Squid Gradiometers in Real Environments

356

169

The measurement of low-frequency (10−2–103Hz) minute magnetic field variations (10−12Tesla) at room temperature in a passive mode of operation would be critically enabling for deployable neurological signal interfacing and magnetic anomaly detection applications. However, there is presently no magnetic field sensor capable of meeting all of these requirements. Here, we present new bimorph and push-pull magneto-electric laminate composites, which incorporate a charge compensation mechanism (or bridge) that dramatically enhances noise rejection, enabling achievement of such requirements.

Section: -mentioning

confidence: 99%

“…6 The highest sensitivities ͑at 1 Hz͒ of low-temperature ͑T Ͻ 4 K͒ and high-temperature ͑T Ͻ 77 K͒ SQUIDs are about 10 −15 Tesla/ Hz 1/2 ͑Ref. 7͒ and 5 ϫ 10 −14 Tesla/ Hz 1/2 , 8 respectively.…”

mentioning

confidence: 99%

Detection of pico-Tesla magnetic fields using magneto-electric sensors at room temperature

Zhai¹,

Xing²,

Dong³

et al. 2006

356

169

“…There are many types of magnetic sensors: for example, superconducting quantum interference devices 4 or giant magnetoresistance spin valves. 5 However, these sensors require very low operational temperatures ͑liquid nitrogen͒ in order to achieve high sensitivity.…”

mentioning

confidence: 99%

Geomagnetic sensor based on giant magnetoelectric effect

Zhai

Dong

Xing

et al. 2007

Here, the authors report a new type of geomagnetic field sensor based on the giant magnetoelectric effect in Metglas/piezoelectric-fiber laminates that are wrapped with a coil. These sensors can measure quite precisely the value of both the Earth’s magnetic field and its inclination. The geomagnetic field sensor does not require a dc magnetic bias and is driven by a 10mA ac. Highly sensitive dc magnetic field variations of less than 10−9T and angular inclinations of ⩽10−5deg can be detected, potentially offering opportunities for a small global positioning device.

“…Different applications require sensitivity over different bandwidths. For example, magnetic anomaly detectors 13 require sensitivity to frequencies as low as 10 −3 Hz, whereas magnetocardiography 14 and magnetoencephalography 14,15 require high sensitivity between 10 −2 and 10 3 Hz.…”

mentioning

confidence: 99%

Extremely low frequency response of magnetoelectric multilayer composites

Dong

Zhai

Xing

et al. 2005

A promising generation of extremely low frequency magnetic field sensors, based on multilayer composites (MLCs) of magnetostrictive Terfenol-D (Tb1−xDyxFe2−y) and piezoelectric Pb(Mg1∕3Nb2∕3)O3–PbTiO3, has been developed. Our MLC magnetoelectric sensor presently shows a limit in (i) working frequency of ∼5×10−3Hz; and (ii) magnetic field sensitivity of 10−7,10−9, and 10−11T for frequencies of f=10−2, 1, and 102Hz, respectively. The results open up possibilities for sensitive low frequency passive magnetic anomaly detection.