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TT: Fachverband Tiefe Temperaturen

TT 58: Multiferroics II (organized by MA)

TT 58.10: Vortrag

Mittwoch, 2. April 2014, 12:00–12:15, HSZ 04

Structure and Magnetic Coupling in YBaFeCuO₅ — •Andrea Scaramucci¹, Mickael Morin², Ekaterina Pomjakushina², Marek Bartkowiak², Denis Sheptyakov², Lukas Keller², Juan Rodriguez-Carvajal³, Michel Kenzelmann², Kazimierz Conder², Marisa Medarde², and Nicola A. Spaldin¹ — ¹Materials Theory, ETH-Zurich, Zurich, Switzerland — ²Paul Scherrer Institute, Villigen, Switzerland — ³Institute Laue Langevin, Grenoble, France

We theoretically study the structure and exchange couplings in multiferroic YBaFeCuO₅ (YBFCO). Using density functional theory we calculate energies of configurations with various Fe³⁺/Cu²⁺ orderings in the bilayered perovskite structure of YBFCO. We find that configurations with different distribution of Fe³⁺ and Cu²⁺ ions fall into two groups with distinctly different energies. The energies of those in the lowest energy group are close to that of the ground state (relative to the growth temperature) suggesting Fe³⁺ and Cu²⁺ to be disordered in YBFCO. Finally, we calculate exchange coupling constants for all the low energy configurations and show that the magnetic ordering resulting from these couplings is compatible with the experimentally-observed high-temperature magnetic ordering. However, they do not explain the existence of the experimentally observed low-temperature incommensurate magnetic structure.