| 研究課題/領域番号 |
18K13489
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| 研究機関 | 東北大学 |
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研究代表者 |
HUYNH KHUONG 東北大学, 材料科学高等研究所, 助教 (60734340)
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| 研究期間 (年度) |
2018-04-01 – 2022-03-31
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| キーワード | PT symmetry / Magnetotransport / Magnetoresistance / Antiferromagnet |
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| 研究実績の概要 |
The main achievement up to now is the observation a novel magnetoresistance in the BaMn2Pn2 antiferromagnets (Pn = As, Sb, Bi) with parity-time symmetry. The resistivities of these materials are reduced by 60 times in magnetic fields, thus yielding a very large magnetoresisance of about -98%. The magnetoresistance changes systematically along with the Pn elements, hinting that its origin is the spin-orbit coupling and/or d-p orbital hybridization. The large magnetoresistance in BaMn2Pn2 exhibits an unique anisotropy under rotating magnetic fields. The large magnitude and the unusual anisotropy indicate a new kind of large magnetoresistance that has not been encountered so far in any other material. Our findings call for a new mechanism of the magnetoresistance in parity-time symmetric antiferromagnets. The paper reporting the data is now in press.
In the course of making the main achievement described above, we have successfully grown high quality single crystals of BaMn2Pn2. In order to measure electrical transport properties under high magnetic fields, we constructed a new measurement probe equipped with a rotator. This probe can later be employed for other measurements in this project, such as second harmonic measurement or strain-induced current.
We are also making collaborations with other research groups for other measurements, such as nuclear magnetic resonance or angle-resolved photoemission spectroscopy. In particular, the measurements of nuclear magnetic resonance already gave interesting results and a paper is being prepared.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
We ourselves made a lot of efforts in growing single crystals, constructing measurement systems, and writing papers. We successfully synthesized high quality single crystals of antiferromagnets (Pn = As, Sb, Bi).
Using single crystals, we were able to measure the magnetotransport properties under high magnetic fields thanks to the invaluable supports and collaborations at the High Field Laboratory for Superconducting Materials, Institute for Materials Research and Center for Advanced High Magnetic Field Science, Osaka University.
On the other hand, the physical mechanism of the magnetoresistance is still unclear. BaMn2Pn2 are complex systems and the large magnetoresistance are unprecedented. We will address this issue by collaborating with theorist as well as making band calculations.
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| 今後の研究の推進方策 |
We will continue this study focusing on two main directions as follows.
1. New materials by potassium doping. The parity-time symmetry in BaMn2Pn2 is realized via special spin-dependent orbital hybridized states located at the top of the valence band. By partially substituting barium by potassium, we can shift the chemical potential downwards, and therefore we can probe the effects of the parity-time symmetry on the physical properties of the systems.
2. New measurements. We are constructing systems for measuring the second harmonic resistance and strain induced current. According to theoretical predictions, these properties are expected in parity-time symmetric antiferromagnets, and it will be interesting to observe these effects.
We are also collaborating with other researchers to measure the electronic structure and nuclear magnetic resonance of BaMn2Pn2. We will collaborate with theoretical physicist in order to elucidate the mechanism of the large magnetoresistance.
At the time being, the first paper resulting from this study is now in press. We are preparing several papers for publishing our findings.
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