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In our experiment, the influence of growth parameters of the spin-spray technique upon the microstructure and magnetic/microwave properties of NiZn spinel ferrite thin film was studied. By varying the pH value of precursor and oxidizer, the microstructure of NiZn ferrite thin film can be manipulated, further, bringing varying magnetic/microwave properties. High permeability μ′ > 200 at 0.5 GHz with low loss tanδ ~0.027 at 3-5 GHz range was achieved at precursor pH value of 4.6 and oxidizer pH value of 9.6. These magnetic/microwave properties are ideal for GHz range microwave application, for example, inductors, antennas, and electromagnetic interference suppression. [ABSTRACT FROM AUTHOR]

We deposited ferroelectric (Pb0.92La0.08)(Zr0.52Ti0.48)O3 films of ≈0.35 to ≈3.1 μm in thickness on platinized silicon substrates by chemical solution deposition. A dielectric constant of ≈1350 and dielectric loss of ≈0.04 were measured at room temperature. Hysteresis loop tests revealed that the remanent polarization increases while the coercive field decreases with PLZT film thickness. The residual stress in the PLZT films, as determined by the x-ray diffraction sin2ψ method, decreased from ≈380 to ≈200 MPa when the film thickness increased from 0.35 to 3.1 μm. The dependence of the residual stress (σ) on the PLZT film thickness (t) can be described by an empirical equation, σ = A0exp(−t2/λ2), with A0 ≈ 390 MPa and λ ≈ 3.8 μm. [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]

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]

Magnonics or spin waves have the potential to serve as the carrier for future information communication. A controllable spin wave resonance (SWR) device is demonstrated in a Au/[DEME]+[TFSI]−/LSMO/STO capacitor heterostructure, which could be regulated by ionic liquid gating (ILG) method. The SWR critical angle φC, excitation position to perform uniform precession, is shifted in a reversible manner (thus recording "off" and "on") with +1.5 V gating voltage (Vg), measured by quantitative angular dependent electron spin resonance (ESR) spectroscopy. Based on the modified Puszkarski's surface inhomogeneity model, the ILG control SWR at low Vg (Vg < 1.5 V) can be explained by a charge‐doping‐induced effective surface magnetic anisotropy change. Applying a higher Vg (Vg > 1.5 V) enhances the surface mode SWR and gradually diminishes the body mode SWR. Oxygen vacancies generate at higher Vg (Vg > 1.5 V) resulting in the modulation of superexchange between the Mn ions, evidenced by X‐ray photoelectron spectroscopy and secondary ion mass spectroscopy characterization. This ILG control SWR presents a solution for energy efficient and low‐voltage control of magnonics and spin wave devices. [ABSTRACT FROM AUTHOR]

Magnetization dynamics induced by spin–orbit torques in a heavy‐metal/ferromagnet can potentially be used to design low‐power spintronics and logic devices. Recent computations have suggested that a strain‐mediated spin–orbit torque (SOT) switching in magnetoelectric (ME) heterostructures is fast, energy‐efficient, and permits a deterministic 180° magnetization switching. However, its experimental realization has remained elusive. Here, the coexistence of the strain‐mediated ME coupling and the SOT in a CoFeB/Pt/ferroelectric hybrid structure is shown experimentally. The voltage‐induced strain only slightly modifies the efficiency of SOT generation, but it gives rise to an effective magnetic anisotropy and rotates the magnetic easy axis which eliminates the incubation delay in current‐induced magnetization switching. The phase field simulations show that the electric‐field‐induced effective magnetic anisotropy field can reduce the switching time approximately by a factor of three for SOT in‐plane magnetization switching. It is anticipated that such strain‐mediated ME‐SOT hybrid structures may enable field‐free, ultrafast magnetization switching. A strain‐mediated magnetoelectric‐spin‐torque hybrid structure, which combines the advantages of spin orbit torque‐ and magnetoelectric‐ driven magnetization dynamics together, is developed. Via a magentoelectric effect, voltage‐controlled magnetic anisotropy is demonstrated in spin–orbit torque devices, which can lead to a reduction of the magnetization switching time by a factor of three. The findings provide a new platform for fast and low‐power spintronics. [ABSTRACT FROM AUTHOR]

Ferromagnetic insulator thin film nanostructures are becoming the key component of the state‐of‐the‐art spintronic devices, for instance, yttrium iron garnet (YIG) with low damping, high Curie temperature, and high resistivity is explored into many spin–orbit interactions related spintronic devices. Voltage modulation of YIG, with great practical/theoretical significance, thus can be widely applied in various YIG‐based spintronics effects. Nevertheless, to manipulate ferromagnetism of YIG through electric field (E‐field), instead of current, in an energy efficient manner is essentially challenging. Here, a YIG/Cu/Pt layered nanostructure with a weak spin–orbit coupling interaction is fabricated, and then the interfacial magnetism of the Cu and YIG is modified via ionic liquid gating method significantly. A record‐high E‐field‐induced ferromagnetic resonance field shift of 1400 Oe is achieved in YIG (17 nm)/Cu (5 nm)/Pt (3 nm)/ionic liquid/Au capacitor layered nanostructures with a small voltage bias of 4.5 V. The giant magnetoelectric tunability comes from voltage‐induced extra ferromagnetic ordering in Cu layer, confirmed by the first‐principle calculation. This E‐field modulation of interfacial magnetism between light metal and magnetic isolator may open a door toward compact, high‐performance, and energy‐efficient spintronic devices. A record‐high E‐field‐induced ferromagnetic resonance field shift of 1400 Oe is achieved in an yttrium iron garnet/Cu/Pt/ionic liquid/Au capacitor heterostructure with a small voltage bias of 4.5 V characterized via in situ electron spin resonance spectroscopy. The giant magnetoelectric tunability comes from voltage‐induced extra ferromagnetic ordering in the Cu layer, confirmed by the first‐principle calculation. [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]

• 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]

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]

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]

• 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]

Multiferroic Bi (1+x)×0.85 Nd 0.15 FeO 3 (BNF) ceramics with various Bi contents are prepared by conventional solid state reaction, and the effects of excess Bi on the structure, morphology, dielectric, ferroelectric, and magnetic properties are investigated. XRD patterns show the coexistence of rhombohedral and orthorhombic phase in all BNF ceramics due to the doping of Nd3+ ions. Bi 2 Fe 4 O 9 and Bi 2 O 3 impurity can be observed in x = 0 and x = 5%, 7.5% ceramics, respectively. Surface morphologies are closely related to the Bi content and x = 2.5% sample exhibits the largest average grain size of ∼6.72 μ m. The leakage current density has been decreased by 3–4 orders of magnitudes through excess Bi. The x = 2.5% sample shows good ferroelectric property with typical hysteresis loop and a large remnant polarization of about 42 μC/cm2 at 150 kV/cm. The P-E hysteresis deteriorates in x = 5% and x = 7.5% ceramics. The PbZrO 3 -like superstructure related to 1/4(hh 0) p diffraction spots in SAED pattern can be found in all BNF ceramics and the number of grain with superstructure observed in each sample decreases as the Bi content increases. As Bi content increases, the remnant magnetization decreases at first, and then increases. Conversion-electron Mossbauer study have ruled out the impacts of Fe2+, Fe4+, or γ-Fe 2 O 3 on the magnetic properties, suggesting that the weak ferromagnetism comes from the destroy of spin cycloid through substitution of Bi3+ ions with Nd3+ ions. Excessive Bi3+ ions have weakened the effect of Nd3+ ions on suppression of spin cycloid and resulted in the degradation of magnetic properties. The slight improvement of magnetic properties in x = 7.5% sample is considered to attribute to Fe vacancies induced by excessive Bi. • Bi (1+x)×0.85 Nd 0.15 FeO 3 ceramics (x = 0, 2.5, 5, and 7.5 mol%) were prepared. • Electrical properties are improved in Bi-excess ceramics. • The x = 2.5% ceramic shows good ferroelectric property. • The P-E hysteresis deteriorates in x = 5% and x = 7.5% ceramics. • Excess Bi leads to the decrease of magnetization and PbZrO 3 -like superstructures. [ABSTRACT FROM AUTHOR]

Magneto-mechano-electric (MME) generator converts magnetic energy into electrical energy via mechanical strain/stress mediated magnetoelectric coupling effect. However, the narrow operating bandwidth and low power density need to be improved for practical applications. In this work, by developing the constitutive equation of MME structure, we propose a hybrid multi-mode MME device with broadened bandwidth and enhanced energy harvesting performance. The designed hybrid generator includes three power generation units, which are piezoelectric energy harvesting (PEH) unit, electromagnetic energy harvesting (EEH) unit, and magnetostrictive energy harvesting (MEH) unit. Moreover, the corresponding energy harvesting management circuit is designed for these three different power generation units to achieve the maximum harvest of magnetic field energy. At the magnetic field of 5.57 Oe, the maximum output power of the three generating units are 0.71 mW (PEH), 1.694 mW (EEH), and 0.27 mW (MEH), respectively. It is experimentally revealed that the proposed hybrid generator can provide a stable power for temperature and humidity sensors integrated with Bluetooth wireless communication technology by harvesting stray magnetic field energy, and has the potential to power wireless sensors. [Display omitted] • The proposed generator includes piezoelectric energy harvesting (PEH), electromagnetic energy harvesting (EEH), and magnetostrictive energy harvesting (MEH). • The power of the generator are 0.71 mW (PEH), 1.694 mW (EEH), and 0.27 mW (MEH), respectively (@5.57 Oe). • The MEH generation unit can also broaden the frequency bandwidth of harvesting magnetic field energy. • The generator successfully drives the low-power sensor, which can be monitored in real-time with a mobile phone. [ABSTRACT FROM AUTHOR]

Epitaxial BiEuFeO (BEFO) thin films are deposited on Nb-doped SrTiO (NSTO) substrates by pulsed laser deposition to fabricate the Pt/BEFO/NSTO (001) heterostructures. These heterostructures possess bipolar resistive switching, where the resistances versus writing voltage exhibits a distinct hysteresis loop and a memristive behavior with good retention and anti-fatigue characteristics. The local resistive switching is confirmed by the conductive atomic force microscopy (C-AFM), suggesting the possibility to scale down the memory cell size. The observed memristive behavior could be attributed to the ferroelectric polarization effect, which modulates the height of potential barrier and width of depletion region at the BEFO/NSTO interface. The continuously tunable resistive switching behavior could be useful to achieve non-volatile, high-density, multilevel random access memory with low energy consumption. [ABSTRACT FROM AUTHOR]

Multilayer Pt/BaTiO 3 /BiFeO 3 /TiO 2 heterostructure was fabricated on FTO substrates by sol-gel technique. This heterostructure shows strong light absorption, sensitive optical switching response, and excellent photovoltaic properties, which are effectively modulated by the ferroelectric polarization. The short circuit current density and open circuit voltage of the multilayer heterostructure are significantly enhanced compared with that of the single layer BiFeO 3 thin film under the initial and positive polarization states. Analysis on the schematic energy band diagrams suggests that the excellent photovoltaic properties can be attributed to the interface Schottky barrier regulated by ferroelectric polarization, in which the TiO 2 layer acts as the electron collection layer, and the ferroelectric BaTiO 3 layer acts as a hole collection layer and also an auxiliary photovoltaic absorption layer to enhance optical absorption properties, thus improve the light absorption efficiency and the separation of electron-hole pairs. These results provide a promising method to optimize the performance of ferroelectric photovoltaic devices by using multilayer heterostructure. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composites are found to be sensitive to both the intensity and the orientation of external magnetic field, therefore, they have been developed as compasses for in-plane AC magnetic field detection. However, the angular sensitivity of ME compasses is still low compared to other compasses, due to their insensitive resonant mode and poor coupling structure. Here, we propose a ME compass working at L-T mode by using a Metglas/PZT composite that integrated with a calibration algorithm. Detection of the intensity and direction of in-plane AC magnetic field is demonstrated synchronously with intensity and angle sensitivities of 0.001 Oe and ± 0.1°, respectively. In addition, when the calibration algorithms are applied, the angular sensitivity is significantly enhanced to ± 0.02°, one order of magnitude higher than that of other reported ME compasses, demonstrating a great potential for applications in magnetic positioning, magnetic field calibration, and other magnetic detection technologies. [Display omitted] • The properties are optimized by theoretical models and finite element analysis, giving a well guidance on similar devices. • A calibration algorithm is proposed, which is able to inexpensively and quickly increase the angular sensitivity. • The device shows intensity and angular sensitivities of 0.001 Oe and ± 0.1°, the latter is improved to ± 0.02° by calibration. [ABSTRACT FROM AUTHOR]