Note: Detection of a single cobalt microparticle with a microfabricated atomic magnetometer (original) (raw)

Integrated microHall magnetometer to measure the magnetic properties of nanoparticles

Lab on a chip, 2017

Magnetic nanoparticles (MNPs) are widely used in biomedical and clinical applications, including medical imaging, therapeutics, and biological sample processing. Rapid characterization of MNPs, notably their magnetic moments, should facilitate optimization of particle synthesis and accelerate assay development. Here, we report a compact and low-cost magnetometer for fast, on-site MNP characterization. Termed integrated microHall magnetometer (iHM), our device was fabricated using standard semiconductor processes: an array of Hall sensors, transistor switches, and amplifiers were integrated into a single chip, thus improving the detection sensitivity and facilitating chip operation. By applying the iHM, we demonstrate versatile magnetic assays. We measured the magnetic susceptibility and moments of MNPs using small sample amounts (∼10 pL), identified different MNP compositions in mixtures, and detected MNP-labeled single cells.

Application of atomic magnetometry in magnetic particle detection

Applied Physics Letters, 2006

The authors demonstrate the detection of magnetic particles carried by water in a continuous flow using an atomic magnetic gradiometer. Studies on three types of magnetic particles are presented: a single cobalt particle ͑diameter ϳ150 m, multidomain͒, a suspension of superparamagnetic magnetite particles ͑diameter ϳ1 m͒, and ferromagnetic cobalt nanoparticles ͑diameter ϳ10 nm͒. Estimated detection limits are 20 m diameter for a single cobalt particle at a water flow rate of 30 ml/ min, 5 ϫ 10 3 magnetite particles at 160 ml/ min, and 50 pl for the ferromagnetic fluid of cobalt nanoparticles at 130 ml/ min. Possible applications of their method are discussed.

Microfabricated atomic magnetometers and applications

2008

We describe recent work at NIST to develop compact, sensitive atomic magnetometers using a combination of precision optical spectroscopy, atomic physics and techniques of micro-electro-mechanical systems (MEMS). These instruments have sensor head volumes in the range of a few cubic millimeters but are capable of sensing magnetic fields of a few picotesla per root-hertz in the earthpsilas field and as weak as 70 femtotesla per root-hertz in a shielded, low-field environment. We discuss the design, fabrication and testing of several of these devices and propose several applications for which such instruments might be of use.

Microfabricated Atomic Magnetometer

IEEE Sensors, 2005., 2005

Using the techniques of microelectromechanical systems, we are developing chip-scale atomic sensors based on laser excitation of alkali atoms. Recently, we demonstrated a magnetometer physics package based on coherent population trapping that had a sensitivity of 50 pT / Hz 1/2 at 10 Hz, had a volume of 12 mm 3 , and used 195 mW of power [1]. To improve the sensitivity and reduce the power consumption of the magnetometer, we are evaluating other methods of interrogating the atoms for use in microfabricated devices. One of these methods uses frequency modulated nonlinear magneto-optical rotation (FM NMOR). We demonstrate that an FM NMOR magnetometer can be made to self-oscillate, offering simple construction and low power consumption.

High sensitivity magnetization measurements of nanoscale cobalt clusters

Journal of Applied Physics, 1995

Presented is a novel high sensitivity magnetometer allowing us to measure the magnetization reversal of about 104 μB corresponding to a sensitivity of about 10−16 emu. The detector is a niobium micro-bridge DC superconducting quantum interference device (SQUID), fabricated using electron-beam lithography. It is operational in the temperature range of 0–7 K. Furthermore, we present a method to deposit on the SQUID loop a small number of Co clusters of about 2–5 nm in diameter. The first results obtained on these samples show that there is still a ferromagnetic coupling between the clusters and the magnetization reversal takes place by small avalanches.

Microfabricated atomic magnetometers

Optical Magnetometry, 2009

Using the techniques of microelectromechanical systems, we are developing chip-scale atomic sensors based on laser excitation of alkali atoms. Recently, we demonstrated a magnetometer physics package based on coherent population trapping that had a sensitivity of 50 pT / Hz 1/2 at 10 Hz, had a volume of 12 mm 3 , and used 195 mW of power [1]. To improve the sensitivity and reduce the power consumption of the magnetometer, we are evaluating other methods of interrogating the atoms for use in microfabricated devices. One of these methods uses frequency modulated nonlinear magneto-optical rotation (FM NMOR). We demonstrate that an FM NMOR magnetometer can be made to self-oscillate, offering simple construction and low power consumption. I.

Chip Scale Atomic Magnetometers

2006

Using the techniques of microelectromechanical systems, we have constructed a small low-power magnetic sensor based on alkali atoms. We use a coherent population trapping resonance to probe the interaction of the atoms' magnetic moment with a magnetic field, and we detect changes in the magnetic flux density with a sensitivity of 50 pT Hz −1/2 at 10 Hz. The magnetic sensor has a size of 12 mm 3 and dissipates 195 mW of power. Further improvements in size, power dissipation, and magnetic field sensitivity are immediately foreseeable, and such a device could provide a hand-held battery-operated magnetometer with an atom shot-noise limited sensitivity of 0.05 pT Hz −1/2 . Measurement of magnetic fields with picotesla sensitivity is critical to many applications including underground and underwater ordinance detection, 1 geophysical mapping, 2 navigation, and even the detection and mapping of the human heart beat. 3 Sensitive magnetometers often weigh several kilograms, are quite bulky, and dissipate substantial power while operating. In addition, as the sensitivity increases so does the size and power consumption. Large-scale optical magnetometers 4 that use alkali metal vapors achieve sensitivities 5,6 of ϳ1 fT Hz −1/2 , and rival superconducting quantum interference devices 7 in this regard without the need for cryogenic cooling. Depending on the design of an atomoptical magnetometer, it can operate in a magnetic flux density ranging from 10 −15 to Ͼ 10 −3 T. An optical magnetometer measures the absolute field, thereby needing no external calibration, since the measured spin precession frequency of the alkali atom has a known direct relation to the magnetic flux density. By miniaturizing an optical magnetometer based on the coherent population trapping (CPT) effect 8 by a factor of 10 4 , we demonstrate a highly sensitive magnetic sensor that is millimeters in size, and has the potential to enable, for example, long-range remote sensing of magnetic fields based on battery-operated disposable devices.

Chip-scale atomic magnetometer with improved sensitivity by use of the M[sub x] technique

Applied Physics Letters, 2007

The fabrication and performance of a miniature optically pumped atomic magnetometer constructed with microfabricated components are discussed. This device measures the spin precession frequency of 87 Rb atoms to determine the magnetic field by use of the M x technique. It has a demonstrated sensitivity to magnetic fields of 5 pT/ Hz 1/2 for a bandwidth from 1 to 100 Hz, nearly an order of magnitude improvement over our previous chip-scale magnetometer. The 3 dB bandwidth has also been increased to 1 kHz by reconfiguring the miniature vapor cell heater.