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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 8: Multiferroics and magnetoelectrics I (joint session MA/KFM)

KFM 8.6: Talk

Tuesday, March 13, 2018, 11:00–11:15, EB 202

Soft modes in Ca₃Mn₂O₇ - Direct observation of the order parameters in a hybrid improper ferroelectric material — •Dirk Wulferding^1,2, Alexander Glamazda^3,1, Peter Lemmens^1,2, Bin Gao⁴, Sang-Wook Cheong⁴, and Kwang-Yong Choi⁵ — ¹IPKM, TU-BS, Braunschweig, Germany — ²LENA, TU-BS, Braunschweig, Germany — ³ILTPE, NASU, Kharkov, Ukraine — ⁴Rutgers Univ., New Jersey, USA — ⁵Chung-Ang Univ., Seoul, Korea

In hybrid improper ferroelectric materials the order parameter is still under debate, but predicted to be a combination of rotation and tilting modes. In the title compound Ca₃Mn₂O₇ we observe anomalous softening of rotation and tilting phonons through the transition from the ferroelectric to the paraelectric phase. This clearly underlines their role as order parameters. In addition, a coupling of the soft mode to the magnetic and the electronic subsystems is characterized through an observation of anomalous magnetic and multiphonon Raman scattering. Work supported by the Quantum- and Nanometrology initiative "QUANOMET" within project NL-4, DFG-RTG 1952/1 "NanoMet", Korea NRF Grants (No. 2009-0093817, 2012-046138), and the NSF MRI Grant No. MRI-1532006.