Berlin 2018 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 25: Ferroics and Multiferroics (joint session KFM/TT/MA)

KFM 25.10: Vortrag

Donnerstag, 15. März 2018, 12:50–13:10, EMH 225

Structural phase transition and domain formation in the hybrid improper ferroelectric Ca₃Mn_1.9Ti_0.1O₇ — •Mads C. Weber¹, Thomas Lottermoser¹, Morgan Trassin¹, Bin Gao², Sang-Wook Cheong², and Manfred Fiebig¹ — ¹ETH Zurich, Switzerland — ²Rutgers University, Piscataway, New Jersey, USA

One of the bottlenecks for the application of magneto-electric multiferroics is the lack of materials with both, a robust coupling between ferroelectricity and magnetism, and a sufficiently large polarization. This problem may be overcome in layered perovskite systems, where octahedral rotations can give rise to improper ferroelectricity as well as a net-magnetization. Accordingly, ferroelectricity and magnetic order are linked by non-polar structural distortions. Essential for the understanding of the potential coupling of both parameters is an in-depth comprehension of the structural distortions and the formation of domains. In this work, we present a combined Raman spectroscopy (RS) and optical second harmonic generation (SHG) study of the improper ferroelectric phase transition and the related domain formation. Using RS, we trace the evolution of the non-polar structural distortions across the phase transition by probing the lattice vibrations of the system. Furthermore, we investigate the emergence of ferroelectricity by SHG a technique highly sensitive to breaking of inversion symmetry. Hence, RS and SHG represent a unique combination to investigate improper ferroelectric phase transitions.