Past colloquia and seminars


A tale of three atoms displaying ferroelectric, ferrimagnetic and altermagnetic order

General public Seminar

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 complex multiferroic exchange interactions with competing ferromagnetic, antiferromagnetic, and antisymmetric exchange, also known as the Dzyaloshinskii–Moriya interaction, thereby combining magnetism with topological properties inherited from Rashba-type spin-splitting in the host GeTe [1-3]. By 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 combine merits of ferromagnets and antiferromagnets thought to be fundamentally incompatible? The experimental results from spin- and angle resolved photoemission spectroscopy, which I briefly introduce along with the Swiss Light Source beam lines where the photoemission experiments were carried out, provide us a direct evidence: in contrast to ferro- or antiferromagnets, altermagnets have a special combination of the arrangement of spins and crystal symmetries with opposite-spin sublattices connected by rotation rather than translation or inversion [4].

1. Juraj Krempaský et al., Operando Imaging of All-Electric Spin Texture Manipulation in Ferroelectric and Multiferroic Rashba Semiconductors, Phys. Rev. X 8, 021067 (2018)
2. Juraj Krempaský et al., Entanglement and manipulation of the magnetic and spin–orbit order in multiferroic Rashba semiconductors, Nat. Comm. 7, 13071 (2016)
3. Juraj Krempaský et al., Efficient magnetic switching in a correlated spin glass, Nat. Comm. 14, 6127 (2023)
4. Juraj Krempaský et al., Altermagnetic lifting of Kramers spin degeneracy, Nature, 626, p. 517–522 (2024)

When? 27.02.2024 15:15
Where? PER 08 2.73
Chemin du Musée 3
1700 Fribourg
speaker Dr. Juraj Krempaský
Center of Photon Science
Paul Scherrer Institut, Villigen PSI
Invited by group Monney
Contact Département de Physique
Prof. Claude Monney
Chemin du Musée 3
1700 Fribourg