High-Sensitivity Tunnel Magnetoresistance Sensors Based on Double Indirect and Direct Exchange Coupling Effect*

Abstract Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level, especially for low operating frequency applications. We investigated the transport properties of tunnel magnetoresistance (TMR) sensors based on the double indirect exchange coupling effect. The TMR ratio of about 150% was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved. A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn. Furthermore, the voltage output sensitivity and the noise level of 10.7 mV/V/Oe, 10 nT/Hz1/2 at 1 Hz and 3.3 nT/Hz1/2 at 10 Hz were achieved in Full Wheatstone Bridge configuration. This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.

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A broadband two axis flux-gate magnetometer

Annals of Geophysics ◽

10.4401/ag-4356 ◽

1998 ◽

Vol 41 (3) ◽

Author(s):

P. Palangio

Keyword(s):

Magnetic Field ◽

Low Frequency ◽

High Sensitivity ◽

Magnetic Sensors ◽

Frequency Range ◽

Field Station ◽

Low Weight ◽

Highly Sensitive ◽

Flux Gate ◽

Magnetic Field Variations

A broadband two axis flux-gate magnetometer was developed to obtain high sensitivity in magnetotelluric measurements. In magnetotelluric sounding, natural low frequency electromagnetic fields are used to estimate the conductivity of the Earth's interior. Because variations in the natural magnetic field have small amplitude(10-100 pT) in the frequency range 1 Hz to 100 Hz, highly sensitive magnetic sensors are required. In magnetotelluric measurements two long and heavy solenoids, which must be installed, in the field station, perpendicular to each other (north-south and east-west) and levelled in the horizontal plane are used. The coil is a critical component in magnetotelluric measurements because very slight motions create noise voltages, particularly troublesome in wooded areas; generally the installation takes place in a shallow trench. Moreover the coil records the derivative of the variations rather than the magnetic field variations, consequently the transfer function (amplitude and phase) of this sensor is not constant throughout the frequency range 0.001-100 Hz. The instrument, developed at L'Aquila Geomagnetic Observatory, has a flat response in both amplitude and phase in the frequency band DC-100 Hz, in addition it has low weight, low power, small volume and it is easier to install in the field than induction magnetometers. The sensivity of this magnetometer is 10 pT rms.

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Magnetic-field sensor with self-reference characteristic based on a magnetic fluid and independent plasmonic dual resonances

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.23 ◽

2019 ◽

Vol 10 ◽

pp. 247-255 ◽

Cited By ~ 9

Author(s):

Kun Ren ◽

Xiaobin Ren ◽

Yumeng He ◽

Qun Han

Keyword(s):

Magnetic Field ◽

Refractive Index ◽

Magnetic Fluid ◽

High Sensitivity ◽

Magnetic Sensors ◽

Magnetic Field Sensor ◽

Plasmonic Waveguides ◽

Coupled Mode ◽

Field Sensor ◽

Self Reference

A magnetic-field sensor with self-reference characteristic based on metal–dielectric–metal (MDM) plasmonic waveguides and a magnetic fluid (MF) is proposed and theoretically investigated. Independent dual resonances are supported by the coupled resonator–waveguide system. The physical mechanisms of dual resonances are analyzed by the temporal coupled-mode theory. The transmission response to an external magnetic field is explored by using the remarkable tunability of the refractive index of the MF. Based on the different dependence of two resonances on the external field, a magnetic-field sensor with self-reference characteristic is achieved. The magnetic-field nanosensor shows an excellent performance with a high sensitivity of 27 pm/Oe, i.e., 270 pm/mT. The proposed sensor takes advantage of the refractive-index tunability of the MF and the compactness of the MDM waveguide structure. This research may open new opportunities to design nanoscale magnetic sensors with good performance.

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Amorphous Magnetoelastic Materials

MRS Proceedings ◽

10.1557/proc-360-201 ◽

1994 ◽

Vol 360 ◽

Cited By ~ 2

Author(s):

H. T. Savage ◽

Marilyn Wun-Fogle

Keyword(s):

Magnetic Field ◽

Melt Spinning ◽

High Sensitivity ◽

Low Noise ◽

Tactile Sensors ◽

Magnetic Anisotropy Energy ◽

Magnetic Field Sensors ◽

Crystalline Materials ◽

Magnetoelastic Materials ◽

Very High

AbstractThe outstanding feature of amorphous magnetoelastic alloys is the controllability of the magnetic anisotropy energy, Curie point, magnetostriction and magnetic moment. This control of material characteristics, achieved by magnetic and stress annealing plus changes incomposition, is impossible in crystalline materials. The control allows the design of tactile and magnetic field sensors with special features and very high sensitivity. The materials discussed are prepared by rapid solidification through melt spinning in ribbon and wire geometries and magnetron sputtering onto substrates. As an example of the advantagesof sputtered material, an accelerometer on silicon micro-cantilevers is shown. I-t has nocoils. The basic magnetoelastic theory that governs tactile sensors is shown. Low-noise magnetic field sensors with novel twist anisotropies and Barkhausen instabilities in wiresare discussed.

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Application of polarization ellipse technique for analysis of ULF magnetic fields from two distant stations in Koyna-Warna seismoactive region, West India

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1513-2010 ◽

2010 ◽

Vol 10 (7) ◽

pp. 1513-1522 ◽

Cited By ~ 9

Author(s):

F. Dudkin ◽

B. R. Arora ◽

V. Korepanov ◽

O. Leontyeva ◽

A. K. Sharma ◽

...

Keyword(s):

Magnetic Field ◽

Source Region ◽

Low Frequency ◽

Normal Fault ◽

High Sensitivity ◽

Low Noise ◽

Magnetic Data ◽

Seismic Zone ◽

Electrokinetic Effect ◽

The Magnetic Field

Abstract. A new approach is developed to find the source azimuth of the ultra low frequency (ULF) electromagnetic (EM) signals believed to be emanating from well defined seismic zone. The method is test applied on magnetic data procured from the seismoactive region of Koyna-Warna, known for prolonged reservoir triggered seismicity. Extremely low-noise, high-sensitivity LEMI-30 search coil magnetometers were used to measure simultaneously the vector magnetic field in the frequency range 0.001–32 Hz at two stations, the one located within and another ~100 km away from the seismic active zone. During the observation campaign extending from 15 March to 30 June 2006 two earthquakes (EQs) of magnitude (ML>4) occurred, which are searched for the presence of precursory EM signals. Comparison of polarization ellipses (PE) parameters formed by the magnetic field components at the measurement stations, in select frequency bands, allows discrimination of seismo-EM signals from the natural background ULF signals of magnetospheric/ionospheric origin. The magnetic field components corresponding to spectral bands dominated by seismo-EM fields define the PE plane which at any instant contains the source of the EM fields. Intersection lines of such defined PE planes for distant observation stations clutter in to the source region. Approximating the magnetic-dipole configuration for the source, the magnetic field components along the intersection lines suggest that azimuth of the EM source align in the NNW-SSE direction. This direction well coincides with the orientation of nodal plane of normal fault plane mechanism for the two largest EQs recorded during the campaign. More significantly the correspondence of this direction with the tectonic controlled trend in local seismicity, it has been surmised that high pressure fluid flow along the fault that facilitate EQs in the region may also be the source mechanism for EM fields by electrokinetic effect.

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Serial MTJ-Based TMR Sensors in Bridge Configuration for Detection of Fractured Steel Bar in Magnetic Flux Leakage Testing

Sensors ◽

10.3390/s21020668 ◽

2021 ◽

Vol 21 (2) ◽

pp. 668

Author(s):

Zhenhu Jin ◽

Muhamad Arif Ihsan Mohd Noor Sam ◽

Mikihiko Oogane ◽

Yasuo Ando

Keyword(s):

Magnetic Flux ◽

High Sensitivity ◽

Wheatstone Bridge ◽

Low Noise ◽

Magnetic Flux Leakage ◽

Noise Spectral Density ◽

Steel Bar ◽

Lift Off ◽

Flux Leakage ◽

Magnetic Flux Leakage Testing

Thanks to high sensitivity, excellent scalability, and low power consumption, magnetic tunnel junction (MTJ)-based tunnel magnetoresistance (TMR) sensors have been widely implemented in various industrial fields. In nondestructive magnetic flux leakage testing, the magnetic sensor plays a significant role in the detection results. As highly sensitive sensors, integrated MTJs can suppress frequency-dependent noise and thereby decrease detectivity; therefore, serial MTJ-based sensors allow for the design of high-performance sensors to measure variations in magnetic fields. In the present work, we fabricated serial MTJ-based TMR sensors and connected them to a full Wheatstone bridge circuit. Because noise power can be suppressed by using bridge configuration, the TMR sensor with Wheatstone bridge configuration showed low noise spectral density (0.19 μV/Hz0.5) and excellent detectivity (5.29 × 10−8 Oe/Hz0.5) at a frequency of 1 Hz. Furthermore, in magnetic flux leakage testing, compared with one TMR sensor, the Wheatstone bridge TMR sensors provided a higher signal-to-noise ratio for inspection of a steel bar. The one TMR sensor system could provide a high defect signal due to its high sensitivity at low lift-off (4 cm). However, as a result of its excellent detectivity, the full Wheatstone bridge-based TMR sensor detected the defect even at high lift-off (20 cm). This suggests that the developed TMR sensor provides excellent detectivity, detecting weak field changes in magnetic flux leakage testing.

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Radio Measurements of Coronal Magnetic Fields

International Astronomical Union Colloquium ◽

10.1017/s0252921100024933 ◽

1994 ◽

Vol 144 ◽

pp. 21-28 ◽

Cited By ~ 4

Author(s):

G. B. Gelfreikh

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Solar Corona ◽

Active Regions ◽

High Sensitivity ◽

Coronal Magnetic Field ◽

Transverse Magnetic ◽

Radio Sources ◽

Radio Waves ◽

Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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Magnetic Emission Mapping for Passive Integrated Components Characterisation

ISTFA 2003: Conference Proceedings from the 29th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2003p0440 ◽

2003 ◽

Author(s):

O. Crépel ◽

Y. Bouttement ◽

P. Descamps ◽

C. Goupil ◽

P. Perdu ◽

...

Keyword(s):

Magnetic Field ◽

Mobile Phone ◽

Printed Circuit Board ◽

Magnetic Sensors ◽

Circuit Board ◽

Magnetic Disturbance ◽

Passive Components ◽

Printed Circuit ◽

Integrated Inductor ◽

The Magnetic Field

Abstract We developed a system and a method to characterize the magnetic field induced by circuit board and electronic component, especially integrated inductor, with magnetic sensors. The different magnetic sensors are presented and several applications using this method are discussed. Particularly, in several semiconductor applications (e.g. Mobile phone), active dies are integrated with passive components. To minimize magnetic disturbance, arbitrary margin distances are used. We present a system to characterize precisely the magnetic emission to insure that the margin is sufficient and to reduce the size of the printed circuit board.

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