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The Scanning TMR Microscope for Biosensor Applications.

Vyas KN, Love DM, Ionescu A, Llandro J, Kollu P, Mitrelias T, Holmes S, Barnes CH - Biosensors (Basel) (2015)

Bottom Line: We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D.By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe.By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance.

View Article: PubMed Central - PubMed

Affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. kunalnvyas@gmail.com.

ABSTRACT
We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D. By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance. The modular design, incorporating a TMR sensor with an optical microscope, renders this set-up a versatile platform for studying and imaging immobilised magnetic carriers and barcodes currently employed in biosensor platforms, magnetotactic bacteria and other complex magnetic domain structures of micron-sized entities. The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

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The data obtained when scanning a TMR sensor a few microns below a three-bit tag with equal aspect ratios (1:2.5) and thereby measuring the stray field in a 50 × 90 µm2 area. The sensitive axis is vertical as presented in the figure. The images are obtained from the real component (x), the amplitude (R) and the phase (θ) of the signal. Frequency: 233 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
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biosensors-05-00172-f007: The data obtained when scanning a TMR sensor a few microns below a three-bit tag with equal aspect ratios (1:2.5) and thereby measuring the stray field in a 50 × 90 µm2 area. The sensitive axis is vertical as presented in the figure. The images are obtained from the real component (x), the amplitude (R) and the phase (θ) of the signal. Frequency: 233 Hz, time-constant: 50 ms, scan speed: 40 µm/s.

Mentions: Figure 7 shows the images obtained when scanning a three-bit magnetic tag. The real component (x) of the impedance of the sensor contains information about both the amplitude and the sign of the magnetic field in the sensitive direction, which is along the length of the elements, as seen in the figure. Although one can make out that there must be a domain breakdown, it is difficult to discern the underpinning structure. This structure is much more apparent, if we display the data using the amplitude, R, and phase, θ.


The Scanning TMR Microscope for Biosensor Applications.

Vyas KN, Love DM, Ionescu A, Llandro J, Kollu P, Mitrelias T, Holmes S, Barnes CH - Biosensors (Basel) (2015)

The data obtained when scanning a TMR sensor a few microns below a three-bit tag with equal aspect ratios (1:2.5) and thereby measuring the stray field in a 50 × 90 µm2 area. The sensitive axis is vertical as presented in the figure. The images are obtained from the real component (x), the amplitude (R) and the phase (θ) of the signal. Frequency: 233 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493544&req=5

biosensors-05-00172-f007: The data obtained when scanning a TMR sensor a few microns below a three-bit tag with equal aspect ratios (1:2.5) and thereby measuring the stray field in a 50 × 90 µm2 area. The sensitive axis is vertical as presented in the figure. The images are obtained from the real component (x), the amplitude (R) and the phase (θ) of the signal. Frequency: 233 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
Mentions: Figure 7 shows the images obtained when scanning a three-bit magnetic tag. The real component (x) of the impedance of the sensor contains information about both the amplitude and the sign of the magnetic field in the sensitive direction, which is along the length of the elements, as seen in the figure. Although one can make out that there must be a domain breakdown, it is difficult to discern the underpinning structure. This structure is much more apparent, if we display the data using the amplitude, R, and phase, θ.

Bottom Line: We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D.By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe.By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance.

View Article: PubMed Central - PubMed

Affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. kunalnvyas@gmail.com.

ABSTRACT
We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D. By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance. The modular design, incorporating a TMR sensor with an optical microscope, renders this set-up a versatile platform for studying and imaging immobilised magnetic carriers and barcodes currently employed in biosensor platforms, magnetotactic bacteria and other complex magnetic domain structures of micron-sized entities. The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

Show MeSH
Related in: MedlinePlus