Tsukasa Katayama 교수

Abstract Synthetic techniques to prepare large‐size, flexible, and high‐quality single‐crystalline sheets of transition metal oxides are crucial to developing low‐energy consumption devices. One promising way is a lift‐off and transfer technique using a heterostructure of polymer supporting oxide and Sr 3 Al 2 O 6 (SAO) layers grown on a single‐crystalline substrate. By removing the water‐soluble SAO and the supporting layers, the oxide sheet is obtained. Although some ferroelectric flexible she

SrFeO_3−xF_x epitaxial thin films were obtained from SrFeO_x thin films (<italic>x</italic> ≈ 2, 2.5, and 3) by polyvinylidene fluoride treatment at 150–270 °C.

Abstract GaFeO 3 ‐type iron oxide is a promising room‐temperature multiferroic material due to its large magnetization. To expand its usability, controlling the ferroelectric and magnetic properties is crucial. In this study, high‐quality Ga x Fe 2– x O 3 ( x = 0–1) epitaxial films are fabricated and their properties are systematically investigated. All films exhibit room‐temperature out‐of‐plane ferroelectricity, showing that the coercive electric field ( E c ) decreases monotonically with x .

GaFeO3-type iron oxides are promising multiferroic materials due to the coexistence of a large spontaneous magnetization and polarization near room temperature. However, magnetic substitution, which is a general method to control multiferroic properties, is difficult due to instability of the substituted GaFeO3. In this study, Ga0.5Cr0.5FeO3 epitaxial thin films are successfully fabricated through epitaxial stabilization. These films exhibit in-plane ferrimagnetism and out-of-plane ferroelectric

Coexistence of large magnetization and reversible polarization at room temperature in ε-Fe₂O₃-type iron oxide.

Oxyhydride SrVO2H epitaxial thin films were fabricated on SrTiO3 substrates via topotactic hydridation of oxide SrVO3 films using CaH2. Structural and composition analyses suggested that the SrVO2H film possessed one-dimensionally ordered V-H−-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO2H film was reversible to SrVO3 by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurem

Flexible and functional perovskite oxide sheets with high orientation and crystallization are the next step in the development of next-generation devices. One promising synthesis method is the lift-off and transfer method using a water-soluble sacrificial layer. However, the suppression of cracks during lift-off is a crucial problem that remains unsolved. In this study, we demonstrated that this problem can be solved by depositing amorphous Al₂O₃ capping layers on oxide she

In multiferroic GaFeO3 (GFO)-type iron oxides, spontaneous polarization and magnetization coexist at room temperature along the [001]GFO and [100]GFO directions, respectively. Due to the large magnetocrystalline anisotropy and polarization direction in GFO, controlling the domain configuration and orientation is crucial when designing the ferroelectric and ferrimagnetic properties. In this study, we fabricate Ga0.6Fe1.4O3 epitaxial thin films on various substrates to investigate the substrate ef

The substitution of hydride anions (H−) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained during t

The antiferroelectric (AFE) phase, in which nonpolar and polar states are switchable by an electric field, is a recent discovery in promising multiferroics of hexagonal rare-earth manganites (ferrites), <i>h</i>-<i>R</i>Mn(Fe)O₃. However, this phase has so far only been observed at 60-160 K, which restricts key investigations into the microstructures and magnetoelectric behaviors. Herein, we report the successful expansion of the AFE temperature range (10-300 K) by preparing <i>h</i>-

YBaCo₂O₆ epitaxial thin films with strong ferromagnetic anisotropy were obtained <italic>via</italic> low-temperature topotactic oxidation using a strong oxidizing agent NaClO.

Abstract We investigated the electronic structure of perovskite SrFeO 3− x F x (0.6 ≤ x ≤ 1) films by optical absorption, photoemission, and X-ray absorption spectroscopies, as well as density functional theory (DFT)-based calculations. The optical bandgap expanded with x , yielding a wider direct bandgap for the SrFeO 2 F film than for the LaFeO 3 film. The DFT calculations suggested that the majority of FeO 4 F 2 octahedra in the SrFeO 2 F film had cis configurations and that the enlarged band

Double-perovskite GdBaCo2O5.5 (GBCO) exhibits various fascinating features, including temperature- and magnetic-field-induced ferromagnetic to antiferromagnetic phase transition associated with the two ionic orders: an A-site Gd/Ba order along the c-axis, and an octahedral CoO6/pyramidal CoO5 order along the b-axis. However, the fine control of ionic orders remains a challenging issue. Herein, we demonstrate the engineering of ionic orders in GBCO films through appropriate selection of substrate

The AFE–FE phase transition was demonstrated in h -DyFeO 3 films with the lattice parameter c / a ratio of 1.90–1.92, which is intermediate between those of previously reported AFE and FE h-R FeO 3 .