In-Plane Current Induced Nonlinear Magnetoelectric Effects In Single Crystal Films of Barium Hexaferrite

This report is on the observation and analysis of nonlinear magnetoelectric effects (NLME) for in-plane currents perpendicularly to the hexagonal axis in single crystals and liquid phase epitaxy grown thin films of barium hexaferrite. Measurements involved tuning of ferromagnetic resonance (FMR) at 56-58 GHz in the multidomain and single domain states in the ferrite by applying a current. Data on the shift in the resonance frequency with input electric power was utilized to estimate the variations in the magnetic parameter that showed a linear dependence on the input electric power. The NLME tensor coefficients were determined form the estimated changes in the magnetization and uniaxial anisotropy field. The estimated NLME coefficients for in-plane currents are shown to be much higher than for currents flowing along the hexagonal axis. Although the frequency shift of FMR was higher for the single domain resonance, the multi-domain configuration is preferable for device applications since it eliminates the need for a large bias magnetic field. Thus, multidomain resonance with current in the basal plane is favorable for use in electrically tunable miniature, ferrite microwave signal processing devices requiring low operating power.

Epitaxial growth of CsPbBr3/PbS single-crystal film heterostructures for photodetection

Epitaxial high-crystallization film semiconductor heterostructures has been proved to be an effective method to prepare single-crystal films for different functional devices in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as building blocks for heterostructures. Here, the conformal vapor phase epitaxy of CsPbBr3 on PbS single-crystal films is realized to form the CsPbBr3/PbS heterostructures via a two-step vapor deposition process. The structural characterization reveals that PbS substrates and the epilayer CsPbBr3 have clear relationships: CsPbBr3(110) // PbS(100), CsPbBr3[ ] // PbS[001] and CsPbBr3[001] // PbS[010]. The absorption and photoluminescence (PL) characteristics of CsPbBr3/PbS heterostructures show the broadband light absorption and efficient photogenerated carrier transfer. Photodetectors based on the heterostructures show superior photoresponsivity of 15 A/W, high detectivity of 2.65 × 1011 Jones, fast response speed of 96 ms and obvious rectification behavior. Our study offers a convenient method for establishing the high-quality CsPbBr3/PbS single-crystal film heterostructures and providing an effective way for their application in optoelectronic devices.

Optical Heating Controlled With a Thermoplasmonic Metasurface

We develop a photothermal technology to control optical heating of polymer and liquid crystal films through a refractory titanium nitride (TiN) metasurface. The metasurface represents an array of identical square-shaped TiN nanoantennas on a Si substrate. Upon CW laser illumination, a TiN nanoantenna experiences anomalous Joule heating at a plasmon resonance. A temperature rise provides a unique opportunity for locally probing phase transitions. In the case of heterogeneous PMMA thin films or polymeric blends, a controlled optical heating is needed to probe the glass transition temperature (Tg) of their constituents. Here, we model a controlled thermal response originating from the TiN nanoantenna under CW laser illumination by using FDTD/FEM methods.

Effect of A Limited Amount of D-Sorbitol on Pitch and Mechanical Properties of Cellulose Nanocrystal Films

A cellulose nanocrystal (CNC) suspension can form liquid crystal films with unique self-assembly behaviors. This gives CNC films a special iridescence, which has potential in many aspects, but the brittleness of pure CNC films limits their application. In this work, we propose a simple physical mixing method to obtain CNC film by adding D-sorbitol as a plasticizer. We first found that low D-sorbitol content (less than 6 wt% in CNC/DS composite solution) did not make a significant difference compared with pure CNC films in optical performance and, at the same time, the mechanical properties of the CNC films were improved. The various low contents of D-sorbitol can be well dispersed in CNC aqueous suspension, and the wavelength of the selectively reflected phenomenon is relatively stable and slightly decreased at 5 nm for concentrations from 0 to 6%. This phenomenon is opposite to that generally reported, where the wavelength of the selective reflected phenomenon increases obviously with the increase in plastic content. The pitch of the chiral structure decreased from 406 to 362 nm with an increase in D-sorbitol concentration. When the content of D-sorbitol reached 4%, the tensile strength, elongation at break, and Young modulus increased to 39.9 Mpa, 3.00%, and 2.99 GPa, respectively.