Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Electron Theory
MA 30.11: Vortrag
Donnerstag, 28. Februar 2008, 17:15–17:30, H 1028
Collapse of strong ferromagnetism in YCo5 under pressure - a magnetically driven electronic topological transition evidenced by XMCD — •Helge Rosner1, Angela Trapananti2, Miriam Schmitt1, Ulrich Schwarz1, and Manuel Richter3 — 1MPI CPfS Dresden, Nöthnitzer Straße 40, 01187 Dresden — 2ESRF, BP220, 38043 Grenoble, France — 3IFW Dresden , PF 270116, 01171 Dresden
Isomorphic lattice collapse under pressure is a rare phenomenon, usually related to a change of chemical valence. The most famous examples are SmS and Ce metal, collapsing isomorphically under pressure with about 15% volume reduction. In SmS the electronic transition is ascribed to a change of valence, in Ce it is connected with altering contributions of the 4f-electrons to the chemical bonding. In contrast, the investigated YCo5 obviously is a compound with a stable valence. An entirely new type of isomorphic electronic transition under hydrostatic pressure has been reported recently using ab-initio electronic structure calculation and high-pressure x-ray diffraction.[1,2] The volume collapse is characterized as a first-order Lifshitz or electronic topological transition (ETT) and assigned to magnetic exchange interactions. This mechanism is now directly evidenced by a combination of high pressure XMCD measurements and DFT band structure calculations, both revealing a substantial drop of the magnetic moment related to the phase transition.
[1] H. Rosner et al., Nature Physics 2, 469, (2006).
[2] D. Koudela et al., Phys. Rev. B. (submitted)