title: The Scanning TMR Microscope for Biosensor Applications.
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.
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. kunalnvyas@gmail.com.
authors: Kunal N
authors: KN
authors: Vyas
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. david.michael.love@gmail.com.
authors: David M
authors: DM
authors: Love
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. ai222@cam.ac.uk.
authors: Adrian
authors: A
authors: Ionescu
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. jl286@cam.ac.uk.
authors: Justin
authors: J
authors: Llandro
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. pk419@cam.ac.uk.
authors: Pratap
authors: P
authors: Kollu
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. tm10007@cam.ac.uk.|Cambridge Biomagnetics Ltd., St John's Innovation Centre, Cowley Road, CB4-0WS Cambridge, UK. tm10007@cam.ac.uk.
authors: Thanos
authors: T
authors: Mitrelias
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. s.holmes@crl.toshiba.co.uk.|Toshiba Research Europe Ltd., Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, CB4-OGZ Cambridge, UK. s.holmes@crl.toshiba.co.uk.
authors: Stuart
authors: S
authors: Holmes
authors: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. chwb101@cam.ac.uk.
authors: Crispin H W
authors: CH
authors: Barnes
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D060526:Magnetic Fields; D016252:Microscopy, Scanning Tunneling / Q000295:instrumentation*