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Giant magnetoresistance (GMR) sensors have been widely used in current detection, compass, automobile, and Internet of Things. The linearity of GMR sensors relies on a magnetic annealing process above the blocking temperature of the antiferromagnetic layer, which causes the same magnetization directions in the free and pinned ferromagnetic layers. Here we construct an orthogonal magnetic anisotropic structure by using a relatively low annealing temperature of 145 °C, where the magnetization direction of the free layer is perpendicular to that of the pinned layer so that a linear output can be realized. Quantitative magneto-optical kerr microscope (MOKE) is used to investigate the vector distribution of the magnetic domains, showing that an orthogonal anisotropy is established by the low temperature annealing process. GMR magnetic field sensor with a sensitivity of 0.78 mV/V/Oe and a measurement range of -20 to 20 Oe is demonstrated, which provides an effective method to enhance the linearity of the magnetic sensors with spin valve structures.

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.

Electric field (E-field) control of magnetism based on magnetoelectric coupling is one of the promising approaches for manipulating the magnetization with low power consumption. The evolution of magnetic domains under in-situ E-fields is significant for the practical applications in integrated micro/nano devices. Here, we report the vector analysis of the E-field-driven antiparallel magnetic domain evolution in FeCoSiB/PMN-PT(011) multiferroic heterostructures via in-situ quantitative magneto-optical Kerr microscope. It is demonstrated that the magnetic domains can be switched to both the 0° and 180° easy directions at the same time by E-fields, resulting in antiparallel magnetization distribution in ferromagnetic/ferroelectric heterostructures. This antiparallel magnetic domain evolution is attributed to energy minimization with the uniaxial strains by E-fields which can induce the rotation of domains no more than 90°. Moreover, domains can be driven along only one or both easy axis directions by reasonably selecting the initial magnetic domain distribution. The vector analysis of magnetic domain evolution can provide visual insights into the strain-mediated magnetoelectric effect, and promote the fundamental understanding of electrical regulation of magnetism.

Exchange bias between ferromagnetic and antiferromagnetic layers has been widely utilized in spintronic devices. Controlling the exchange bias in magnetic multilayers by an electric field (E-field) has been proposed as a low-power solution for manipulating the macroscopic properties such as exchange bias fields and magnetization values, while how the magnetic domains respond to the E-fields has rarely been reported in an exchange-biased system. Here, we realize the vector imaging of reversible electrical modulation of magnetization reversal in exchange-biased CoFeB/IrMn/PMN-PT (011) multiferroic heterostructures, utilizing in-situ quantitative magneto-optical Kerr effect (MOKE) microscopy. Under the electrical control, magnetic domains at −80 Oe rotate reversibly between around 160° and 80°–120°, whose transverse components reverse from 225° to 45° correspondingly. Moreover, pixel-by-pixel comparisons are conducted to further imply the reversible magnetization reversal by E-fields. E-field-induced reversible magnetization reversal is also demonstrated without applying external magnetic fields. Vector imaging of electrical manipulation of exchange bias is of great significance in understanding the magnetoelectric effect and the development of next-generation spintronic devices.

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.

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.

Magnetoelectric (ME) composites exhibit high sensitivity for detecting the strength of weak magnetic field. Yet, they are not sensitive to the angle of a randomly orientated in-plane ac magnetic field, since the strain-mediated ME structures merely response to magnetic field along certain direction. In this article, an ME compass for detecting the intensity as well as the orientation of in-plane ac magnetic field is proposed. The ME compass is designed with the barbell-shaped structure, where NdFeB permanent magnets induce compressive stress on piezoelectric components via torque effect, so that the magneto-mechano-electric coupling effect is mediated by stress without dc magnetic bias field. The ME compass reveals a low resonant frequency ( d 33 piezoelectric coefficient is dominant to the ME effect of the compass, with an ME coefficient of 0.7302 V/cm Oe at resonance. The proposed device presents excellent performance for detecting in-plane ac magnetic field with arbitrary direction, where the sensitivities for intensity and angle are 0.01 Oe and ±0.2°, respectively. Additionally, the barbell-shaped structure brings advantages, such as simple construction, stable performance, and durability, indicating promising applications in angular sensors and compasses.

Piezoelectric ceramics exhibit three conventional piezoelectric coefficients, i.e., d33, d31, d15, due to their ∞ m m crystal symmetry. Unconventional piezoelectric coefficients, such as d11, d12, d13, d14, d16, etc., can only be extracted from piezoelectric single crystals of special symmetry with specific cut direction. Here we demonstrate a rotated poling method to realize unconventional piezoelectric coefficients in perovskite piezoelectric ceramics. This method is elaborated in theory and experimentally proven to be effective. Full nonzero piezoelectric coefficients in the 3 × 6 piezoelectric coefficients matrix can be obtained by combining these “quasi (effective) piezoelectric coefficients” with the conventional piezoelectric coefficients, which would expand applications in a wide variety of piezoelectric devices.

Magnetic field sensors based on the strain-mediated magnetoelectric (ME) coupling are usually bulky and energy-consuming due to the requirement for DC magnetic bias field, and the use of piezoelectric ceramics or single crystals cannot bear overlarge strain due to their fragility. Here, we demonstrate a stress-mediated ME sensor operating in torque mode without magnetic bias field. Combined with elastic layers, the NdFeB permanent magnets induce compressive stress on the piezoelectric layer via torque effect under a weak magnetic field. The contribution from d33 piezoelectric coefficient is dominant to the ME effect, and a large ME voltage of 2480 mV is observed at 13.6 Oe. At the resonate frequency of 138.7 Hz, magnetoelectric coefficient is found to be as high as 6.08 V/cm Oe. Our results reveal that the proposed ME sensor mediated by stress is excellent in performance and reliable in durability, which is promising for magnetic sensor applications.

Magnetoelectric (ME) composites of bulk structures show strong ME coupling performance, and thus magnetoelectric bulk composites and their related devices have been attracting increasing attention over the last few years. Two kinds of ME coupling mechanisms can be found in ME bulk composites, i.e., direct ME coupling and converse ME coupling, where electric field control of magnetization or magnetic field control of ferroelectric polarization can be achieved. Then, ultra-fast, low-power, and miniaturized electronics can be developed based on the novel functionalities of both direct and converse ME coupling effects. Direct ME coupling is used in devices such as ME sensors and energy harvesters, while converse ME coupling is used in voltage tunable inductors, bandstop filters, ME antennas, tunable resonators, etc. Here, we present a review of bulk structure ME composite materials, as well as some notable potential applications of ME composites, with emphasis on both the opportunities and challenges for the application of ME composites. The performance of ME bulk composites, their coupling structures, state-of-the-art device applications, and perspectives on direct (magnetic to electric) and converse (electric to magnetic) ME devices are summarized.

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.

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.

Realization of novel topological phases in magnonic band structures represents a new opportunity for the development of spintronics and magnonics with low power consumption. In this work, we show that in antiparallelly aligned magnetic multilayers, the long-range, chiral dipolar interaction between propagating magnons generates bulk bands with nonzero Chern integers and magnonic surface states carrying chiral spin currents. The surface states are highly localized and can be easily toggled between nontrivial and trivial phases through an external magnetic field. The realization of chiral surface spin currents in this dipolarly coupled heterostructure represents a magnonic implementation of the coupled wire model that has been extensively explored in electronic systems. Our work presents an easy-to-implement system for realizing topological magnonic surface states and low-dissipation spin current transport in a tunable manner.

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

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 Ni0.81Fe0.19 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]-/Ni0.81Fe0.19 (2.5 nm)/Ta heterostructure via ILG caused electrostatic doping. This is evidenced in situ reversible ferromagnetic field (Hr) 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.

Piezoelectric devices based on d36 mode are remarkably stable that depolarization rarely occurs in d36 face shear mode, because d36 mode is completely different from d15 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., d33, d31, and d15), while d36 only exists in single crystals of specific point groups and cut directions. In this work, we propose a method to realize d36 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 d36 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 d36 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.

Ferroelectric resistive switching has recently attracted considerable attention as a promising candidate for next-generation non-volatile memory. In this work, we report an electro and photon double-driven bipolar resistive switching behavior in Pt /Bi0.9Eu0.1FeO3 (BEFO) /Nb-doped SrTiO3 (NSTO) heterostructures prepared via pulsed laser deposition. In addition to the polarization-based control of the resistive memory, a switchable photovoltaic effect is observed that can be used to detect the polarization direction non-destructively. Significantly, the electric field-modulated interfacial barrier can be further affected by photon-generated carriers. This phenomenon is attributed to the barrier modulation in the Pt /BEFO and BEFO /NSTO interfaces by electric field and photon excitation. These results indicate the feasibility of non-volatile and non-destructive readout from ferroelectric memory.

The operation mechanism of giant magnetoresistance (GMR) sensors relies on the linear response of the magnetization direction to an external magnetic field. Since the magnetic anisotropy of ferromagnetic layers can be manipulated by a strain-mediated magnetoelectric coupling effect, we propose a tunable GMR magnetic field sensor design that allows for voltage tuning of the linear range and sensitivity. A spin valve structure Ru/CoFe/Cu/CoFe/IrMn/Ru is grown on a PMN-PT (011) substrate, and the magnetization directions of ferromagnetic layers can be controlled by an electric field. An adjustable linear magnetoresistance is therefore induced. Based on the magnetoelectric coupling effect and spin valve, we prepared tunable GMR magnetic field sensors with bridge structures. The linear sensing range of a DC magnetic field is enhanced 6 times by applying an electric field of 14 kV/cm. The electrically tunable GMR sensor fulfills the requirements to work at different magnetic field ranges in the same configuration, therefore exhibiting great potential for applications in the Internet of things.

The tunable range of RF/microwave devices is limited not only due to the difficulty in growing high-quality magnetic oxide thin films but also because of their low magnetostrictive coefficient as in Y3Fe5O12 (YIG) thin films. In this work, we have fabricated flexible YIG thin films by using pulsed laser deposition (PLD) technology, which exhibit a low-damping constant (2.67 × 10−4) and well-established magnetic properties suitable for RF/microwave materials. A noticeable ferromagnetic resonance (FMR) field shift of 180 Oe was obtained along the out-of-plane direction via a flexible tunable factor f(R), which results in a frequency shift as high as 550 MHz. The result shows a greater FMR tuning than that induced by ferroelectric single crystals. At the same time, a systematic theoretical framework for tuning FMR characteristics was presented for the flexible YIG/mica thin films, which would provide an effective tuning method for other flexible magnetic oxides with low magnetostrictive coefficients. Last but not least, a flexible coplanar waveguide (CPW) integrated with the flexible YIG thin films shows excellent microwave magnetic stability and fatigue-resistant behavior. It would open a new door for further applications, such as flexible spiral detectors and high-frequency signal processors in the near future.

A single device with extensive new functionality is highly attractive for the increasing demands for complex and multifunctional optoelectronics. Multi-field coupling has been drawing considerable attention because it leads to materials that can be simultaneously operated under several external stimuli (e.g. magnetic field, electric field, electric current, light, strain, etc.), which allows each unit to store multiple bits of information and thus enhance the memory density. In this work, we report an electro–opto–mechano-driven reversible multi-state memory device based on photocurrent in Bi0.9Eu0.1FeO3 (BEFO)/La0.67Sr0.33MnO3 (LSMO)/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) heterostructures. It is found that the short-circuit current density (Jsc) can be switched by the variation of the potential barrier height and depletion region width at the Pt/BEFO interface modulated by light illumination, external strain, and ferroelectric polarization reversal. This work opens up pathways toward the emergence of novel device design features with dynamic control for developing high-performance electric–optical–mechanism integrated devices based on the BiFeO3-based heterostructures.

ITO/BNT/Pt heterojunction structure has been prepared by sol-gel method combined with dc magnetron sputtering. The BNT (Bi3.15Nd0.85Ti3O12) films were polycrystalline with typical ferroelectric hys...