Seminar by Henrik Jacobsen

Henrik Jacobsen

Niels Bohr Institutet

Metal-insulator transitions in correlated antiferromagnets

The double perovskite Pb2CaOsO6 undergoes a transition from showing metallic conductivity at high temperatures, to being insulating at low temperatures. This metal-insulator transition happens simultaneously with the onset of antiferromagnetic order, suggesting that the transition is spin-driven, and could be a rare example of a so-called Slater transition.

In this talk, I will present our work on understanding the metal-insulator transition in Pb2CaOsO6. The journey begins with neutron- and x-ray diffraction to determine the structure of the material. This ultimately leads to the discovery that Pb2CaOsO6 displays antiferroelectric distortions; a rarity in metals. The journey continues with neutron diffraction and muon spin rotation to determine the magnetic structure, and concludes with resonant inelastic scattering to help understand the electronic structure.

At the end of my talk, I will change gears and present the project that brought me back to Copenhagen: Quite recently, the Mn3X (X=Ge, Sn,…) family of materials was shown to have a large anomalous Hall Effect at room temperature. This effect is tied to the magnetic structure of the materials, and I will show how we determined this structure using neutron polarimetry. Finally, I will outline the future work on this project.

I aim to make the talk accessible to people without knowledge of the experimental techniques.