Sensitivity Of Magnetic Field Sensor Research Articles

Strong perpendicular magnetic anisotropy and interlayer coupling in CoRh/Rh/Fe multilayers tailored by Rh spacer layer thickness

Magnetic interlayer coupling is a critical study topic for spintronic device technology because it is an essential component in designing magnetic multilayers with functionality that can be expanded into application areas. Particularly, the interlayer coupling between two ferromagnetic (FM) layers with different magnetic properties in the magnetic field is the specific situation to develop spintronic applications, such as increasing the sensitivity of magnetic field sensors. Therefore, the film structure was chosen as two layers in this study; the first ferromagnetic layer (FM1-CoRh) has a perpendicular and the second ferromagnetic layer (FM2-Fe) has an in-plane (IP) magnetic easy axis in the presence of a magnetic field. Here, a non-magnetic (NM) Rh spacer layer separated the two FM layers. The magnetic properties dependent on spacer layer thickness (t) in CoRh/Rh/Fe multilayers were investigated in detail. It is found that the strength of interlayer coupling alters depending on the t.

Increased sensitivity of spatial filters by combining the magnetic and electrical components of the sensorimotor cortical beta rhythm

Modulation of human magnetic or electrical sensorimotor rhythms during motor imagery is widely used in fundamental and applied neurophysiological research. To date, there is evidence of a better sensitivity of magnetic field sensors to beta-rhythm modulation, however, the potential synergistic effect of combining the two modalities has not yet been investigated. In this study, simultaneous registration of electroencephalogram (EEG) and magnetoencephalogram (MEG) was carried out in eight healthy volunteers during voluntary and imaginary movements, as well as during electrical stimulation of the median nerve. In all subjects, it was possible to identify desynchronization (suppression) of mu and beta rhythms during the performance of sensorimotor tasks, as well as beta synchronization after the end of movement or stimulation. Using the common projections of the covariance matrices of signals of the electric, magnetic, and combined (“MEEG”) modalities, the most sensitive individual spatial filters were calculated separately for each type of reaction. Relative to the pre-stimulus control, the changes in the amplitude of the sensorimotor rhythm components turned out to be the largest in the combined MEEG modality. At the same time, for mu-desynchronization, MEEG turned out to be significantly better than MEG, and for beta-desynchronization, MEEG turned out to be significantly better than both MEG and EEG. For beta synchronization, a shift in the position of sources in the fronto-medial direction was shown, and there were no significant differences in amplitude between modalities. It was also shown that for beta desynchronization, most subjects identified MEG sources with identical EEG projections or without pronounced EEG projections, which indicates the presence of several small tangentially located cortical dipoles involved in beta rhythm desynchronization. The results obtained indicate that in studies of modulation of sensorimotor rhythm components, in particular beta desynchronization, the combination of MEG and EEG leads to greater sensitivity. The multifocal nature of the magnetic beta rhythm and its varying severity in EEG sources indicate the presence of independent regulatory circuits of cortical-thalamic or intracortical origin.

Методы увеличения магнитоэлектрического эффекта в композитных структурах: обзор

The article provides a review of various methods that can be used to increase the magnetoelectric (ME) effect in composite structures based on magnetostrictive and piezoelectric materials. It is shown that the use of adhesive technology and gradient structure, as well as thermal and thermomagnetic treatment of a magnetostrictive amorphous alloy of an ME structure make it possible to achieve a significant increase in the ME effect. To date, great efforts have been made to optimize the strain amplitude in the piezoelectric and magnetostrictive phases of multilayer ME materials. The use of various technologies in the manufacture of ME composites makes it possible, for example, to increase the sensitivity of magnetic field sensors for biomedical applications. Also, an increase in the ME effect opens up great prospects for further research.

Effect of Structure on Sensitivity of Magnetic Field Sensor Based on Non-Adiabatic Tapered Optical Fiber With Magnetic Fluid

Magnetic field sensor based on non-adiabatic tapered optical fiber (NATOF) surrounded with magnetic fluid (MF) has a potential to detect ultra-weak magnetic field. In order to improve the sensitivity of the magnetic field sensor, this paper investigated the effect of structure on sensitivity. The interference occurring between the modes in cladding and MF was analyzed to obtain the relationship between sensitivity and diameter of the tapered waist. Experiments were carried out to verify the proposed relationship. The experiments indicated when the diameter was larger than dispersion turning point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.75 ~\mu \text{m}$ </tex-math></inline-formula> ), the sensitivity of the sensor decreased with the diameter of the tapered waist. The largest sensitivity obtained in the experiment is 6.567 nm/mT under a weak magnetic flux density range from 0 mT to 5 mT. This result is instructive for the manufacture of sensors with specific sensitivity.

A Magnetic Field SPR Sensor Based on Temperature Self-Reference.

In this paper, a novel D-shaped photonic crystal fiber sensor for simultaneous measurements of magnetic field and temperature is proposed and characterized. Based on the surface plasmon resonance theory, the D-shaped flat surface coated with a gold layer is in direct contact with magnetic fluid to detect magnetic field, and one of the relatively small air holes near the fiber core is filled with polydimethylsiloxane (PDMS) to sense temperature. The realization of measuring the magnetic field and temperature separately through two channels depends on the fact that the magnetic field only changes the refractive index of the magnetic fluid, but has no effect on the refractive index of PDMS. The refractive index of the magnetic fluid and PDMS can be affected by temperature at the same time. The sensor designed in this work can separate the variations of the magnetic field and temperature simultaneously, therefore solving the cross-sensitivity problem to further improve the magnetic field sensitivity. When the thickness of the gold film is 50 nm and the radius of the filling hole is 0.52 µm, the magnetic field sensitivity and the temperature sensitivity of magnetic field sensor based on temperature self-reference can reach 0.14274 nm/Oe and −0.229 nm/°C, respectively.

Magnetic shielding of long paraboloid structures in the inhomogeneous magnetic field

Shielding efficacy of the high-temperature superconducting (HTS) magnetic shields depends on the superconductor properties and on the orientation of the external magnetic field. For precise magnetic field measurements in areas with changing direction of magnetic noise it is important to reduce both the parallel and perpendicular components of the magnetic field. We have designed and fabricated magnetic shields of 25 cm long paraboloid shape with closed sides from second-generation HTS tapes. We have characterized HTS shields in DC and variable frequency AC magnetic fields at 77 K above a copper electromagnet acting as the source of inhomogeneous magnetic noise. The HTS magnetic shields reduce the magnetic field noise penetration and enhance the sensitivity of magnetic field sensors. The measurements were performed with the magnetic shield placed between the noise source and the sensor. 2D finite element analysis using Comsol model was generated and the results were compared with the experimental data of magnetic field dependences of the shielding factor (SF).

МЕТОДЫ ВЕРОЯТНОСТНОЙ ОЦЕНКИ ЭФФЕКТИВНОСТИ СРЕДСТВ МОРСКОЙ МАГНИТОМЕТРИИ

Marine magnetometers are promising means of monitoring the water area with an estimated presence of potentially dangerous underwater objects. They are successfully used when searching for underwater objects in conditions of the ineffectiveness of sonar tools: in shallow water, in any media (water, soil) and, especially, at the boundaries of these media. As a rule, the search for an underwater object using magnetometric means is carried out along the “orthogonal tacks” trajectory, the main characteristics of which are the search bandwidth (depending on the magnetic characteristics of the underwater object) and the length of a searching tack. An analysis of the development trends of marine magnetometers revealed the following main directions: the expansion of their functional capabilities, the increase in the sensitivity of magnetic field sensors, and the increase in mass and dimensional characteristics. However, in accordance with modern requirements, the main directions of development of marine magnetometry tools have changed radically. It has been established that the process of detecting an underwater ferromagnetic object by mobile magnetometers is stochastic in nature, which is not taken into account by the traditional method of determining the recommended search band for an underwater object, which leads to the risk of missing it. Therefore, the actual problem of improving search magnetometric means is the development of a methodological apparatus for evaluating the efficiency of detection of underwater objects. A new (probabilistic) approach to the information processing algorithm of the magnetometer signal is proposed, which determines the width of the recommended search band of an object with guaranteed values of the probability characteristics of its detection. The article indicates a problem.

Magneto-optical properties of BiFeO3 thin films using surface plasmon resonance technique

Indigeneously assembled surface plasmon resonance (SPR) set up has been exploited to study the magnetic field dependent optical properties of BiFeO3 thin films. BiFeO3 thin films have been deposited onto gold (Au) coated glass prism by using pulsed laser deposition technique. The surface plasmon modes in prism/Au/BiFeO3/air structure have been excited in Kretschmann configuration at the interface of Au/BiFeO3 thin films. The SPR reflectance curves obtained for prism/Au/BiFeO3/air structure were utilized to investigate the optical properties of BiFeO3 thin films at optical frequency (λ=633nm) as a function of applied magnetic field. SPR curves shows a continuous shift towards lower angles with increasing applied magnetic field, which indicate the promising application of ferromagnetic BiFeO3 film as a magnetic field sensor. Complex dielectric constant of deposited BiFeO3 film was determined by fitting the experimental SPR data with Fresnel׳s equations. The variation of complex dielectric constant and refractive index of BiFeO3 film was studied with increase in magnetic field, and the sensitivity of magnetic field sensor was found to be about 0.52RIU/T.

Specific features of magnetic field penetration into granular superconductors and possible sensitivity of magnetic sensors based on them

The results of experimental and theoretical studies of the magnetic properties of a superconducting ceramic with the composition YBa2Cu3O7 − x are presented. The limiting sensitivity of magnetic field sensors on the basis of a high-temperature superconducting ceramic is discussed.

Influence of bias electric field on magnetoelectric interactions in ferromagnetic-piezoelectric layered structures

The nature of magnetoelectric (ME) interactions has been investigated under a dc electric field E in Ni-lead zirconante titanate bilayer for bending and acoustic modes. Both the ME voltage and the resonance frequencies are sensitively dependent on E and are attributed to variations in the permittivity and piezoelectric coefficient. A 40% increase in the ME voltage and 12% increase in the resonance frequency in comparison to zero bias were observed for bending modes. A similar behavior was observed for ME coupling at acoustic modes. The results are of interest for enhancing the sensitivity of magnetic field sensors based on ME composites.

Influence of surface effects on the sensitivity of magnetic-field sensors

A comparative study of the role of surface effects in the sensitivity of lateral magnetotransistors and magnetodiodes is presented. The surface potential at the Si–SiO2 interface is changed by means of the gate voltage. Both types of devices are realized in standard complementary metal oxide semiconductor technology. The results indicate that improvement of the sensitivity can be achieved in both cases, but the dependence of sensitivity of magnetotransistor on surface effects is much lower than that of magnetodiode.