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Measurement of 3D vector magnetic field is of vital importance for the development of magnetic navigation, biomedical diagnosis, and microimaging. Traditional 3D magnetic sensors require cooperation of multiple sensors on three orthogonal planes, resulting in disadvantages of bulky size and low spatial resolution. Recently proposed spin orbit torque sensor based on ferromagnetic/heavy‐metal heterostructures can detect three magnetic field components individually due to the different symmetries of current‐polarity‐dependent magnetization dynamic. However, the large driving current density and complex driving procedure hinder their practical application, especially in AC magnetic field detection. Herein, 3D magnetic sensors with dramatically reduced driving current density are reported, one fifth of the original value, by exquisite engineering of the magnetic anisotropy in Pt/Co/Ta heterostructures. With further reduced perpendicular magnetic anisotropy, the sensor in the easy‐cone state demonstrates a record‐high sensitivity of 31196 V A−1 T−1. More importantly, the easy‐cone state sensor can work with an ultralow driving current density of 3.8 kA cm−2, which is three orders lower than previous results. Although easy‐cone state sensor can only measure the z‐axis field, highly compact 3D magnetic sensor can be realized by adoption of two anisotropic magnetoresistance sensors, promising great potential application in space‐ and energy‐restricted scenarios. [ABSTRACT FROM AUTHOR]

A magnetic field sensor consisting of a surface acoustic wave (SAW) generator and a cantilever beam with NdFeB permanent magnets are developed. The working principle of this magnetic sensor relies on the center frequency shift of the SAW device under the magnetic field as a consequence of the torque-effect-induced deformation of the cantilever, which changes the stress on the piezoelectric LiNbO3 and the spacing between the interdigital transducers (IDTs). Compared with other magnetic sensors based on acoustic resonance, the performance of our proposed sensor is greatly enhanced due to the structural design by incorporating the magnetic torque effect. High sensitivity of 1277.69 kHz/Oe and a large percentage change in frequency of 5.177% are achieved in this magnetic sensor near a resonant frequency of 848 MHz. The proposed magnetic sensor based on SAW and torque effect exhibits great potential for applications in magnetic field detection. [ABSTRACT FROM AUTHOR]

Piezoelectric devices based on d 36 mode are remarkably stable that depolarization rarely occurs in d 36 face shear mode, because d 36 mode is completely different from d 15 thickness shear mode, where the applied electric field is perpendicular to poling direction and depolarization is ineluctable due to 90° dipole rotation. However, piezoelectric ceramics conventionally possess three piezoelectric coefficients (i.e., d 33 , d 31 , and d 15), while d 36 only exists in single crystals of specific point groups and cut directions. In this work, we propose a method to realize d 36 piezoelectric coefficient in tetragonal piezoelectric ceramics by mechanical and electric domain engineering. This method is successfully applied in bismuth scandium-lead titanate (abbreviated as BS-PT) high-temperature piezoelectric ceramics with a resultant d 36 up to 160 pC/N, which broadens the application of BS-PT ceramics, such as face shear actuator, energy harvester, transducer, etc. We find that domain engineering by transversal electric poling is preferred compared with the transversal mechanical poling, due to the simpler process, higher reliability, and higher resultant d 36 piezoelectric coefficient. By combining the Diffraction-Plane-Transformation (DPT) model with the domain engineering via transversal electric poling, we demonstrate a quantitative domain engineering method for the first time, which could be used for optimizing the piezoelectric properties by precise design of the domain structures in piezoelectric materials. d 36 piezoelectric coefficient in tetragonal piezoelectric ceramics is successfully realized by a quantitative domain engineering, demonstrating a novel method for optimizing the piezoelectric properties via precise design of the domain structures in piezoelectric materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Piezoelectric ceramic (1 - x)Bi(Sc3/4In1/4)O3-xPbTiO3 (BSIPT) (0.45 ≤ x ≤ 0.70) solid solutions near the morphotropic phase boundary (MPB) were developed for high temperature piezoelectric transducer and actuator applications. It was found that the MPB composition of BSIPT ceramics was in the vicinity of x = 0.6, where it had relatively small tolerance factor t = 0.901 resulting in a high TC of 457 °C, and also optimal properties such as the high Pr = 25.4 μC/cm2, &eh;r = 1153, d33 = 201 pC/N, kp = 0.34, and the low Ec = 23.5 kV/cm. Measurements also showed that the depoling temperature was 360 °C, about 200 °C higher than that of commercialized PZT ceramics, which indicated good temperature stability. BSIPT ceramics are promising candidates for high temperature applications. [ABSTRACT FROM AUTHOR]

High temperature depolarization poses a significant challenge to the practical application of piezoelectric/ferroelectric materials. Determining the depolarization temperature (T d) in such materials is crucial for evaluating their performance under high temperature conditions. Here, we propose a method for observing thermal depolarization by examining the 90º domain switching induced strain. Our results show that the differential thermal expansivities of unpoled and poled tetragonal BiScO 3 -PbTiO 3 (BS-PT) piezoelectric ceramic samples can distinguish between thermal expansion strain and 90º domain switching induced strain. The effectiveness of our proposed method is further confirmed by quantitatively analyzing the 90º domain via X-ray diffraction. Compared to the in-situ resonance-antiresonance impedance spectrum, our method allows for more accurate testing of depolarization temperature, demonstrating significant potential for the direct observation of thermal depolarization in piezoelectric/ferroelectric materials. • The depolarization of tetragonal BS-PT ceramic is investigated by thermal expansivity testing. • Ferroelectric-to-paraelectric phase transition occurs over a wide temperature range below Curie temperature. • Differential thermal expansivities can distinguish between thermal expansion strain and 90º domain switching induced strain. • Thermal expansivity testing is more accurate in depolarization temperature determination. [ABSTRACT FROM AUTHOR]

Uranium is well-known to have serious adverse effects on the ecological environment and human health. Bioremediation stands out among many remediation methods owing to its being economically feasible and environmentally friendly. This study reported a great promising strategy for eliminating uranium by Stenotrophomonas sp. CICC 23833 in the aquatic environment. The bacterium demonstrated excellent uranium adsorption capacity (q max = 392.9 mg/g) because of the synergistic effect of surface adsorption and intracellular accumulation. Further analysis revealed that hydroxyl, carboxyl, phosphate groups and proteins of microorganisms were essential in uranium adsorption. Intracellular accumulation was closely related to cellular activity, and the efficiency of uranium processing by the permeabilized bacterial cells was significantly improved. In response to uranium stress, the bacterium was found to release multiple ions in conjunction with uranium adsorption, which facilitates the maintenance of bacterial life activities and the conversion of uranyl to precipitates. These above results indicated that Stenotrophomonas sp. Had great potential application value for the remediation of uranium. [Display omitted] • Stenotrophomonas sp. CICC 23833 exhibits high potential for uranium treatment. • Uranium adsorption by bacteria is closely related to ion release. • Identification of uranium accumulation sites and adsorbed functional substances. • Permeation treatment effectively improves uranium removal from bacteria. [ABSTRACT FROM AUTHOR]

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]

We report the growth of ferroelectric Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 (PLZT) thick films using a poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA)-modified sol–gel process. A per-coating thickness of ≈0.66 μm has been demonstrated using PVP/VA-modified solution, which is more than doubled that of the PLZT films grown by PVP-modified method, and nearly 6 times the per-coating thickness of films prepared by conventional sol–gel process. PLZT thick films grown on LNO/Ni substrates exhibited denser microstructure, higher remanent polarization (11 μC/cm 2 ) and dielectric tunability (45%), lower leakage current density (≈1.2 × 10 −8 A/cm 2 ), and higher breakdown strength (≈1.6 MV/cm) than those for the samples grown on PtSi substrates. These results demonstrated great potential of using PVP/VA-modified sol–gel process for high power film capacitor applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] High quality PLZT film was deposited on Al foil by in-air crystallization process. [•] LaNiO3 buffer layer improved the electrical properties of overlying PLZT films. [•] PLZT/LaNiO3/Al capacitor had low leakage current and fatigue-free behavior. [•] A high energy storage density of ≈20J/cm3 was calculated. [•] Integration of oxide materials with Al foils are useful for embedded devices. [ABSTRACT FROM AUTHOR]

Abstract: Ferroelectric lead lanthanum zirconate titanate (PLZT) films with 8mol% lanthanum and different Zr/Ti ratios (70/30, 65/35, 58/42, 52/48, 45/55, and 40/60) have been grown on platinized silicon substrates by chemical solution deposition. The effects of the Zr/Ti ratios on the dielectric and ferroelectric properties were investigated for high-power energy storage applications. These films exhibited relaxor behavior and slim polarization–electric field hysteresis loops, and the degree of phase transition diffuseness decreased with increasing Ti. The PLZT films with Zr/Ti=52/48 had a high spontaneous polarization of ≈51.2μC/cm2, a low remanent polarization of ≈9.1μC/cm2, and a low coercive electric field of ≈25.9kV/cm, leading to a recoverable energy density of ≈30J/cm3 and a charge–discharge efficiency of ≈78% at room temperature. The high energy density and high efficiency indicate that relaxor PLZT with La/Zr/Ti=8/52/48 is a promising candidate for high-power film capacitors. [Copyright &y& Elsevier]

Rayleigh analysis has been used to investigate the temperature dependence of the dielectric response of relaxor ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 films grown on platinized silicon substrates by chemical solution deposition. The irreversible contribution to dielectric permittivity maximizes at 50 °C and decreases with further temperature increase; while the intrinsic/reversible contribution is weakly dependent on temperature. The relaxor ferroelectric transition temperature Tm increases from 160 °C to 172 °C when the frequency increases from 1 kHz to 100 kHz. The dielectric nonlinearity decreases with temperature: falling from 0.012 cm/kV at room temperature to 0.005 cm/kV at 225 °C in tests at 1 kHz. [ABSTRACT FROM AUTHOR]

We report the epitaxial growth of multiferroic BiFeO3 (BFO) film on Si(001) substrate by pulsed laser deposition using CeO2/yttria-stabilized zirconia (YSZ) as buffer layers. The epitaxial relationships of the films were BFO(001)/CeO2(001)/YSZ(001)/Si(001) for out-of-plane and [110]BFO|[100]CeO2|[100]YSZ|[100]Si for in-plane, respectively. Capacitance-voltage characteristics of a Pt/BFO/CeO2/YSZ/p-Si capacitor exhibited clockwise hysteresis loops with a large memory window of 2.5 V at sweeping voltages of ±16 V. Both the high and low capacitance values showed no obvious degradation after 104 s. The improved retention property was attributed to the use of high-k CeO2/YSZ insulating layers that effectively eliminated the charge trapping in the heterostructure. [ABSTRACT FROM AUTHOR]

Pure BiFeO3 (BFO), Eu doped BFO (BEF), and Nd doped BFO (BNF) multiferroic films were prepared by pulsed laser deposition on Pt/Ti/SiO2/Si substrates. XRD analysis revealed that the films had the rhombohedral structure with doping-induced lattice distortion. The Eu and Nd doping significantly improved the dielectric, ferroelectric, and ferromagnetic properties of the BFO films. Saturated hysteresis loops were observed in BEF and BNF films with remnant polarization of 37 μC/cm2 and 60 μC/cm2, respectively. The magnetization was demonstrated with remnant magnetization of 0.10 emu/cm3 and 0.60 emu/cm3 for the BEF and BNF films, respectively. The improvements and mechanism of different element doping on the properties of the BFO films were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Pure BiFeO3 (BFO), 15% Nd doped BFO (BNF), and 15% Nd and 2% high-valence Mn co-doped BFO (BNFM) multiferroic ceramics were prepared by a rapid liquid phase sintering technique. A structural transition from rhombohedral to orthorhombic occurred in the BNF and BNFM ceramics. The co-doped BNFM ceramics exhibit the largest dielectric constant, the smallest dielectric loss and leakage current, and an improved rectangular-shaped polarization hysteresis loop with a remnant polarization as high as 31 μC/cm2, which could be attributed to the lower concentration of charge defects and the structural transition. Besides, enhanced ferromagnetism is confirmed in BNFM with a remnant magnetization of 0.075 emu/g and a coercive magnetic field of 5.8 kOe, which might be attributed to the effective suppression of the spatially modulated spin structure by the Nd and Mn co-doping. [Copyright &y& Elsevier]

A barbell-shaped magneto-mechano-electric (MME) device for low-frequency magnetic field energy harvesting is proposed and investigated, exhibiting a maximum output power of 10.5 μW under 10 Oe AC magnetic field at its resonate frequency (˜36.6 Hz). • The properties of the magneto-mechano-electric (MME) energy harvester are optimized by using the finite element analysis. • Supported by the finite element analysis, the effect of electrode shape on barbell-shaped device's performance is studied. • The proposed MME device presents a low resonate frequency (<50 Hz), a magnetoelectric coefficient higher than 1 V/cm Oe. • The proposed MME energy harvester shows a high output voltage (>10 V @ 10 Oe) and a maximum output power of ∼10.5 μW. A magneto-mechano-electric (MME) device for energy harvesting from ambient low-frequency magnetic field is investigated in this study. Consisting of piezoelectric ceramic rings, NdFeB permanent magnets and union piece, the proposed MME energy harvester is designed with the barbell-shaped structure operating in d 33 mode. NdFeB permanent magnets are attached at the free end of barbell-shaped structure, which can produce compressive stress on the piezoelectric ceramic rings via magnetic torque effect. The properties of the MME energy harvester are optimized by using the finite element analysis. Two electrode shapes, including full electrode and divided electrode, are investigated in the aspect of their influences on the device performance. The finite element analysis is consistent with the experimental results, revealing that the electrode shape of piezoelectric ceramic rings is crucial for the performance of the proposed MME device. The MME device presents a low resonant frequency (<50 Hz), a magnetoelectric coefficient higher than 1 V/cm Oe, a high output voltage (>10 V @ 10 Oe), a maximum output power of ˜10.5 μW and a maximum power density of 3.5 μW/Oe cm3, demonstrating the potential applications for harvesting ambient low-frequency magnetic field energy. [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]

Currently, a widely accepted solution to reduce gypsum precipitation in acid leaching of low-grade uranium ore has not yet been identified. This study aims to delve into the impact of different flow rates on gypsum precipitation in ore through column leaching experiments. Complementary methods such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to characterize slag samples. The results indicate that as the flow rate surged from 63.69 Lh−1m−2 to a whopping 254.76 Lh−1m−2, the gypsum content and types in the slag decreased gradually. This can be attributed to two factors: (1) the elevation of flow rates maintains the ore heap in a lower pH environment, promoting the conversion of SO42− to HSO4−; (2) higher flow rates contribute to increased ore heap porosity, providing more migration pathways for solutions containing high concentrations of Ca2+, SO42−, and HSO4−, thus facilitating the separation of gypsum from the ore. This study affirms the feasibility of employing high-flow pre-leaching to address gypsum clogging issues, offering a new perspective for acid pre-leaching. [ABSTRACT FROM AUTHOR]

Half-metallic NiCo2O4 with high spin polarizability has great potential applications in spintronics. The manipulation of magnetic anisotropy is crucial for spintronics based on spin-transfer or spin–orbit torques, as it is directly related to the critical switching current density. Here, we report epitaxial growth of metallic NiCo2O4 film with perpendicular magnetic anisotropy on MgAl2O4 single crystal substrates. The modulation of the magnetic anisotropy was achieved by changing the growth conditions (deposition temperature and thickness) of NiCo2O4 films and by means of protonation. Strong dependence of magnetic coercivity on deposition temperature (350–500 °C) has been observed due to variable phase configuration. Furthermore, the magnetic coercive field can also be effectively controlled by the film thickness (3–78 nm) through strain relaxation. More importantly, spin reorientation transition has been achieved by proton and electron doping in the NiCo2O4 films, resulting in reconfigured valence states of Ni and Co cations and a magnetic easy axis rotation from out-of-plane to in-plane. The effective modulation of the magnetic anisotropy provides important insights into the functional design of NiCo2O4-based spintronics with ultralow energy dissipation. [ABSTRACT FROM AUTHOR]

MnZn ferrites that exhibit low core losses at high frequencies are suitable for the integration and miniaturization of power conversion devices. To obtain low core losses at high frequencies, it is important to understand the underlying mechanism. In this work, MnZn ferrites with various grain sizes were produced by changing the sintering temperature. The relationship between domain morphology, dynamic magnetization behavior, and core losses at high frequencies was carefully investigated. As the average grain size approached the critical size of single‐domain state, the contribution of domain wall displacement to complex permeability decreased, while domain wall resonant frequency improved significantly, resulting in the suppression of residual loss at 3 MHz. As the average grain size increased, the domain morphology changed from a single‐domain state to a multidomain state, which increased the initial permeability and decreased hysteresis loss. However, the number of domain walls increased, causing a significant decrease in the domain wall resonant frequency, and resulting in a sharp increase in residual loss. These results provide valuable insights into reducing high‐frequency core losses in MnZn ferrites by domain engineering. [ABSTRACT FROM AUTHOR]

Jarosite has shown excellent adsorption capacity in heavy metal adsorption processes. In this study, jarosite was synthesized using different methods, including the bio-oxidation by Acidithiobacillus ferrooxidans (BAF), rapid addition of H2O2 (RAH), and slow addition of H2O2 (SAH). The synthesized jarosite samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The influence of pH, adsorption time, and adsorbent dosage on the adsorption performance of U(VI) by jarosite was investigated through static adsorption experiments. The results revealed that jarosite with petal-like, granular, and spherical morphologies was obtained using the BAF, RAH, and SAH methods, respectively. Among jarosite synthesized by the three methods, bio-synthesized jarosite exhibited the best adsorption performance, with a maximum adsorption capacity of 96.2 mg/g for U(VI). Under the conditions of pH 7 and an adsorbent dosage of 0.8 g/L, the adsorption equilibrium was reached within 80 min. The adsorption process of U(VI) by jarosite synthesized through three methods all followed the Langmuir model. Adsorption kinetics follow a pseudo-second-order rate expression, indicating a chemical interaction between the adsorbent and the presence of U(VI). These results suggest that bio-synthesized jarosite has great potential for adsorbing U(VI) from U(VI)-contaminated wastewater. [ABSTRACT FROM AUTHOR]

Unidirectional magnetic anisotropy induced by exchange bias (EB) between ferromagnetic and antiferromagnetic layers is of paramount importance in various spintronic devices. Traditional setting and optimization of EB involve cooling through the Néel temperature of the antiferromagnets under biasing field in vacuum furnace which takes hours of time and cannot realize localized control of EB. Herein, an alternative process to configure EB by injection of microsecond current impulse for locally heating of the heterostructure is reported. 180‐degree exchange bias switching has been realized in both anisotropic magnetoresistance and giant magnetoresistance units, resulting in tunable magnetic field sensing functionalities. This mechanism for pinpoint control of EB provides more freedom for the design and optimization of various sensing and logic spintronics. [ABSTRACT FROM AUTHOR]

The micro-discharge effect is a failure mechanism that often appeared in space microwave devices under vacuum conditions, such as RF (radio frequency) cavity, RF satellite missile, and antenna launching communication system. How to control micro-discharge effectively and simply has become a research hotspot. In this paper, we have prepared a series of doping silver (Ag)/carbon (C) composite films by double target magnetron sputtering technology and have significantly reduced the maximum secondary electron emission coefficient (δmax) from 2.522 to 1.04 when the doping ratio of Ag/C is 1.345. Theoretically, the continuous increase of sp2 hybrid bond content tuned by the existing Ag nanoparticles has a greater contribution to the conductivity and inhibition of secondary electron emission in the Ag/C composite films. Meanwhile, the gradually emerged "multi-trap" surface structure with the increase of Ag doping content has further increased the collision between excited secondary electrons and free electrons, achieving an obvious inhibition effect. The results demonstrate that secondary electron emission can be suppressed effectively by tuning the structural feature of two kinds of compounded materials with low δmax. It is of great significance in physical mechanism analysis and design of the new doping process. [ABSTRACT FROM AUTHOR]

Strain-mediated magnetoelectric effect can be utilized as an energy-efficient approach for spin manipulation. However, over 90° magnetization rotation is still challenging in un-patterned magnetic films, as the piezo-strain driven by ferroelectric domain switching is generally uniaxial rather than unidirectional, which limits the developments of non-volatile magnetic memory and logic devices. Here we demonstrate the rotation of local magnetization with a large angle of 136° by applying strains with a shear component at a fixed magnetic field of 45 Oe in FeCoSiB/PMN-PT (011) multiferroic heterostructures, revealed by a vector-resolved quantitative magneto-optical Kerr effect (MOKE) microscopy. Phase-field simulations confirm that the approximate 140° rotation of magnetization vectors is a consequence of the shear strain associated with ferroelectric/ferroelastic switching of PMN-PT (011) substrates. The visualization of over 90° magnetization rotation induced by the strain with a shear component paves the way for deterministic magnetization switching that has important implications in the energy-efficient spintronic devices. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The domain structure fundamentally determines the piezoelectric/ferroelectric performance of ferroelectric materials. To understand the correlation between macro-properties and microstructure, the evolution of domain structure should be clearly figured out. Here, the diffraction-plane-transformation (DPT) model is proposed for the domain evaluation in BS-PT piezoelectric ceramics of rhombohedral crystalline structure. The transformation between different crystal planes is accurately revealed by the DPT model. Then, non-180° domain reversal in rhombohedral 0.4BiScO3–0.6PbTiO3 piezoelectric ceramics (abbreviated as BS-PT) can be quantitatively estimated, whether in electric poling or thermal depoling processes. Experimentally, the correlations between piezoelectric coefficients, electromechanical coupling properties, and non-180° domain reversal percentage are investigated. It is proven that the DPT model provides an effective method for the non-180° domain estimation in rhombohedral crystalline ceramics. [ABSTRACT FROM AUTHOR]

Highlights: The (001)-oriented ferromagnetic La0.67Sr0.33MnO3 films are stuck onto the (011)-oriented ferroelectric single-crystal 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 substrate with 0° and 45° twist angle. By applying a 7.2 kV cm−1 electric field, the coexistence of uniaxial and fourfold in-plane magnetic anisotropy is observed in 45° Sample, while a typical uniaxial anisotropy is found in 0° Sample. Manipulating strain mode and degree that can be applied to epitaxial complex oxide thin films have been a cornerstone of strain engineering. In recent years, lift-off and transfer technology of the epitaxial oxide thin films have been developed that enabled the integration of heterostructures without the limitation of material types and crystal orientations. Moreover, twisted integration would provide a more interesting strategy in artificial magnetoelectric heterostructures. A specific twist angle between the ferroelectric and ferromagnetic oxide layers corresponds to the distinct strain regulation modes in the magnetoelectric coupling process, which could provide some insight in to the physical phenomena. In this work, the La0.67Sr0.33MnO3 (001)/0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (011) (LSMO/PMN-PT) heterostructures with 45º and 0º twist angles were assembled via water-etching and transfer process. The transferred LSMO films exhibit a fourfold magnetic anisotropy with easy axis along LSMO < 110 >. A coexistence of uniaxial and fourfold magnetic anisotropy with LSMO [110] easy axis is observed for the 45° Sample by applying a 7.2 kV cm−1 electrical field, significantly different from a uniaxial anisotropy with LSMO [100] easy axis for the 0° Sample. The fitting of the ferromagnetic resonance field reveals that the strain coupling generated by the 45° twist angle causes different lattice distortion of LSMO, thereby enhancing both the fourfold and uniaxial anisotropy. This work confirms the twisting degrees of freedom for magnetoelectric coupling and opens opportunities for fabricating artificial magnetoelectric heterostructures. [ABSTRACT FROM AUTHOR]

Abstract The magnetoelectric (ME) materials and related devices have been attracting increasing research attention over the last few years. They exhibit strong ME coupling effect at room temperature, and electric field control of magnetization or magnetic field control of ferroelectric polarization can be achieved. The ME coupling effect brings novel functionalities to develop ultra-fast, low-power, and miniaturized electronics. Recent progress shows the performance of ME materials is further improved and the materials are used to develop many new types of electronics such as high-speed memory, radio frequency resonator, compact ME antenna, and weak magnetic field sensor. In this review, we present the overview in those fields with emphasis on both the opportunities and challenges for the application of ME materials and devices in the cutting-edge technologies. Highlights • Magnetoelectric material exhibit interconnections of magnetic and electric field. • ME applications can be classified as direct coupling and converse coupling. • There are various ME devices including sensor, antenna and microwave devices. • ME devices show better performance and the potential to be miniaturized. • Nan's ME antenna prototype is two orders of magnitude smaller than conventional one. [ABSTRACT FROM AUTHOR]

• Epitaxial NiCo 2 O 4 thin films with strikingly different magnetic and electric properties have been deposited by varying of growth conditions. • Paramagnetic to ferrimagnetic phase transformation has been realized in the NCO film grown with relatively low temperature by proton doping. • With exquisite engineering of the phase configuration of NCO, the magnetoresistance could be increased by more than 400%. Element doping and substitution have been widely used for the engineering of the electronic structure and macroscopic magnetic properties of various materials. However, traditional doping process does not allow further optimization after preparation of the samples. Hydrogen annealing-induced protonation has emerged as a powerful method for the efficient control of uniaxial lattice expansion to modulate the physics properties of the otherwise inaccessible novel correlated phases in oxide thin-films. Here, we report the modulation of the magnetic moment, magneto-transport and electrical-transport in inverse-spinel NiCo 2 O 4 (NCO) by protonation. Strong dependence of saturation magnetic moment and electrical conduction on deposition temperature and proton doping parameters has been systematically investigated. The magnetoresistance ratio of the protonated NCO could be increased by 400% by engineering of the doping condition and thus the phase configuration. These findings indicate that protonation is one effective strategy for regulation and optimization of NCO-based magnetic and electric devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To achieve compact and lightweight power conversion devices, magnetic core materials such as MnZn ferrite are highly desired with low core losses at high frequencies above megahertz. In this work, high-valent Sn4+ ions were doped into MnZn ferrite to manipulate the electromagnetic properties and suppress the high-frequency core losses. The distribution of Sn4+ in MnZn ferrite was investigated by transmission electron microscopy with energy dispersive x-ray analysis, which indicated that most of the substituted Sn4+ ions remained at the grain boundaries rather than dissolving into the lattice, and thus greatly impacted the electromagnetic properties of MnZn ferrite. The initial permeability and saturation induction decreased monotonically with the Sn substitution. The core loss was reduced to 457 kW m−3 at 3 MHz, 30 mT, and 25 °C when the Sn substitution content was 0.003, due to the effective suppression of eddy current loss and residual loss. The sample with a Sn content of 0.003 exhibited excellent overall electromagnetic properties, which could be potentially useful in high-frequency transformers, converters, and power sources. [ABSTRACT FROM AUTHOR]

The emerging market of wearable devices for tracking and positioning requires the development of highly flexible magnetic sensors. Due to the stable magnetoresistance ratio and simple fabrication process, sensors based on the anisotropic magnetoresistance (AMR) effect have been proposed as promising candidates. However, the stability of AMR sensors under different bending situations has rarely been investigated. In this work, we proposed a flexible AMR magnetic sensor deposited on an ultra-thin Kapton substrate, which exhibits excellent anti-fatigue behavior at different bending curvatures ranging from 1/3 to 1/10 mm−1. Experimental results show that the sensitivity of our proposed flexible AMR sensor remains as high as 0.25 Oe−1 after being bent 500 times, showing promising potential for application in wearable electronic devices. [ABSTRACT FROM AUTHOR]

We report a continuously tunable resistive switching behavior in Pt/BiFeO3/Nb-doped SrTiO3 heterostructure for ferroelectric memristor application. The resistance of this memristor can be tuned up to 5 × 105% by applying voltage pulses at room temperature, which exhibits excellent retention and anti-fatigue characteristics. The observed memristive behavior is attributed to the modulation effect of the ferroelectric polarization reversal on the width of depletion region and the height of potential barrier of the p-n junction formed at the BiFeO3/Nb-doped SrTiO3 interface. [ABSTRACT FROM AUTHOR]

Ferroelectric Pb0.92La0.08Zr0.52Ti0.48Oδ films (≈2-μm thickness) were grown on LaNiO3-buffered nickel foils by chemical solution deposition. Their ferroelectric and dielectric properties were measured as a function of temperature. With increasing temperature from room temperature to 200 °C, back-switching polarization increased while spontaneous polarization, remanent polarization, and coercive field decreased. The domain wall energy barrier was determined from the temperature-dependent back-switching polarization. Decreased irreversible/extrinsic and reversible/intrinsic dielectric responses were observed with increasing frequency. The ratio of irreversible to reversible contributions to dielectric nonlinearity was analyzed by the Rayleigh law. This ratio decreased with increasing frequency from 500 Hz to 500 kHz. [ABSTRACT FROM AUTHOR]

The magnetic field sensors based on anisotropic magnetoresistance (AMR) effect have been widely used in data storage, navigation, and medical diagnosis. However, the AMR effect of metal materials is relatively weak with an AMR ratio below 2%, which results in low voltage output. In order to improve the sensitivity of weak magnetic fields, we optimize the structure of the AMR sensor with a specific photolithographic process. We use two different designs of Hall bar and Wheatstone bridge with similar barber pole structures, and investigate the angular dependence as well as magnetic field dependence of AMR ratio and voltage output. With Wheatstone bridge, the magnetoresistance leads to a voltage output without dc components. The NiFe magnetic layer and the Au electrode are patterned into a highly conductive barber poles structure, and a high voltage output ratio of about 80% is obtained. At the same time, we achieve a high sensitivity of about 4.3 Oe−1, which implies potential applications in AMR effect-based magnetic field sensors. [ABSTRACT FROM AUTHOR]

We incorporated a ≈5-nm-thick MnO x insertion layer in the middle of a ≈1.38-μm-thick Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 (PLZT) film grown by a modified sol–gel process and measured the dielectric and ferroelectric properties of PLZT films with and without MnO x insertion layer. By incorporation of the MnO x layer, residual stress was reduced from ≈350 MPa to ≈125 MPa, dielectric permittivity decreased from ≈1300 to ≈950, while dielectric loss increased from ≈0.04 to ≈0.07 as measured at 10 kHz. Also, remanent polarization increased from ≈9.1 μC/cm 2 to ≈11.7 μC/cm 2 , coercive field increased from ≈28.7 kV/cm to ≈40.3 kV/cm, and internal bias field from ≈3 kV/cm to ≈14 kV/cm. We have observed decreased irreversible Rayleigh coefficient and dielectric nonlinearity on samples with MnO x insertion layer. These changes in properties are attributable to Mn cation doping as acceptors near the MnO x /PLZT interface, which forms oxygen vacancies and defect induced dipoles like 2 M n ′ T i − V O • • (or M n ″ T i − V O • • ), acting effectively as pinning centers to hinder domain wall movement. [ABSTRACT FROM AUTHOR]

Large working range is of vital importance for magnetic sensors when exposed to complicated magnetic field profile, especially in automation and power industry where large field variation is frequently encountered. The design for traditional magnetic sensors, e.g., magnetoresistive and fluxgate magnetometers, utilizes ferromagnetic materials with ultrahigh permeability to maximize the field sensitivity, resulting in strictly confined dynamic range due to limited saturation field. Here, an integratable ferromagnetic resonance (FMR) prototype magnetic sensor with high sensitivity and theoretically unlimited working range is reported. An ultrawide working range (>450 mT) which is more than two orders larger than that of commercial sensors with similar field resolution is experimentally verified. Moreover, the FMR magnetometer is a vector sensor in contrast to the traditional scalar sensors based on magnetic resonance. With a navigating magnetic field of 50 μT (ca. the Earth's magnetic field), the resolution for azimuth angle is 0.006°. Compared with traditional nuclear magnetic resonance and electron paramagnetic resonance sensors with large size and high power consumption, the compact FMR sensor with large dynamic range and high sensitivity has much broader application prospects, especially in magnetically harsh environments. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the bipolar resistive switching effect in a SrTiO3/NiO stacked heterostructure which was epitaxially deposited on an Nb doped SrTiO3 substrate by pulsed laser deposition. This heterostructure shows high resistive switching ratio of over 104 at the read voltage of −0.5V and an expected retention ability of ten years, which is better than that of NiO-based device. Moreover, the resistive switching ratio can be adjusted by changing the maximum applied voltage or compliance current, which shows promising for multilevel nonvolatile memories application. Meanwhile, these results have been discussed by carrier injection-trapped/detrapped process. [Copyright &y& Elsevier]

Abstract: The CoFe2O4 (CFO)/Bi3.15Nd0.85Ti3O12 (BNT) multiferroic composite coaxial nanotubes were prepared by a sol–gel template method. The morphologies of the coaxial nanotubes were characterized and the selected area electron diffraction patterns confirmed the coexistence of spinel CFO and perovskite BNT phase. The vibrating sample magnetometer measurements showed that the saturation magnetization and coercive field of the coaxial nanotubes were 1emu/g and 0.7kOe, respectively, which was contributed totally from the inner CFO nanotubes. The CFO/BNT coaxial nanotubes showed typical ferroelectric hysteresis loop, while the increased leakage current density is likely due to the high conductivity in the inner CFO nanotubes. Our study demonstrated that the CFO/BNT coaxial nanotubes were of both ferroelectric and magnetic features in nanoscale. [Copyright &y& Elsevier]

-site Ce and B-site Zr codoped BiCeFeZrO (BCFZ) thin films with different compositions were successfully prepared on the Pt/Ti/SiO/Si substrates by chemical solution deposition. The influence of the A-site Ce and B-site Zr codoping on the structure, surface morphology, electrical and magnetic properties of BFO films were investigated, respectively. The comparative study suggested that the A-site Ce doping with various contents have notable influences on the electrical properties of the BFO films, while the B-site Zr doping with different contents affect mainly the magnetic properties of the BFO films. Compared with the other BCFZ films studied here, the BiCeFeZrO film showed the lowest dielectric loss and leakage current density, a well-squared P- E loop and fatigue-free characteristics as well as the strong magnetization. [ABSTRACT FROM AUTHOR]

Zn/Al co-doped nickel ferrites (NZAFO) with ultralow magnetic damping and large magnetostriction are critically needed for use in tunable spintronic devices and dissipationless quantum computation. However, the growth of epitaxial NZAFO thin films with optimized properties is difficult due to their tendency to form anti-site defects and antiphase boundaries, even on isostructural spinel substrate. Here, growth temperature-dependent ferromagnetic resonance (FMR) and magnetization have been systematically investigated. The saturate magnetization and damping linewidth have decreased from 114 to 70 emu/cc and 321 to 12 Oe as deposition temperature increased from 500 °C to 650 °C, respectively. With further optimization of the film thickness, a minimum FMR linewidth of 7.5 Oe has been observed, only 1.74% of that of bulk form NZAFO materials. Further increasing of deposition temperature to 700 °C results in a dramatic increase in the magnetic coercive field and damping linewidth. The magnetostriction and magnetocrystalline anisotropy are relatively stable in a large temperature range. The strong dependence between magnetic properties and the deposition temperature has been explained in terms of cation redistribution and evaporation. The insulating ferrimagnetic NZAFO with ultralow microwave loss and strain tunable static and dynamic magnetic properties serve as a promising candidate to be used in various tunable electronic devices. [ABSTRACT FROM AUTHOR]

Magnetic sensors have various applications in navigation, power distribution, robotics, factory automation, and medical diagnosis. The development of highly sensitive magnetic sensors usually requires complicated and costly fabrication process. Herein, we report giant magneto-impedance of 41036% in the commercially available ferrite core inductors. A magnetic field detection limit of 10 nT at 1 Hz has been obtained by directly measuring the impedance of the as-obtained inductor without any optimization. With a 100 pF capacitor in series connection with the inductor where lower impedance facilitates the measurement process, a limit of detection of 625 pT at 1 Hz has been obtained in the series RLC resonator. These results can be understood in terms of the magnetic field-dependent self-resonance in the inductors which act as lumped RLC resonators. Compared with the traditional electromagnetic induction sensing mode, the magneto-impedance sensing mode shows 5000 folds improvement in the magnetic field detection capability. [ABSTRACT FROM AUTHOR]

Voltage-tunable RF/microwave devices attract great attention due to their low power consumption; however, they still suffer from the fundamental dilemma between large tunability and low insertion loss. In this paper, yttrium iron garnet (YIG) polycrystalline thin films with low microwave loss (<3 × 10−4) were directly deposited on mica substrates via a van der Waals force and then transferred onto PMN-PT substrates. The in-plane magnetic anisotropy of YIG was tuned by the in-plane biaxial stress of PMN-PT, and an improved voltage tunability (175 MHz) of in-plane FMR fr was obtained due to the removal of the substrate clamping effect. Moreover, our samples still represent good frequency stability (4–12 GHz) during the tuning process. It is of significance for exploiting novel, portable, low-loss RF/microwave devices in the future. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composites exhibit extremely high sensitivity for magnetic field at the fixed resonant frequency, due to the strong strain-mediated ME coupling. However, wideband magnetic field detection is still challenging, as the ME coefficient depends strongly on the frequency. In this work, we propose a magnetoelectric sensor composed of three ME units in series/parallel connections, which works at dual modes to extend the frequency range with high signal-to-noise ratio (SNR). The SNR is enhanced by about 22.68 dB and the bandwidth is broadened from 100 Hz to 1 kHz, with a high sensitivity for frequency conversion mode by series/parallel connections. Limits of detections (LoDs) as low as 207 pT and 460 pT are demonstrated at 1 kHz and 100 kHz, respectively, showing promising applications in wideband magnetic field detection. [Display omitted] • We propose a magnetoelectric sensor that works in frequency conversion at 1–1000 Hz and passive mode at 1–100 kHz. • We found a way to enhance the SNR and the bandwidth of frequency conversion, without sweeping the modulation field. • Our device is suitable for pico-Tesla (pT) level magnetic field detection in broadband. [ABSTRACT FROM AUTHOR]

Perovskite materials with compositions in the vicinity of the steep morphotropic phase boundary (MPB) exhibit various intriguing properties including giant piezoelectricity and large dielectric constant. Aside from composition, the phase configuration of the perovskites is also strongly related to the ambient temperature. Here, we report a giant piezoelectricity of 10 980 pm/V at 93°C in the 0.7Pb(Mg1/3Nb2/3)O3‐0.3PbTiO3 (PMN‐PT) single crystals which is more than five times larger than that at room temperature. The enhanced piezoelectricity can be attributed to the instability of the thermally induced tetragonal phase which can be converted to the orthorhombic phase by the external electric field in the <011> oriented single crystal. The transverse piezoelectricity has been investigated by measuring the electric‐field‐dependent ferromagnetic resonance (FMR) field in the CoFeB/PMN‐PT magnetoelectric (ME) heterostructures. The ME coupling coefficient has been increased from 49.3 to 476 Oe cm/kV as temperature increased from 25 to 90°C. The findings reveal that both longitudinal and transverse piezoelectricity in the PMN‐PT single crystals can be greatly enhanced by proper setting of ambient temperature, indicating an effective route for the design of strain‐mediated tunable devices with ultralow driving voltage. [ABSTRACT FROM AUTHOR]

Wireless strain sensors have received extensive attention owing to their wide application prospects in structural health monitoring, industrial automation, human activity monitoring, and intelligent robotic systems. Here, a wireless strain sensor prototype based on the magnetoelectric heterostructure of ferromagnetic thin films on a piezoelectric substrate has been developed. The ferromagnetic resonance (FMR) frequency of the sensor is strongly dependent on external strain due to the large magnetostriction of the film. The piezoelectric substrate with a programmable voltage has been used as a strain source for the characterization of the wireless strain sensor. The limit of detection of the wireless strain sensor is 0.54 με, which is comparable with that of commercial metal-foil sensors that need connection wires. More importantly, the FMR strain sensor shows a sensitivity of 65.46 ppm/με, indicating more than a 60 fold improvement than that of traditional wireless strain sensors based on patch antenna and RLC resonators whose frequency shift is mainly due to the strain induced dimension change. [ABSTRACT FROM AUTHOR]

High-valence Pr-doped BiFeO3 (BPF) multiferroic thin film was prepared by pulsed laser deposition on a Pt/TiO2/SiO2/Si substrate. X-ray diffraction analysis indicates that the BPF film is of pure phase with a polycrystalline perovskite structure. The BPF film exhibited enhanced multiferroic properties: (i) a rectangular-shaped electric hysteresis loop with a large Pr of 75 μC/cm2 and a low Ec of 250 kV/cm at Emax ∼620 kV/cm, (ii) a saturated magnetic hysteresis loop with a large Ms of 58 emu/cm3, and (iii) a fatigue-free behavior after being subjected to 1.2×109 switching cycles, which were superior to, in some aspects, those of La- or Nd-doped BiFeO3 films reported before. [ABSTRACT FROM AUTHOR]

• Surface engineered Ag/Al substrates by carbon coating for space microwave devices. • K s factor is extracted from the angular-dependent SEY coefficient measurement by using the Vaughan model. • Low-cost, easy-to-scale process is provided to reduce the SEY coefficient by 35%. High power microwave devices have been suffering from secondary electron yield (SEY), which occurs at the surface and leads to increases in energy dissipate and noise level in microwave cavities. The suppression of SEY in microwave materials is significant for space applications. In this work, we report a surface roughness evolution mechanism induced by carbon coating on a widely-used microwave cavity material Ag/Al. The competition between the preferred growth and the island growth modes leads to the roughness enhancement in the 60 nm carbon coated Ag/Al substrates. By extracting the smooth factor K s in Vaughan model from the angular dependent SEY measurement, we attribute the suppression of SEY to the intrinsic low SEY of the carbon film and the high surface roughness. Our work demonstrates a low-cost, easy-to-scale coating process to effectively prevent the formation of secondary electron avalanche in space borne microwave devices. [ABSTRACT FROM AUTHOR]

Voltage control magnetism is one of the most energy efficient pathway towards magnetoelectric (ME) device. Ionic liquid gating (ILG) method has already shown impressive manipulation power at the IL/electrode interface to influence the structure, orbital as well as spin of the electrode materials. As key material in anisotropy magnetoresistance sensor and spin valve heterostructure, the permalloy Ni 0.81 Fe 0.19 was utilized as the electrode to investigate the ILG induced magnetic anisotropy change. In this work, we realized magnetic anisotropy control in Au/[DEME]+[TFSI]-/Ni 0.81 Fe 0.19 (2.5 nm)/Ta heterostructure via ILG caused electrostatic doping. This is evidenced in situ reversible ferromagnetic field (H r) shift with electron spin resonance (ESR) spectrometer. Aiming at the question whether the charge accumulation at the ionic liquid interface is the main control mechanism at low voltage, we carefully tested the relationship between the change of resonance field and the amount of surface charge. It was found that these two had a good linear relationship between −1 V and +1 V. Defining the linear parameter as A whose value is 28.7 mT m2/Col. Unlike previously reported chemical regulation of Co, this article used ionic liquids to physically regulate NiFe, which has not been studied in the previous ionic liquid regulation. And NiFe has a narrower resonance line width for easy reference to microwave devices. In addition, It also has a stronger ferromagnetic signal than Co, which can be more easily detected as a sensor device. Therefore, this system is more promising. The ILG control NiFe may lead to a new kind of magnetoelectric sensor devices and path a new way to low energy consumption spintronics. • We demonstrate the feasibility of low voltage (1 V) regulation of magnetic anisotropy. • A linear relationship between the surface charge density and the resonance field offset was observed and the linear coefficient was calculated to be 28.7 mT m2/Col. [ABSTRACT FROM AUTHOR]