Browsing by Author "Huang, Xiaoxi"

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    Phase Transformation Driven by Oxygen Vacancy Redistribution as the Mechanism of Ferroelectric Hf0.5Zr0.5O2 Fatigue
    (Wiley, 2024) Zhang, Zimeng; Craig, Isaac; Zhou, Tao; Holt, Martin; Flores, Raul; Sheridan, Evan; Inzani, Katherine; Huang, Xiaoxi; Nag, Joyeeta; Prasad, Bhagwati; Griffin, Sinéad M.; Ramesh, Ramamoorthy
    As a promising candidate for nonvolatile memory devices, the hafnia-based ferroelectric system has recently been a hot research topic. Although significant progress has been made over the past decade, the endurance problem is still an obstacle to its final application. In perovskite-based ferroelectrics, such as the well-studied Pb[ZrxTi1−x]O3 (PZT) family, polarization fatigue has been discussed within the framework of the interaction of charged defects (such as oxygen vacancies) with the moving domains during the switching process, particularly at the electrode-ferroelectric interface. Armed with this background, a hypothesis is set out to test that a similar mechanism can be in play with the hafnia-based ferroelectrics. The conducting perovskite La-Sr-Mn-O is used as the contact electrode to create La0.67Sr0.33MnO3 / Hf0.5Zr0.5O2 (HZO)/ La0.67Sr0.33MnO3 capacitor structures deposited on SrTiO3-Si substrates. Nanoscale X-ray diffraction is performed on single capacitors, and a structural phase transition from polar o-phase toward non-polar m-phase is demonstrated during the bipolar switching process. The energy landscape of multiphase HZO has been calculated at varying oxygen vacancy concentrations. Based on both theoretical and experimental results, it is found that a polar to non-polar phase transformation caused by oxygen vacancy redistribution during electric cycling is a likely explanation for fatigue in HZO.
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    Spin disorder control of topological spin texture
    (Springer Nature, 2024) Zhang, Hongrui; Shao, Yu-Tsun; Chen, Xiang; Zhang, Binhua; Wang, Tianye; Meng, Fanhao; Xu, Kun; Meisenheimer, Peter; Chen, Xianzhe; Huang, Xiaoxi; Behera, Piush; Husain, Sajid; Zhu, Tiancong; Pan, Hao; Jia, Yanli; Settineri, Nick; Giles-Donovan, Nathan; He, Zehao; Scholl, Andreas; N’Diaye, Alpha; Shafer, Padraic; Raja, Archana; Xu, Changsong; Martin, Lane W.; Crommie, Michael F.; Yao, Jie; Qiu, Ziqiang; Majumdar, Arun; Bellaiche, Laurent; Muller, David A.; Birgeneau, Robert J.; Ramesh, Ramamoorthy; Rice Advanced Materials Institute
    Stabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the order-disorder skyrmion lattices transition. In addition, non-trivial topological solitons, such as skyrmioniums and skyrmion bags, are realized at room temperature. Our work highlights the influence of random spin control of non-trivial topological spin textures.
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    Switching the spin cycloid in BiFeO3 with an electric field
    (Springer Nature, 2024) Meisenheimer, Peter; Moore, Guy; Zhou, Shiyu; Zhang, Hongrui; Huang, Xiaoxi; Husain, Sajid; Chen, Xianzhe; Martin, Lane W.; Persson, Kristin A.; Griffin, Sinéad; Caretta, Lucas; Stevenson, Paul; Ramesh, Ramamoorthy; Rice Advanced Materials Institute
    Bismuth ferrite (BiFeO3) is a multiferroic material that exhibits both ferroelectricity and canted antiferromagnetism at room temperature, making it a unique candidate in the development of electric-field controllable magnetic devices. The magnetic moments in BiFeO3 are arranged into a spin cycloid, resulting in unique magnetic properties which are tied to the ferroelectric order. Previous understanding of this coupling has relied on average, mesoscale measurements. Using nitrogen vacancy-based diamond magnetometry, we observe the magnetic spin cycloid structure of BiFeO3 in real space. This structure is magnetoelectrically coupled through symmetry to the ferroelectric polarization and this relationship is maintained through electric field switching. Through a combination of in-plane and out-of-plane electrical switching, coupled with ab initio studies, we have discovered that the epitaxy from the substrate imposes a magnetoelastic anisotropy on the spin cycloid, which establishes preferred cycloid propagation directions. The energy landscape of the cycloid is shaped by both the ferroelectric degree of freedom and strain-induced anisotropy, restricting the spin spiral propagation vector to changes to specific switching events.