Regensburg 2016 – scientific programme

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MA: Fachverband Magnetismus

MA 17: Poster Session I

MA 17.48: Poster

Tuesday, March 8, 2016, 09:30–12:30, Poster B1

Temperature and magnetic field dependent Raman spectroscopy on thin (La_0.65Pr_0.45) _0.7Ca_0.3MnO₃ films — •Sebastian Merten¹, Oleg Shapoval², Bernd Damaschke¹, Konrad Samwer¹, and Vasily Moshnyaga¹ — ¹I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany — ²IIEN, Academy of Science of Republic Moldova, Academia 3/3, MD-2028 Chinisau, Republic of Moldova

Mixed-valence manganites are still in the focus of fundamental research due to their rich phase diagram and intriguing phenomena like the colossal magnetoresistance (CMR). Crucial for understanding the physics of the manganites is the strong electron-phonon coupling manifested as the Jahn-Teller (JT) effect. To study the strong coupling between electrons and phonons, we performed Raman spectroscopy on (La_0.65Pr_0.45) _0.7Ca_0.3MnO₃ thin films (λ = 532 nm, P = 2.9 mW) as a function of temperature and applied magnetic field. We observed four pronounced modes at 235 cm⁻¹, 434 cm⁻¹, 485 cm⁻¹ and 609 cm⁻¹ where the last two arise from the JT effect. The temperature as well as magnetic field dependent Raman spectra show a disorder-order transition observable as an abrupt intensity decrease of the JT modes and a strong increase of the phonon mode at 434 cm⁻¹. This behaviour correlates well with the metal-insulator transition and the CMR effect thus demonstrating a strong change of the electron-phonon coupling at the phase transition and its importance for the CMR effect. Financial support from SFB 1073 (TP B04) is acknowledged.