We experimentally study a strain-meditated converse magnetoelectric (CME) effect in multiferroic heterostructures consisting of Co 2 MnSi and Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT). To investigate ...the CME effect, Co 2 MnSi films are grown on PMN-PT(001) at various growth temperatures by molecular beam epitaxy. Using magneto-optical Kerr-effect and strain measurements, we find that the remanent magnetization state only for the <inline-formula> <tex-math notation="LaTeX">L 2_{1} </tex-math></inline-formula>-ordered Co 2 MnSi/PMN-PT is modulated by the application of the lattice strain, while that for the <inline-formula> <tex-math notation="LaTeX">B2 </tex-math></inline-formula>-ordered Co 2 MnSi/PMN-PT is insensitive to the strain. We conclude that the formation of <inline-formula> <tex-math notation="LaTeX">L 2_{1} </tex-math></inline-formula>-ordered structure is needed to obtain an effective CME effect in the Co 2 MnSi/PMN-PT multiferroic heterostructure.
We find relatively large inverse local two-terminal magnetoresistance (MR) effect in ferromagnet (FM)/semiconductor (SC) lateral spin-valve devices. The local MR as a function of the bias voltage ...applied between two FM/SC contacts shows nonlinear variation, including sign inversion in high bias-voltage conditions. The inverse local MR can be observed up to room temperature, while conventional positive local MR disappears at around 225 K. To consider the origin of the large inverse MR effect, the influence of the nonlinear spin-detection efficiency at a biased FM/SC contact and the spin-drift effect in the SC channel are discussed.
Energy state and coordination of fluorine (F)-passivated Ge surface have been theoretically analyzed by
semi-empirical molecular orbital method in comparison with hydrogen-passivated Ge surface to ...predict usefulness of F for passivation element and surface stabilization. Heat of formation for the reaction of F atoms and Ge layer system decreased simultaneously without energy barrier. Resultantly, F–Ge bonds were formed on Ge layer system and Ge surface dangling bonds were passivated by F dissimilar to the reaction of H atoms and Ge layer system. Furthermore, it was confirmed experimentally that the electrical properties of HfO
2/Ge gate stack were improved by F
2-ambient treatment of Ge substrate prior to HfO
2 deposition. It is concluded that F-passivation of Ge surface is useful in making stable and low-defective Ge substrate for high-
k dielectric layer deposition.
The vibration amplitude, damping ratio and viscous damping force in capacitive micromachinedultrasonic transducers (CMUTs) with a perforated membrane have been calculated theoretically and compared ...with the experimental data on its vibration behavior. The electrical bias of the DC and the AC voltages and the operation frequency conditions influence the damping effect because leads to variations in the gap height and the vibration velocity of the membrane. We propose a new estimation method to determine the damping ratio by the decay rate of the vibration amplitudes of the perforated membrane plate are measured using a laser vibrometer at each frequency, and the damping ratios were calculated from those results. The influences of the vibration frequency and the electrostatic force on the damping effect under the various operation conditions have been studied.
Capacitive micromachined ultrasonic transducers (CMUTs) with a perforated membrane have been fabricated and characterized in air. Two types of CMUT device have been fabricated having perforation ...ratio (area ratio of holes
=
AR) of 10% and 20%, and analyzed about electrical and mechanical characteristics. The perforation ratio (AR) of membrane substantially influences on the electrostatic force and mechanical restoring force of the device since it leads to the area variation of electrode and membrane, it subsequently influences on the sensitivity and frequency response of the CMUT device. The electrostatic force and mechanical restoring force were improved by decreasing the AR and increasing the DC bias voltage. The open-circuit sensitivity of a CMUT having AR 10% membrane, 8.45
μV/Pa, is larger than that of AR 20%, 4.07
μV/Pa at DC 15
V. Furthermore, the resonance behaviors were observed in the range of 60–80
kHz, and the resonance frequency could be changed by varying the applied DC voltage and AR.
BiFe₁ ₋ₓZnₓO₃ (BFZO) thin films (x = 0, 0.05, and 0.1) have been prepared on Pt/TiO₂/SiO₂/Si substrate by pulsed laser deposition and their multiferoic properties have been investigated. BFZO thin ...films shows polycrystalline perovskite single phase. The grains become small with increasing the substitution of Zn, and leakage current of BFZO thin film for x = 0.05 was lower than that of BiFeO₃ thin film. The dielectric constant of BFZO thin films for x = 0, 0.05, and 0.1 are 107, 146, and 170 at room temperature, respectively. P-E hysteresis loops were obtained at room temperature and 80 K, and Pᵣ slightly increases at low frequency from 500 Hz to 20 kHz. M-H hysteresis loops show weak ferromagnetic properties at 300 K and 80 K by substitution of Zn.
Epitaxial BiFeO
3
(BFO) thin films have been prepared on La-doped (001) SrTiO
3
substrates (La-STO) by using magnetic-field-assisted pulsed laser deposition. X-ray diffraction patterns of the ...epitaxial BFO thin films prepared under magnetic fields of 0, 0.1, and 0.4 T show only (00ℓ) diffraction peaks without secondary phases. From the results of reciprocal space mapping for all epitaxial BFO thin films, (003) reflections show splitting spots, and asymmetric spots of (−103) and (103) reflections exhibit a rhombohedral structure. The microstructure of the epitaxial thin films was modified by the strength of magnetic field, and a columnar structure was shown in the film prepared under a high deposition rate for a magnetic field of 0.4 T. The polarization versus electric field hysteresis loops were obtained at room temperature (RT) in all the epitaxial films; in particular, the remanent polarization for the epitaxial film prepared under a magnetic field of 0.1 T was 46 µC/cm
2
at RT while the current density was reduced in comparison with those of other epitaxial films.
A multimodal sensor with Si micro-cantilever embedded in PDMS elastomer for measurement of proximity and touch forces has been fabricated and characterized. DC resistance of the strain gauge on the ...cantilever changes in proportion to the indentation depth of the object. On the other hand, the AC (> 0.5 MHz) impedance including photo-sensitive component of Si increases with increase of distance between the sensor surface and the object because of decrease of light intensity reflected on the object surface. Moreover, the AC impedance is different between grounding and floating of the proximate object because of difference of distribution of electrostatic field between electrodes, so that it is suggested that proximity can be detected as the impedance change by light as well as the electric field.
We report on deposition of epitaxial BiFeO₃ (BFO) thin films on SrRuO₃-buffered SrTiO₃ (001) substrate by using ion beam sputtering process. An X-ray diffraction analysis indicate that the BFO thin ...film deposited at 500 °C using a target with Bi/Fe ratio of 1.05 is perovskite single phase and is epitaxially grown on the substrate. The BFO thin film show saturated D-E hysteresis loops and the double remanent polarization (2Pᵣ) of 100 μC/cm² without measurement frequency dependence.
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