General ILL seminar
organised by College 3
Friday, 6 February 2026 at 10h30
Seminar room 110-111, ILL 50, 1st floor
----------------
Zoom link: https://ill.zoom.us/j/98964195699?pwd=vPhNT17CAeoDUr7QX4PjfyPnWsHuMU.1
Password : SeminarC3
“Hyperfine Interactions as a Probe in Solids: The Example of a Multiferroic System: Bismuth Ferrite”
Doru C. Lupascu
Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE)
Faculty of Engineering, University of Duisburg-Essen, Germany
Hyperfine interactions denote the coupling of the wave functions of nuclear states to the electronic shell of the atom. This coupling is a correction term to the energy of a nuclear state and equally so in reverse manner for the electronic shell of the atom.
Like nuclear magnetic resonance or Mössbaer spectroscopy, the nuclear perturbed gamma-gamma-angular correlation spectroscopy (PAC) investigates this energetic modification of the nuclear state. For sufficiently high nuclear spin value, magnetic interactions as well as quadrupole interactions become accessible. The beauty of the method is its highly local character in the crystal lattice. It directly monitors fields at a particular lattice or defect site. Similar is true for molecules.
Bismuth ferrite is a perovskite crystal exhibiting magnetic and electric ordering phenomena. It is antiferromagnetic and a very good ferroelectric. We used several probe atoms that offer suitable nuclear gamma-gamma cascades to understand these two ordering phenomena in the identical crystal and their coupling. Different from the long term belief, we proved that there is no magnetoelectric coupling in this crystal.
The presentation will introduce the measurement method, and the material system and display how it can be used to investigate solids in a very local manner.
--
Hanno Filter (College 3 Secretary)
External visitors may ask for a site access to tellier(at)ill.fr