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The electron-phonon interaction is known as one of the major mechanisms determining electrical and thermal properties. In particular, it alters the carrier transport behaviors and sets fundamental limits to carrier mobility. Establishing how electrons interact with phonons and the resulting impact on the carrier transport property is significant for the development of high-efficiency electronic devices. Here, carrier transport behavior mediated by the electron-phonon coupling in BiFeO3 epitaxial thin films is directly observed. Acoustic phonons are generated by the inverse piezoelectric effect and coupled with photocarriers. Via the electron-phonon coupling, doughnut shape carrier distribution has been observed due to the coupling between hot carriers and phonons. The hot carrier quasi-ballistic transport length can reach 340 nm within 1 ps. The results suggest an effective approach to investigating the effects of electron-phonon interactions with temporal and spatial resolutions, which is of great importance for designing and improving electronic devices.

Acoustically actuated magnetoelectric (ME) antennas based on resonant magnetoelectric coupling within ferromagnetic/piezoelectric ME laminated composites have recently been considered as a promising solution for antenna miniaturization. However, its radiation performance has been theoretically overestimated, since the negative effects on performances due to the magnetization saturation and the nonlinear mechanical behavior that occur from high-field driving have not been paid enough attention. This work presents a unique equivalent-circuit-based numerical method to analyze the near-field resonance radiation performances of ME antennas driven by high electric fields. In this method, we establish an equivalent circuit of the converse magnetoelectric effect for a ME laminated composite to describe the operating principle of acoustically actuated electromagnetic radiation. The equivalent parameters related to resonance characteristics are determined by fitting the circuit model to the data from frequency response measurements of the near-field magnetic flux density. The validity of the model is verified by comparing the theoretical predictions with the experimental results, in the view of the volume fraction dependence of the mechanical resonance-related radiation characteristics of the fabricated ME composites. Based on the proposed model, the influence of driving voltage amplitude on near-field radiation performances is further analyzed by experimental fitting to the model, and the potential limiting factors of ME antennas are discussed according to the driving-amplitude dependence of parameters obtained from the fit. This work provides an effective and engineering-friendly approach to predict the evolution of ME antenna performances, leading a way to improve the performance limit for resonant magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

The micro-discharge effect limits the development of high-frequency microwave power components to miniaturization and integration. Therefore, it has become a focus of research to effectively suppress the micro-discharge effect, increase the micro-discharge threshold, and strengthen the environmental stability of high-frequency microwave devices. In this study, different elemental ratios of carbon (C)/silver (Ag)/titanium (Ti) composite films were obtained by multi-target magnetron co-sputtering technology and then systematically analyzed for micro-discharge effects. When the doping ratio of C/Ag/Ti was 3.538/1/0.013, the corresponding maximum secondary electron emission coefficient (δmax) decreased to 1.01 owing to the suppression of secondary electron emission by the increase in the content of sp2 hybrid bond. The micro-discharge threshold of Ku band waveguide filters coated with moderate C/Ag/Ti composite films showed an optimal performance of 10 000−12 500 W, which was increased by approximately 20 times. Moreover, the microstructure of the composite films exhibited higher density and flatness with a tiny increase in the titanium doping ratio, representing good environmental stability. Thus, the effective suppression of the secondary electron emission yield, significant improvement in the micro-discharge threshold, and enhancement of the environment stability of microwave components could be realized simultaneously by reasonably controlling the content of titanium in silver and titanium co-doped carbon-based composite films. [ABSTRACT FROM AUTHOR]

Controlling magnetization dynamics is imperative for developing ultrafast spintronics and tunable microwave devices. However, the previous research has demonstrated limited electric-field modulation of the effective magnetic damping, a parameter that governs the magnetization dynamics. Here, we propose an approach to manipulate the damping by using the large damping enhancement induced by the two-magnon scattering and a nonlocal spin relaxation process in which spin currents are resonantly transported from antiferromagnetic domains to ferromagnetic matrix in a mixed-phased metallic alloy FeRh. This damping enhancement in FeRh is sensitive to its fraction of antiferromagnetic and ferromagnetic phases, which can be dynamically tuned by electric fields through a strain-mediated magnetoelectric coupling. In a heterostructure of FeRh and piezoelectric PMN-PT, we demonstrated a more than 120% modulation of the effective damping by electric fields during the antiferromagnetic-to-ferromagnetic phase transition. Our results demonstrate an efficient approach to controlling the magnetization dynamics, thus enabling low-power tunable electronics.

Efficient electrical control of magnetic property is critical for the development of various spintronics. However, traditional magnetoelectric devices require adoption of piezoelectric component, resulting in complicated device architecture and complex conditioning circuit. More importantly, traditional strain-mediated magnetoelectric structures could not be developed in flexible form due to the existence of magnetostrictive component, which could be easily affected by mechanical deformation in flexible devices. Here we have systematically investigated pure current control of the magnetic properties of La0.7Sr0.3MnO3 thin films. Ferromagnetic to paramagnetic phase transition has been realized with a small current density of 5.2 × 103 A/cm2, which is three orders smaller than the working current density of spintronics based on spin-orbit torque and spin-transfer torque. The effective tuning of magnetic property has been attributed to the current induced Joule heating effect. For La0.7Sr0.3MnO3 film grown on flexible Mica with a smaller thermal conductivity, dramatic change of ferromagnetic resonance field of 1340 Oe and nonvolatile magnetization switching have been achieved with an ultra-small current density of 7.4 × 102 A/cm2. These results represent a crucial step towards effective electrical control of both static and dynamic magnetic properties in flexible magnetic thin films and open a new avenue for exploring electrical controlled flexible spintronics. [ABSTRACT FROM AUTHOR]

For the application of high-frequency current detection in power systems, such as very fast transient current, lightning current, partial discharge pulse current, etc., current sensors with a quick response are indispensable. Here, we propose a high-frequency magnetoelectric current sensor, which consists of a PZT piezoelectric ceramic and Metglas amorphous alloy. The proposed sensor is designed to work under d15 thickness-shear mode, with the resonant frequency around 1.029 MHz. Furthermore, the proposed sensor is fabricated as a high-frequency magnetoelectric current sensor. A comparative experiment is carried out between the tunnel magnetoresistance sensor and the magnetoelectric sensor, in the aspect of high-frequency current detection up to 3 MHz. Our experimental results demonstrate that the d15 thickness-shear mode magnetoelectric sensor has great potential for high-frequency current detection in smart grids. [ABSTRACT FROM AUTHOR]

Flexible electronics strongly demand the integration of flexible and large‐scale multifunctional oxides. BiFeO3 is one of the most essential multifunctional oxides that could be used in memories, logics, sensors, and actuators. Recently, freestanding single‐crystalline BiFeO3 membranes exhibited superior elasticity and flexibility. However, fabrication and integration of large‐scale freestanding BiFeO3 membranes into flexible electronics remain elusive. In this study, inch‐scale freestanding single‐crystalline BiFeO3 membranes are fabricated with assistance from a water‐soluble sacrificial layer. To transfer flat and crack‐free membranes, all the existing methods are first followed but fail. Then the study introduces a temporary supporting Cu layer on the surface of the as‐grown SiTiO3/Sr3Al2O6/(SrRuO3/)BiFeO3 heterostructure and successfully obtains full and crack‐free 5 mm × 5 mm freestanding membranes on various substrates. The residual strain within the heterostructure releases gradually under the protection of the Cu layer. The freestanding BiFeO3 membranes are relatively uniform among different regions and exhibit good dielectric, ferroelectric, and ferromagnetic properties. Finally, flexible ferroelectric photovoltaic devices are patterned based on those BiFeO3 membranes, and they have open circuit voltage and short circuit current density up to −0.25 ± 0.03 V and 0.82 ± 0.09 µA cm−2, respectively. [ABSTRACT FROM AUTHOR]