Magneto Resistance Measurement

8/3/2019 Magneto Resistance Measurement

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H. Arul11PHD0036

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Magneto resistance is the property of amaterial to change the value of itselectrical resistance when an externalmagnetic field is applied to it.

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To directly probe the surface electronspin states

To observe current-induced magnetic fielddistribution

To analyze the magneto transportproperties

To measure localized surface magneticfield distribution and surface

topography

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Two current generators and a preamplifierwere attached to a commercially availableAFM system that uses optical deflection forthe detection of cantilever displacement

Current generator I was used to apply aconstant currentto the MR sensor

current generator II was used to applycurrent to the meander-patterned wire

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The design dimensions of the MRcantilever are 200 mm long, 50 mm wide,and 1 mm thick.

The apex of the MR cantilever was usedas an AFM probe to obtain topographicimages of the sample surfaces.

The MR cantilever was tilted at 130 withrespect to the sample surface

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Magnetic fields were induced by a DCcurrent flow in thin film wires and wereobserved using the system.

Current flows in the opposite direction tothe neighbouring lines, the period of themagnetic field distribution induced from the

wire can be expected to be twice as longas that of the topography

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The SV sensor was used to measure themagnetic field strength at a constant heightof 1 mm from the sample surface

The current flow was parallel to the Y-axisand the scan direction was perpendicularto the current flow

The magnetic field distribution can becalculated using BiotSavarts law

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Magneto resistance signal can beconverted into magnetic field using thefollowing equation

V- MR signalS- Sensitivity of spin valued sensorG- Gain of the amplifier

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SG

VH

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Sensor element should be tilted at 13o withrespect to the sample, to maintain uniformfield strength

Noise to signal ratio should be minimizedto attend the uniform field strength

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Optimal data storage densityVibration measurement in MEMS systemsDetecting DNA or protein binding to

capture molecules in a surface layer bymeasuring the stray field from superparamagnetic label particles.

Magneto coupler is a device that usesgiant magneto resistance (GMR) to coupletwo electrical circuits galvanicly isolatedand works from AC down to DC

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T. Takezaki, K. Sueoka /Ultramicroscopy108 (2008) 970974

F. Elhoussine et al. /Journal of Magnetismand Magnetic Materials290-291 (2005)116119

N. Garclia et al./ Journal of Magnetism

and Magnetic Materials240 (2002) 9299Wikipedia.org

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Thank you

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Magneto Resistance Measurement

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