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Molecular Physics seminar

Terahertz magnetism: the key role of the lattice

by Dr Stefano Bonetti (Stockholm University)

FA31 ()


Solid state physics textbooks describe magnetization dynamics in ferromagnetic metals (Fe, Co, Ni and their alloys) disregarding the details of the interaction of the spins with the electrons and the lattice. While this assumption is valid for dynamics up to GHz frequencies, recent theoretical and experimental results indicate that in femtosecond dynamics (i.e. at THz frequencies) such interaction cannot be neglected. Of particular interest is the coupling of the spins with the lattice, which could be used to efficiently control magnetic order at ultrafast time scales. In this talk, I will briefly summarize the current state of affairs in ultrafast magnetism and give an overview of two recent experiments in ferromagnetic metals where we observed: (a) the essential role of lattice defects in ultrafast magnetization dynamics triggered by strong THz fields; (b) the observation, using femtosecond x-ray diffraction, of THz acoustic waves generated by 800 nm laser pulses in crystalline iron films. I will conclude the presentation by illustrating current capabilities and future plans of the newly set up broadband THz source at Stockholm University.