Regensburg 2025 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 1: (Multi)ferroic States: From Fundamentals to Applications (I)

KFM 1.2: Vortrag

Montag, 17. März 2025, 10:00–10:15, H9

Tailoring ferroelectric to antipolar phase interconversion in multiferroic thin films — •Bixin Yan¹, Marvin Müller¹, Hyeon Ko¹, Yen-Lin Huang^2,3,4, Haidong Lu⁵, Alexei Gruverman⁵, Ramamoorthy Ramesh^3,4,6, Marta D. Rossell⁷, Manfred Fiebig¹, and Morgan Trassin¹ — ¹ETH Zurich, Switzerland — ²National Yang Ming Chiao Tung University, Taiwan — ³University of California, Berkeley, USA. — ⁴Lawrence Berkeley Laboratory, USA. — ⁵University of Nebraska-Lincoln, USA — ⁶Rice University, USA. — ⁷Empa, Switzerland.

Inversion-symmetry breaking and the emergence of a polar state are essential for technologically relevant effects such as ferroelectricity and nonlinear optical properties. Hence, the ability to reversibly control the onset of such symmetry breaking can be instrumental in establishing emergent computing schemes. In this work, we present a novel approach for reversible control over the ferroelectric-to-antipolar phase transition in epitaxial multiferroic La-substituted BiFeO₃ (LBFO) thin films using local pressure and electric field. Utilizing local stress application via a scanning-probe-microscopy tip, we stabilize the antipolar phase. An electric field restores the original ferroelectric phase. Leveraging these insights, we establish the continuous tuning of the ferroelectric/antipolar phase coexistence and can set the net polarization of LBFO to any desired value between its saturation limits. Finally, using optical second harmonic generation as a non-invasive probe, we control the net polarization of our films in device-compliant capacitor heterostructures.

Keywords: Ferroelectric oxide; Epitaxial thin film; Pulsed laser deposition; Phase transition; Memristive behavior