Celoústavní seminář: A tale of three atoms shaping up ferroelectric, ferrimagnetic and altermagnetic order

In this seminar, I will discuss a scientific journey with just three atoms: Germanium, Manganese and Tellurium. By doping the simplest room-temperature ferroelectric, GeTe, with Manganese, the system develops multiferroic exchange interactions with the competing ferromagnetic, antiferromagnetic and antisymmetric exchange, also known as the Dzyaloshinskii–Moriya interaction, thereby combining magnetism with large topological magnetic vortices emerging from a spin-glass state [1-3]. By fully substituting Germanium with Manganese atoms, the MnTe “magic” near room-temperature antiferromagnet appears, which we recently addressed in the context of altermagnetism – as a central topic of condensed-matter physics demonstrating lifted Kramers spin degeneracy. Is the altermagnetism proving its place on the magnetic family tree as a 3rd distinct magnetic phase without net magnetization, yet with spin-polarization which combines merits of ferromagnets and antiferromagnets thought to be fundamentally incompatible? The experimental results from spin- and angle resolved photoemission spectroscopy carried out at the Swiss Light Source provide us direct evidence: in contrast to ferromagnets or antiferromagnets, altermagnets have a special arrangement of spins which are absent in magnetic systems known so far [4].

References:
1. J. Krempaský et al., Operando imaging of all-electric spin texture manipulation in ferroelectric and multiferroic Rashba semiconductors, Phys. Rev. X 8, 021067 (2018)
2. J. Krempaský et al., Entanglement and manipulation of the magnetic and spin–orbit order in multiferroic Rashba semiconductors, Nat. Comm. 7, 13071 (2016)
3. J. Krempaský et al., Efficient magnetic switching in a correlated spin glass, Nat. Comm. 14, 6127 (2023)
4. J. Krempaský et al., Altermagnetic lifting of Kramers spin degeneracy, Nature 626, 517-522 (2024)

The colloquium will be held in English.