NiMn layer at high temperatures.
The second investigation presented in the talk covers the timescale of laser excitation and shows experimental evidence of the optically induced intersite spin transfer in a (Co/Mn)x6/Cu(001) multilayer system. An increase in the magnetic contrast in the antiferromagnetically ordered Mn layer is observed. The magnetic contrast lives for the time of excitation and indicates a realignment of the magnetic moments of the interface layers of Mn in the direction of Co.

Zeit & Ort

11.11.2022 | 17:00

Hörsaal B (0.1.01)
Fachbereich Physik, Arnimallee 14, 14195 Berlin