Electric properties of the twelve-fold vortex structure in hexagonal manganites
Hongling Lin1, Kunlun Yang1, Lin Lin2
1Laboratory of Solid State Microstructures, Innovation Center of Advanced Microstructures and School of Physics, Nanjing University, Nanjing 210093, People's Republic of China.
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Hexagonal manganites, as a functional ferroelectric (FE) material, receive considerable attention due to their improper ferroelectricity and topological vortex structures. This family exhibits three low-symmetry states accompanied by distinct vortex domain structures. In addition to the FEP63cmand anti-FE (AFE)P-3c1 states accompanied by dual six-fold vortex structures, there is another FEP3c1 state accompanied by a twelve-fold vortex structure. The responses of FE materials to external stimuli, such as external electric fields, are the core ingredients in the physics of FEs and are significant for technological applications. Under external electric fields, the responses of FE materials are determined by special FE domain structures. The electric properties of the FEP63cmand AFEP-3c1 states are very different. However, the electric properties of the FEP3c1 state, which only stabilizes in Ga-substituted In(Mn, Ga)O3, are unclear. The present work studies the electric properties of the FEP3c1 state. The electric-field-driven transition of the FEP3c1 state is found to follow two sequences, i.e. (1) twelve-foldP3c1 → nine-foldP3c1 +P63cm→ three-foldP63cm, and (2) twelve-foldP3c1 → six-foldP3c1 → three-foldP63cm. The variation of average polarization withEfor the FEP3c1 state with the second transition sequence manifests as an unusual triple-hysteresis loop, different from the usual single-hysteresis loop of FE materials. The results are related to the coexistence of the FE and non-FE domain walls in the FEP3c1 state. Furthermore, it is found that the FEP3c1 state at substitution concentration 0.39 exhibits the highest dielectric response. The results advance our understanding of topological vortex structures in hexagonal manganites.
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