Magnetic Sensor Applications Research Articles

Flexible ceramic composites for Magnetic field sensor Applications

Flexible ceramic composites for Magnetic field sensor Applications

Structural evolution and magnetic, optical, and optoelectronic properties changes in annealed Co0.5Sr0.5Fe2O4 nanoparticles: A comprehensive study

A sample of Co0.5Sr0.5Fe2O4 nanoparticles was synthesized by the coprecipitation technique to explore the effect of annealing on the structure and some physical properties of the produced material. The coprecipitated sample consists of an orthorhombic strontium carbonate phase and the required cubic Co0.5Sr0.5Fe2O4. Annealing at elevated temperatures (900 °C) leads to the formation of cubic and hexagonal phases. This crystal structure was confirmed by X-ray diffraction analysis (XRD). The accuracy of the cation distribution of the cubic phase determined from the Rietveld analysis of XRD patterns is demonstrated by matching the experimental and theoretical lattice constants. There are several noticeable changes in aspects as the annealing temperature goes up. The transmission electron microscopy (TEM) images indicated that heating substantially affects the growth and densification of the smaller nanoparticles. There is a drop in the longitudinal and transverse wave velocities, bulk, rigidity, Young's moduli, Poisson ratio (σ), and Debye temperature (θD) with annealing and grain growth. The saturation magnetization and coercive field are enhanced with annealing. The particle size distribution calculated from TEM is confirmed and supported by the switching field distribution. The indirect optical bandgap energy (Eg) decreased with annealing. The present study concentrated on the thermal treatment impacts on various optical parameters, such as the refractive index and extinction coefficient. The optoelectrical parameters, such as the dielectric constant, dielectric loss, and optical and electrical conductivity, were extensively investigated, giving valuable insights, and their results were interpreted. These findings suggest potential applications in magnetic storage, sensors, and optoelectronics fields.

Exploring the physical properties of Mn2VSi and Mn2VGe Heusler alloys under high pressure conditions: a theoretical investigation using GGA and TB-mBJ calculation

The investigation into Mn2VSi and Mn2VGe Heusler alloys has yielded crucial insights into their structural, mechanical, thermal, electronic, and magnetic attributes. Employing Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) and Tran Blaha modified Becke Johnson (TB-mBJ) method, these alloys were comprehensively analyzed. Structurally, both compounds exhibited stability in the regular Heusler structure, with precise lattice constants and pressure-volume variations. Elastic properties indicated mechanical stability and ductile behavior, with enhanced material strength under elevated pressure. Thermodynamic assessments revealed behavior under extreme conditions, while electronic properties showed half-metallic behavior and semiconducting characteristics. Magnetic moments decreased with pressure, signaling a magnetic transition state in alloys. This theoretical study provides valuable insights into Mn2VSi and Mn2VGe compounds, offering potential applications in spintronics and magnetic sensors.

Effect of Trivalent Ho3+ Ion Doping on Structural, Magnetic, Optical, and Electrical Properties of BiFeO3 Nanoparticles

Holmium (Ho)‐doped bismuth ferrite (BiFeO3) nanoparticles are synthesized using the citrate‐gel autocombustion method to investigate their structural, dielectric, ferroelectric, and magnetic properties. X‐Ray diffraction analysis confirms the formation of a rhombohedral perovskite structure, with crystalline size decreasing from ≈14 to 7 nm as doping levels increase. Fourier‐transform infrared spectroscopy further validates the perovskite phase, while field emission scanning electron microscopy and energy‐dispersive X‐Ray spectroscopy confirm the nanocrystalline nature and composition of the samples. X‐Ray photoelectron spectroscopy verifies the successful incorporation of Ho3+ ions into the BiFeO3 matrix. The dielectric properties show high permittivity and low dielectric losses, while magnetic hysteresis loops reveal enhanced magnetic properties, including increased saturation magnetization, remanence, coercivity, squareness ratio, Bohr magneton, and magnetocrystalline anisotropy. These findings indicate that Ho‐doped BiFeO3 nanoparticles exhibit significantly improved electric and magnetic performance, positioning them as promising candidates for applications in magnetic storage devices and sensors.

Comparative study in magnetic properties of FeCo alloy nanowires and a first-order reversal curve analysis

FeCo alloy nanowires have potential applications in data storage, magnetic sensors and spintronic devices. In this paper, FeCo alloy nanowires with varying diameters were fabricated within an anodic aluminum oxide (AAO) template using electrodeposition method at a constant potential. Characterization of the morphology and structure revealed that the polycrystalline body-center-cubic(bcc) FeCo alloy nanowires were obtained. The influence of diameter of FeCo alloy nanowires on magnetic interaction, domain state and magnetic mechanism was investigated through a first-order reversal curve (FORC) analysis. The findings showed that with an increase in the diameter of FeCo alloy nanowires from 20 nm to 60 nm and 100 nm, the interaction force between the FeCo alloy nanowires increased, the domain state of FeCo alloy nanowires changed from Single Domain (SD) to Multi-Domain (MD), the magnetic reversal mode changed from coherent reversal mode to curling reversal mode.

Enhanced Radiation Efficiency by Resonant Coupling in a Large Bandwidth Magnetoelectric Antenna

AbstractMagnetoelectric (ME) antennas hold the potential for significantly advancing miniaturization in radio frequency devices due to their compact size. However, critical hurdles still remain in ME antennas including low radiation efficiency and narrow bandwidth, which prevent them from seeing widespread use. Here, by sweeping the magnetic field to reach a resonant coupling, a significant enhancement in radiation efficiency by 70.95 ± 6.4% in a broad bandwidth ME antenna with 80 MHz is achieved as well as the far‐field radiation patterns are changed compared with that via non‐resonant coupling. The enhancement depends on the relative orientation between the magnetization and surface acoustic wave propagation direction which is dominated by the symmetry of the driving field induced by shear strain. A larger enhancement occurs when the magnetic field along hard axis of Ni due to the matching helicity and larger strain compared with easy axis scenario. This work demonstrates an innovative methodology that significantly enhances the radiation and reception efficiency in ME antennas, which may provide ideas for subsequent applications in communication antennas and magnetic sensors.

Different exchange bias behavior caused by tuning glassy state in Ni50Mn37Ga13 ribbons

Exchange bias plays a significant role in the application of spin valves and magnetic sensors. A spontaneous exchange bias field of 0.75 kOe can be observed in the annealed Ni50Mn37Ga13 ribbons, while a giant exchange bias field of 6.14 kOe occurs in the quenched samples under field cooling. This is due to the different lattice parameters and microscopic morphology making the annealed and quenched samples, respectively, form superspin glass and spin glass embedded in the antiferromagnetic matrix. The conditions for superspin glass and spin glass to overcome the energy barrier of spin reconfiguration are different, resulting in the difference in exchange bias behavior. This work combines the magnetic properties with the crystal structure and microscopic morphology, providing a method of controlling the glassy state by heat treatments to regulate the exchange bias of Heusler alloys.

Observation of Linear Magnetoresistance in MoO2.

Magnetoresistance, the change in resistance with applied magnetic fields, is crucial to the magnetic sensor technology. Linear magnetoresistance has been intensively studied in semimetals and semiconductors. However, the air-stable oxides with a large linear magnetoresistance are highly desirable but remain to be fully explored. In this paper, we report the direct observation of linear magnetoresistance in polycrystalline MoO2 without any sign of saturation up to 7 T under 50 K. Interestingly, the linear magnetoresistance reaches as large as 1500% under 7 T at 2 K. The linear field dependence is in great contrast to the parabolic behavior observed in single-crystal MoO2, probably due to phonon scattering near the grain boundaries. Our results pave the way to comprehending magneto-transport behavior in oxides and their potential applications in magnetic sensors.

Evidence of self-biased magnetoelectric coupling in eco-friendly (Na0.41K0.09Bi0.5TiO3-Ba0.85Ca0.15Zr0.1Ti0.9O3)-(CoFe2O4) particulate composites

The magnetoelectric (ME) properties of eco-friendly 1-x(0.94Na0.41K0.09Bi0.5TiO3-0.06Ba0.85Ca0.15Zr0.1Ti0.9O3)-x (CoFe2O4) (NKBCZT-CFO) with x = 0, 0.1, 0.2, 0.3 and 0.4 particulate composites were investigated. The X-ray diffraction studies provided evidence for the simultaneous existence of constituent phases (ferroelectric and ferromagnetic) in the composite. The structural and surface morphology analysis of the composite affirmed the homogeneous and densely packed distribution of CFO grains within the NKBCZT matrix. The composite's multiferroic behavior at room temperature was confirmed through the characterization of P vs E and M vs H hysteresis loops. The observed values of remnant polarization (Pr) and coercive field (Ec) are 26.7 μC/cm2 and 35.5 kV/cm, respectively, for 10 mol% of CFO. The increase in CFO content resulted in a decrease in the ferroelectric properties, possibly due to the conductive behaviour exhibited by CFO, and correlated with leakage current measurement. For the composite containing 40 mol% of CFO, the estimated values of remanent (Mr), saturation (Ms) magnetization, coercive field (Hc), and magnetic moment (µB) are 2.35 emu/g, 21.85 emu/g, 104.2 Oe, and 0.86 µB, respectively. The non-Debye type dielectric relaxation processes have been observed in the composites, and the electron hopping mechanism resulted in a higher dielectric constant (εʹ). Enhancement in relaxor nature had been observed through Vogel-Fulcher analysis with CFO content. The evidence of ME coupling was revealed through the direct ME voltage coefficient (αME) and magnetocapacitance (MC) measurement. The observed maximum value of MC measured at 1 kHz for the 20 mol% CFO is ∼5.6 %. Self-biased ME coupling (non-zero αME at HDC = 0 Oe) was observed in 20 and 30 mol% of CFO composite. The highest measured value of αME for 20 and 30 mol% CFO is 3.63 mV/cm.Oe and 4.09 mV/cm.Oe at HDC = 0 Oe respectively. The strong ME interaction and significant value of self-biased ME αME suggest that these composites can be explored for magnetic sensor and ME memory device applications.

Physical Properties of Magnetic Materials of Cobalt Oxide, Iron Oxide and Manganese Oxide

This review focuses on the physical properties of three magnetic materials: Cobalt oxide (Co3O4), Iron oxide (FeO), and Manganese oxide (MnO). These materials exhibit interesting magnetic behavior and have been extensively studied due to their potential applications in various fields, including spintronics, magnetic storage, and magnetic sensors. In this review, we provide a comprehensive overview of the physical properties of Co3O4, FeO, and MnO, including their crystal structures, magnetic properties, structural properties, electrical properties, and thermal Properties. We also discuss the factors influencing the magnetic properties of these materials, such as temperature, doping, and external magnetic fields. Additionally, we highlight the technological applications and challenges associated with these magnetic materials. This review serves as a valuable resource for researchers and scientists interested in understanding and utilizing the physical properties of Co3O4, FeO, and MnO.

Tunable anomalous resistance and large magnetoresistance in HfTe5 by atom doping

The Dirac layered material HfTe5 renews significant interest due to its exotic band structure, leading to abundant transport properties, such as the anomaly resistance peak and its large magnetoresistance. Here, we prepared single crystals HfTe5 and Cr-doped CrxHf1−xTe5 and carried out their electrical transport measurements to explore the underlying physical origin of the anomaly resistance behavior and the large magnetoresistance. An anomalous resistance peak was observed in both intrinsic HfTe5 and the Cr-doped ones. Specifically, the peak temperature in the doped ones experiences an obvious shift from 52 to 34 K as the doping concentration x increases from 0 to 0.15, as well as the magnitude of the peak resistance is significantly enhanced. Furthermore, the magnetoresistance of CrxHf1−xTe5 is reduced by more than one order of magnitude compared with the intrinsic one. The significant reduction in magnetoresistance after Cr doping is attributed to the breaking of the balance between electron and hole carriers, which is confirmed by Kohler's plots. Meanwhile, in the sample where the magnetoresistance was minimized, we observed Shubnikov–de Haas oscillations. These observations illustrate that the large magnetoresistance is primarily contributed by the compensation of electrons and holes rather than the high mobility. Our findings provide valuable insight into how to engineer HfTe5 to achieve large magnetoresistance and its further applications in magnetic sensors and spintronics.

Imaging electromagnetic boundary of microdevice using a wide field quantum microscope.

Imaging of electronic device surface or sub-surface electromagnetic fields under operating conditions is important for device design and diagnosis. In this study, we proposed a method to characterize specific magnetic field properties of electromagnetic devices at micron-scale using a solid-state quantum sensor, namely diamond nitrogen-vacancy (NV) centers. By employing a wide-field magnetic field measurement technique based on NV centers, we rapidly obtain the first-order magnetic field distribution of anomalous regions. Furthermore, we approximate the second-order magnetic field (magnetic gradient tensor) using the differential gradient method. To visualize the electromagnetic anomalous regions boundary, we utilize the tensor invariants of the magnetic gradient tensor components, along with their nonlinear combinations. The identification error rate of the anomalous regions is within 12.5%. Additionally, the electromagnetic field of anomalous regions is simulated showing the measurement accuracy. Our study shows that the experimental results are very similar to the theoretical simulation of the electromagnetic field (error: 7%). This work is essential for advancing electromagnetic field characterization of electronic devices and the advancement of quantum magnetic sensor applications.

Perspective on nanoscale magnetic sensors using giant anomalous Hall effect in topological magnetic materials for read head application in magnetic recording

Recent advances in the study of materials with topological electronic band structures have revealed magnetic materials exhibiting giant anomalous Hall effects (AHEs). The giant AHE has not only attracted the research interest in its mechanism but also opened up the possibility of practical application in magnetic sensors. In this article, we describe simulation-based investigations of AHE magnetic sensors for applications to read head sensors (readers) of hard disk drives. With the shrinking of magnetic recording patterns, the reader technology, which currently uses multilayer-based tunnel magnetoresistance (TMR) devices, is associated with fundamental challenges, such as insufficient spatial resolution and signal-to-noise ratio (SNR) in sensors with dimensions below 20 nm. The structure of an AHE-based device composed of a single ferromagnetic material is advantageous for magnetic sensors with nanoscale dimensions. We found that AHE readers using topological ferromagnets with giant AHE, such as Co2MnGa, can achieve a higher SNR than current TMR readers. The higher SNR originates from the large output signal of the giant AHE as well as from the reduced thermal magnetic noise, which is the dominant noise in TMR readers. We highlight a major challenge in the development of AHE readers: the reduction in the output signal due to the shunting of the bias current and the leakage of the Hall voltage through the soft magnetic shields surrounding the AHE reader. We propose reader structures that overcome this challenge. Finally, we discuss the scope for future research to realize AHE readers.

First-principles study on the adsorption and sensing properties of methyl acetate on VTe2 doped systems (Ti, Sc, Ru, Y).

Transition metal dichalcogenide (TMD) sensors feature a large surface-to-volume ratio, high sensitivity, fast response time, and low energy consumption. Among these materials, VTe2, with its spin polarization, shows potential as a magnetic sensor. This study aims to provide theoretical guidance for the development of methyl acetate sensors by investigating the stability and electronic properties of metal-doped VTe2 systems (Ti, Sc, Ru, and Y) using ab initio molecular dynamics (AIMD) simulations at 300 K and density functional theory (DFT) calculations. The results indicate that the doping system can be stable at 300 K. Doping VTe2 enhances spin polarization, increases the overall magnetic moment of the system, and maintains good conductivity. This suggests its potential for use in magnetic sensor applications. Among these systems, Ti-, Sc-, and Y-doped surfaces exhibited chemical adsorption, while the Ru-doped surface showed physical adsorption. Additionally, molecular dynamics simulations conducted over 5000 fs at 800 K showed that methyl acetate desorbs from the sensor surface, confirming its recyclability. These results highlight the excellent electrical and magnetic properties of the VTe2 doped system, making it a promising candidate for the design of methyl acetate sensors.

Synthesis and characterization of magnetoelectric Ba2Zn2Fe12O22–PbZr0.52Ti0.48O3 electrospun core–shell nanofibers for the AC/DC magnetic field sensor application

Synthesis and characterization of magnetoelectric Ba2Zn2Fe12O22–PbZr0.52Ti0.48O3 electrospun core–shell nanofibers for the AC/DC magnetic field sensor application

Multi-pole magnetization of NdFeB magnetic elastomers via a programmable magnetic stamp inspired by movable type printing

Multi-pole magnetization is crucial for enhancing the magnetic field strength of magnetic films. Programmable multi-pole magnetization with adjustable pole pitch and covering thicknesses from submillimeter to millimeter are challenging tasks. This paper introduces a programmable magnetic stamp method inspired by movable printing. Demagnetization curves at various temperatures illustrate that NdFeB has lower coercivity when heated, making it easier to magnetize. SmCo magnets as high temperature resistant magnetic stamps provide enough external magnetic field. Heating transfers the magnetic pole distribution of magnetic stamps to the NdFeB film. Using this method, we magnetize the NdFeB magnetic film with a checkerboard pattern (interlaced N and S poles). The minimum width of the pole pitch is 1.3 mm. Comparing the measured magnetic field results with the simulation values of ANSYS Maxwell, the trends are relatively close. Furthermore, we investigate the magnetic field component (Bz) related to height and compare the differences between direct and reverse magnetization. Additionally, five magnetic patterns are customized using arranged SmCo magnet arrays. Notably, this study accomplishes multi-pole magnetization with up to 100 poles, covering a magnetic film thickness ranging from 100 µm to 1 mm. The proposed approach provides submillimeter/millimeter-thick NdFeB magnetic films that work as powerful flux sources and exhibit promising applications in magnetic tactile sensors and soft robots.

Highly ordered single domain Fe2-xCo1+xGa (0 ≤ x ≤ 1) nanoparticles synthesized by a template-less chemical route

A comprehensive study has been carried out on chemically synthesized Fe2-xCo1+xGa (0 ≤ x ≤ 1) nanoparticles using both experimental and theoretical tools. Adoption of a template-free preparation route ensured impurity-free and phase-pure Heusler alloy nanoparticles. Depending on the composition, these nanoparticles exhibit highly ordered L21 or X type Heusler alloy structure. These nanoparticles have high saturation magnetization (3.90 – 5.15 µB/f.u.), high Curie temperature (≥ 1100 K) and high effective anisotropy constant (∼ 106 erg/cc) along with low coercive field (≤ 12 Oe) and low remnant magnetization (≤ 0.03 µB/f.u.). Emergence of superparamagnetism in these single (magnetic) domain nanoparticles is another interesting aspect. The electronic density of states of these alloys near Fermi level have also been evaluated as a function of composition using ab initio calculations. These results indicate Fe2-xCo1+xGa nanoparticles to be promising candidates for high density magnetic media and nanomagnetic sensor applications.

Switchable phase transitions from non-magnetic to magnetic cerium oxide nanoparticles using acoustic shock waves

In the present framework, we report a reversible magnetic phase transition that occurs from a mixed diamagnetic (nonmagnetic) state to a weak ferromagnetic (magnetic) state exhibited by cerium oxide nanoparticles (CeO2 NPs) under shocked conditions wherein the magnetic phase transitions are observed to be switchable phase transitions of mixed diamagnetic - weak ferromagnetic - mixed diamagnetic - weak ferromagnetic for the respective shock pulses of 0, 50, 100 and 150, which is probably reported for the first time, and the observed values of the saturation magnetization are 0.9117, 0.1022, 0.8783 and 3.7780 emu/g, respectively. The possible reasons behind the observed reversible magnetic phase transition are proposed by the outcomes attained from the spectroscopic and microscopic techniques. Based on the obtained analytical results, it is confirmed that the observed room temperature weak ferromagnetism is because of the enhancement of Ce3+ ions (reduction of Ce4+ ions) and oxygen vacancies such that the title material is suggested for the applications of magnetic sensors.

A Flexible Magnetic Field Sensor Based on PZT/CFO Bilayer via van der Waals Oxide Heteroepitaxy.

Magnetoelectric (ME) magnetic field sensors utilize ME effects in ferroelectric ferromagnetic layered heterostructures to convert magnetic signals into electrical signals. However, the substrate clamping effect greatly limits the design and fabrication of ME composites with high ME coefficients. To reduce the clamping effect and improve the ME response, a flexible ME sensor based on PbZr0.2Ti0.8O3 (PZT)/CoFe2O4 (CFO) ME bilayered heterostructure was deposited on mica substrates via van der Waals oxide heteroepitaxy. A saturated magnetization of 114.5 emu/cm3 was observed in the bilayers. The flexible sensor exhibited a strong ME coefficient of 6.12 V/cm·Oe. The local ME coupling has been confirmed by the evolution of the ferroelectric domain under applied magnetic fields. The flexible ME sensor possessed a stable response with high sensitivity to both AC and DC weak magnetic fields. A high linearity of 0.9988 and sensitivity of 72.65 mV/Oe of the ME sensor were obtained under flat states. The ME output and limit-of-detection under different bending states showed an inferior trend as the bending radius increased. A flexible proximity sensor has been demonstrated, indicating a promising avenue for wearable device applications and significantly broadening the potential application of the flexible ME magnetic field sensors.

Review on application of magnetic current sensor in condition monitoring of power transmission and transformation equipment

Review on application of magnetic current sensor in condition monitoring of power transmission and transformation equipment