AG001-01 NVE, AG001-01 Datasheet - Page 80

• Manufacturer Part Number: AG001-01
• Description: KIT ENGINEERING EVALUATION
• Manufacturer: NVE

Specifications of AG001-01

• Rohs Status: RoHS non-compliant
• Sensor Type: Magnetic. GMR (Giant Magnetoresistive)
• Interface: Analog
• Embedded: No
• Utilized Ic / Part: AA & AB Series Analog Sensors
• Voltage - Supply: -
• Sensitivity: -
• Sensing Range: -
• Other names: 391-1003

Application Notes
GMR Material Physics
The giant magnetoresistive phenomenon, discovered in 1988, is an effect found in metallic thin films
consisting of magnetic layers a few nanometers thick separated by equally thin nonmagnetic layers.
Researchers observed a large decrease in the resistance with a magnetic field applied to the films. This
effect is based partly on the increasing resistivity of conductors as their thickness decreases to a few
atomic layers. In bulk material form, conduction electrons in these materials can travel a long distance
before “scattering,” or changing direction, due to a collision with another atomic particle. The average
length that the electron travels before being scattered is called the mean free path length. However, in
materials that are very thin, an electron cannot travel the maximum mean free path length; it is more
likely that the electron will reach the boundary of the material and scatter there, rather than scatter off
another atomic particle. This results in a lower mean free path length for very thin materials. It is
therefore more difficult for conduction electrons to travel in this material, and the result is higher
electrical resistivity. The chart below shows the relationship between resistivity of a magnetic material
such as iron or nickel, and the thickness of the material at very small dimensions. For purposes of
scale, one nanometer equals ten Angstroms; a copper atom has a diameter of about 3 Angstroms:
Resistance of the Material Decreases
Resistivity
as the Mean Free Path Length of
an Electron traveling in the material increases
50
100
150
Mean Free Path Length of an Electron (Angstroms)
In order to take advantage of this effect, GMR films are manufactured with very thin layers of
alternating magnetic and non-magnetic materials. This is done to allow magnetic modulation of the
electron spin in the materials. The spin dependence of conduction electrons in magnetic materials,
along with the increasing resistivity at very small material thicknesses, combine to make the GMR
effect possible.
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