2022 Fiscal Year Research-status Report
Research of the Free-Carrier-Induced Ferroelectric Metal in Layered Perovskite Oxides
| Project/Area Number |
22K04686
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| Research Institution | Kyoto University |
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Principal Investigator |
YI Wei 京都大学, 工学研究科, 准教授 (50903431)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | Polar metal |
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| Outline of Annual Research Achievements |
Ferroelectric metals combining ferroelectricity and metallicity, two seemingly mutually exclusive properties in one system, strongly stirred the research community. Ferroelectrics with a spontaneous and reversible electric polarization, are promising for a wide range of applications and pose a number of fundamental questions. In general, they are insulators. Introducing itinerant charge carriers is expected to screen the long-range coulomb forces and quench ferroelectricity. This conventional concept was broken when the existence of ferroelectric-like metal was theoretically proposed by Anderson and Blount and the ferroelectric-like structural transition in metallic was experimentally observed in LiOsO3. Although several theoretical predictions of ferroelectric/polar metals have been reported, the experimental observations are still rather rare so far. The core issue of this project is to extend the members of this material family and research the unconventional properties of ferroelectric/polar metal materials.
We have achieved two things in the fiscal year 2022 (FY2022). First, one new metallic transition metal oxide (same to LiOsO3) with ferroelectric-like structural transition at low temperature was successfully synthesized in polycrystalline form. Second, a series of carrier doped layered perovskite oxides with Ruddlesden-Popper type structure was prepared.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In FY2022, we achieved 50% of the final goal of this research project.
One new transition metal oxide with LiNbO3-type structure has been prepared in the polycrystalline form. Its physical properties were examined by a series of characterizations: the polar structure at low temperature was demonstrated by the structure analyses using the synchrotron x-ray diffraction and neutron diffraction data of powder samples; the critical temperature of phase transition was suggested by the anomaly in the curve of specific heat vs temperature, the metallic conductivity was measured at variable temperature.
For the carrier-doped layered perovskite oxides, characterizations of physical properties including electric conductivity in magnetic field at low temperatures suggested the magnetoresistance effect. The possibility of structure phase transition at low temperatures is being examined by the detailed structure analyses of polycrystalline samples using synchrotron x-ray diffraction.
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| Strategy for Future Research Activity |
For the future study in FY2023, we will continue the project and conduct detailed evaluations of physical properties and structures, such as the convergent-beam electron diffraction (CBED) perform to confirm the loss of inversion symmetry. The preparations and structure analyses of ferroelectric/polar metal compounds will be done in doped layered perovskites. We also aim to modulate the functionality of ferroelectric/polar metal materials by the doping carriers.
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| Causes of Carryover |
With the support of this research founding, we have carried out a lot of research work on new materials and acquired some achievements. However, there was a period of stagnant experiments due to the pandemic COVID-19, we had to postpone the purchase of reagents for sample synthesis and optical parts for optical experiments. We will purchase these in FY2023 and carry out the research as proposed.
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| Remarks |
京都大学大学院工学研究科 材料化学専攻 機能材料設計学講座 藤田研究室
http://www1.kuic.kyoto-u.ac.jp
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