Dresden 2017 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

DF: Fachverband Dielektrische Festkörper

DF 9: Poster Session

DF 9.26: Poster

Dienstag, 21. März 2017, 14:00–16:00, P1C

Magnetic correlations in Eu_1−xHo_xMnO₃ (0≤ x ≤ 0.5) probed by Raman spectroscopy — •Sebastian Elsässer¹, Anatoly M. Balbashov², Alexander A. Mukhin³, and Jean Geurts¹ — ¹Exp. Phys. III, University of Würzburg, Germany — ²Prokhorov GPI, Russian Academy of Sciences, Moscow, Russia — ³General Physics Institute of the Russian Academy of Sciences, Moscow, Russia

The perovskite-like rare-earth manganites RMnO₃ are among the most widely studied compounds in multiferroics, where the magnetically induced ferroelectricity of, for example, TbMnO₃, DyMnO₃ is induced via the inverse Dzyaloshinskii - Moriya (DM) interaction. The mixed stoichiometry compounds like Eu_1−xHo_xMnO₃ allow fine-tuning of the competing ferro- and antiferromagnetic interactions to achieve the cycloidal spin order patterns needed for this mechanism. The presence of magnetic Ho³⁺ introduces an additional coupling that leads to a complete flip of the spin cycloid plane for Ho-contents of x>0.35 from the c- to the b-axis (Pnma). Specific Raman-active phonon modes are prime candidates to probe the temperature- and composition dependent developement of magnetic correlations on a quasi-local level via spin-phonon coupling (SPC). Upon cooling, this is observed as a SPC-induced phonon frequency renormalization which reveals magnetic coupling effects even up to ≈ 100 K, despite the much lower Néel Temperature T_N ≈ 45 K. This is interpreted as the formation of locally correlated spin cycloids, oriented with random helicity, which explains the absence of global magnetic order.