The University of Tokyo · Materials Science
Professor Takeshi Hayashida's research lab specializes in the physics of emergent quantum materials, with a focus on novel ferroic orders such as ferroaxiality, chirality, and magnetoelectricity in complex oxides. The lab employs advanced optical techniques—particularly electrogyration and nonreciprocal optical effects—to experimentally probe and manipulate hidden order parameters that are otherwise difficult to access. A central theme is the development of new methods to visualize and control nanoscale domain structures in materials with broken symmetries, including antiferromagnets and chiral crystals.
Figures are computed from collected data and may differ slightly.
Ferroaxial materials that exhibit spontaneous ordering of a rotational structural distortion with an axial vector symmetry have gained growing interest, motivated by recent extensive studies on ferroic materials. As in conventional ferroics (e.g., ferroelectrics and ferromagnetics), domain states will be present in the ferroaxial materials. However, the observation of ferroaxial domains is non-trivial due to the nature of the order parameter, which is invariant under both time-reversal and space
The ferroaxial order, which is characterized by a rotational structural distortion in a crystal, has been recently proposed as one of ferroic orders. Though the domain formation is a characteristic feature in ferroic materials, there has been little study done concerning that for the ferroaxial order. Here, we investigate ferroaxial domains that are formed through a ferroaxial transition in two representative ferroaxial materials, ${\mathrm{NiTiO}}_{3}$ and $\mathrm{RbFe}{(\mathrm{Mo}{\mathrm{O}
The archetypal magnetoelectric (ME) antiferromagnet ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, which has the diagonal components of linear ME tensor, exhibits several different types of nonreciprocal optical effects: the electric field-induced $(E\text{\ensuremath{-}}\mathrm{induced})$ Faraday effect, the electric field-induced magnetic circular dichroism ($E\text{\ensuremath{-}}\mathrm{induced}$ MCD), and the spontaneous nonreciprocal rotation of reflected light (NRR). In principle, antiferromagnetic
In a chiral medium, any mirror symmetries are broken, which induces unique physical properties represented by natural optical rotation. When electromagnetic waves propagate through a chiral medium placed in a magnetic field, the refractive index, or equivalently, the absorption encountered by the electromagnetic waves differs depending on whether it travels parallel or antiparallel to the magnetic field. Such a phenomenon is known as magnetochiral dichroism (MChD), which is the characteristic in
Antiferromagnets with broken time-reversal ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>T</mml:mi> <mml:annotation>$\mathcal{T}$</mml:annotation></mml:semantics> </mml:math> ) symmetry ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>T</mml:mi> <mml:annotation>$\mathcal{T}$</mml:annotation></mml:semantics> </mml:math> -odd antiferromagnets) have gained extensive attention, mainly due to their ferromagnet-like behavior despite
Switching crystallographic chirality is nontrivial because there is no simple conjugate field to chirality. Here we demonstrate chirality switching in an inorganic crystalline material by manipulating the boundaries of chiral domains with laser irradiation. Our study material is Ba(TiO)Cu<sub>4</sub>(PO<sub>4</sub>)<sub>4</sub>, exhibiting a chiral structure at room temperature and a chiral-achiral phase transition at 710 °C. By irradiation of a laser beam with a wavelength at which Ba(TiO)Cu<su
Ferrotoroidic order refers to a spontaneous vortex arrangement of magnetic dipoles, which has recently been established as the fourth primary ferroic state of matter. Thus far, ferrotoroidic order has been studied extensively in insulators, but much less investigated in metallic materials. Here, the authors demonstrate the visualization of ferrotoroidic domains in metallic NdB${}_{4}$ by spatial distribution measurements of optical second harmonic generation (SHG). This study will stimulate rese
Antiferromagnets with broken time-reversal (T) symmetry (T-odd antiferromagnets) have gained extensive attention, mainly due to their ferromagnet-like behavior despite the absence of net magnetization. However, certain types of T-odd antiferromagnets remain inaccessible by the typical ferromagnet-like phenomena (e.g., anomalous Hall effect). One such system is characterized by a T-odd scalar quantity, the magnetic toroidal monopole. To access the broken T symmetry in such a system, we employ a u
Hematite (alpha-Fe2O3) is a prototypical room temperature antiferromagnet whose time-reversal-odd magnetic structure has recently attracted renewed attention. While such magnetic symmetry can be characterized in terms of higher-order multipoles beyond the magnetic dipole, their manifestation in measurable physical phenomena has remained largely elusive. In this work, we investigate x-ray absorption near the Fe K-edge of hematite under an applied electric field, which explicitly breaks space-inve
Hematite (alpha-Fe2O3) is a prototypical room temperature antiferromagnet whose time-reversal-odd magnetic structure has recently attracted renewed attention. While such magnetic symmetry can be characterized in terms of higher-order multipoles beyond the magnetic dipole, their manifestation in measurable physical phenomena has remained largely elusive. In this work, we investigate x-ray absorption near the Fe K-edge of hematite under an applied electric field, which explicitly breaks space-inve
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Rare-earth orthoferrites (RFeO3, R: rare-earth ions) have long been studied for their unique antiferromagnetic properties arising from the interplay between two magnetic sublattices, formed by Fe³⁺ and R³⁺ ions. From a modern perspective, the antiferromagnetic order in RFeO₃ can be classified as altermagnetic, characterized by macroscopic time-reversal symmetry breaking without net magnetization. In this study, we focus on the altermagnetic Γ₁ phase of DyFeO₃, which exhibits time-reversal symmet
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract The linear electrogyration effect refers to optical rotation induced in proportion to an applied electric field. In comparison with other optical phenomena related to optical rotation, such as natural optical activity and the Faraday effect, the linear electrogyration effect is much less investigated because of the small magnitude of the electric field‐induced rotation. In this study, a microscopic mechanism of the linear electrogyration effect is discussed and it is demonstrated that t
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