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MA: Fachverband Magnetismus

MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)

MA 32.46: Poster

Freitag, 29. Februar 2008, 11:15–14:00, Poster E

Trends in spin exchange interactions and ferroelectric polarization in the orthorhombic RMnO₃ series — Kunihiko Yamauchi¹, Frank Freimuth², Stefan Bluegel², Biplab Sanyal³, Ivan Sergienko⁴, Elbio Dagotto⁴, and •Silvia Picozzi¹ — ¹CNR-INFM, L’Aquila (Italy) — ²IFF, Forschungzentrum Jülich, Germany — ³Uppsala Univ., Sweden — ⁴Oak Ridge Natl. Lab. and Univ. Tennessee, TN (USA)

Recently, magnetic ferroelectricity induced by Heisenberg-type interactions has been theoretically predicted in E-type antiferromagnetic (AFM) HoMnO₃ [1]. In order to fully clarify this unconventional microscopic mechanism, we’ve studied the structural, magnetic and ferroelectric properties for the entire family of orthorhombic RMnO₃ (R= rare earth ions), based on first-principles density functional calculations. The ferromagnetic exchange interaction between nearest-neighbor Mn sites decreases with the ionic radius of R (concomitantly with the in-plane Mn-O-Mn bond angle), whereas the anti-ferromagnetic next-nearest neighbor interaction stays rather constant in the series. The competition of these exchange interactions results in a complicated magnetic phase diagram. The decrease in the Mn-O-Mn angle also affects the hopping integrals between Mn ions (as determined from Wannier functions), so that the calculated electric polarization in E-type AFM RMnO₃ is remarkably reduced throughout the rare earth series.

[1] S. Picozzi et al., Phys. Rev. Lett. (in press).