Browsing by Author "Zhou, Yichun"

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Characterization of domain distributions by second harmonic generation in ferroelectrics
(2018-07-24)
Zhang, Yuan
;
Zhang, Yi
;
Guo, Quan
;
Zhong, Xiangli
;
Chu, Yinghao
Domain orientations and their volume ratios in ferroelectrics are recognized as a compelling topic recently for domain switching dynamics and domain stability in devices application. Here, an optimized second harmonic generation method has been explored for ferroelectric domain characterization. Combing a unique theoretical model with azimuth-polarization-dependent second harmonic generation response, the complex domain components and their distributions can be rigidly determined in ferroelectric thin films. Using the proposed model, the domain structures of rhombohedral BiFeO3 films with 71 degrees and 109 degrees domain wall, and, tetragonal BiFeO3, Pb( Zr0.2Ti0.8)O-3, and BaTiO3 ferroelectric thin films are analyzed and the corresponding polarization variants are determined. This work could provide a powerful and all-optical method to track and evaluate the evolution of ferroelectric domains in the ferroelectric-based devices.
Discovery of a magnetic conductive interface in PbZr0.2Ti0.8O3 /SrTiO3 heterostructures
(2018-02-15)
Zhang, Yi
;
Xie, Lin
;
Kim, Jeongwoo
;
Stern, Alex
;
Wang, Hui
Emergent physical properties often arise at interfaces of complex oxide heterostructures due to the interplay between various degrees of freedom, especially those with polar dis-continuities. It is desirable to explore if these structures may generate pure and controllable spin currents, which are needed to attain unmatched performance and energy efficiency in the next-generation spintronic devices. Here we report the emergence of a spin-polarized two-dimensional electron gas (SP-2DEG) at the interface of two insulators, SrTiO3 and PbZr0.2Ti0.8O3. This SP-2DEG is strongly localized at the interfacial Ti atoms, due to the interplay between Coulomb interaction and band bending, and can be tuned by the ferroelectric polarization. Our findings open a door for engineering ferroelectric/insulator interfaces to create tunable ferroic orders for magnetoelectric device applications and provide opportunities for designing multiferroic materials in heterostructures.