東京大学 · 物理学・天文学
Tomoya Higo教授の研究室は、反強磁性体や格子フラストレーションが強いスピン系を対象とし、磁気秩序と量子スピン系の新規物性の解明を主眼としています。特に、磁化がほとんどないにもかかわらず強い電気的・磁気的応答を示す反強磁性スピンスケールの新規材料（例：Mn₃Sn、Yb基チalcogenidesスピンゲル）の創出と、そのスピン秩序制御技術の開発を進めています。また、スピントロニクス応用に向けた、反強磁性体を用いた磁気メモリやスイッチング素子の実現可能性を追求しています。
Figures are computed from collected data and may differ slightly.
Abstract Control of magnetization direction is essential for the wide application of ferromagnets; it defines the signal size of memory and sensor. However, the magnetization itself causes a dilemma. While its size matters to obtain strong responses upon its reversal, the large magnetization concomitantly suppresses the range of its directional control because of the demagnetizing field. On the other hand, realization of the desired magnetic anisotropy requires careful engineering of crystalline
Objectives: To explore the association between dental erosion and gastro‐oesophageal reflux disease (GORD), we used an animal model of GORD. Materials and Methods: We performed an operation to force gastro‐duodenal contents reflux in male Wistar rats, and examined the teeth in the reflux rats at 15 or 30 weeks postoperatively. Dental erosion was evaluated based on a slightly modified index from a previous report. Estimation of pH was employed in the oesophageal and gastric contents. Results: Mac
Our polycrystalline sample study on the Yb-based chalcogenide spinels $A{\mathrm{Yb}}_{2}{X}_{4}$ ($A=$ Cd, Mg; $X=$ S, Se) has revealed frustrated magnetism due to the antiferromagnetically coupled Heisenberg spin on a pyrochlore lattice. The crystal electric field analysis indicates the Yb ground state has nearly Heisenberg spins with a strong quantum character of the ground doublet. All the materials exhibit an antiferromagnetic order at 1.4--1.8 K, much lower temperatures than the antiferrom
The pyrite-type antiferromagnet NiS2 exhibits a non-coplanar antiferromagnetic (NAF) spin ordering with four spin sublattices in the temperature region between TN1 = 38 K and TN2 = 30 K, and forms a weak ferromagnetic phase below TN2. We have carried out detailed magnetization measurements using high-quality single crystals of NiS2 to reveal magnetic properties associated with the NAF spin structure. Our results obtained in the field cooling sequence under various magnetic fields μ0HFC reveal th
Due to promising functionalities that may dramatically enhance spintronics performance, antiferromagnets are the subject of intensive research for developing the next-generation active elements to replace ferromagnets. In particular, the recent experimental demonstration of tunneling magnetoresistance and electrical switching using chiral antiferromagnets has sparked expectations for the practical integration of antiferromagnetic materials into device architectures. To further develop the techno
The magnetic Weyl semimetallic state in the chiral antiferromagnet Mn3Sn has attracted interest for its potential in memory technology. Despite vanishingly small magnetization, the material exhibits large transverse responses that can be electrically manipulated, similar to ferromagnets. Through deposition on heated Si/SiO2 substrates, we have fabricated polycrystalline Mn3Sn films that have coarse surfaces, the thinner of which have a discontinuous structure comprised of grains with diameters o
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