Principles of Magnetoresistive Elements
Magnetoresistive Elements
Semiconductor Materials for Magnetic Sensors
Murata magnetic sensors use magnetoresistive elements made of n-InSb (compound semiconductor of the III-V group).
| Material property |
InSb |
InAs |
GaAs |
Ge |
Si |
| Crystalline structure |
Concentrated zinc ore |
Concentrated zinc ore |
Concentrated zinc ore |
Diamond |
Diamond |
| Band gap (eV) |
0.17 |
0.36 |
1.43 |
0.66 |
1.12 |
| Electron mobility (cm2/V s) |
78000 |
33000 |
8500 |
3900 |
1900 |
| Hole mobility (cm2/V s) |
750 |
450 |
450 |
1900 |
425 |
| Melting point (°C) |
525 |
943 |
1237 |
953 |
1420 |
| Density (Kg/m3) |
5.775 |
5.67 |
5.316 |
5.35 |
2.3 |
Lattice constant ( ) |
6.48 |
6.06 |
5.64 |
5.66 |
5.43 |
| Resistivity (ohm cm) |
5 x 10-3 |
3.1 x 10-1 |
3.8 x 108 |
- |
- |
- n-InSb materials with high electron mobility are used for the magnetoresistive elements.
- InAs, GaAs, Ge, Si, and InSb materials are used for the Hall elements and Hall ICs.
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Structure of the Magnetoresistive Element
The magnetoresistive element has two terminals. The element for practical use is formed like meanders by means of photolithography, so that it has multiple electrodes on the semiconductor surface to provide high resistance and high output.
Element Model (meander-formed element)
- By modifying the shape of the element, a wide range of resistances can be achieved.
- An element is formed on a magnetic or non-magnetic substrate, depending on its usage. If the priority is high output, a magnetic substrate is used. If the priority is immunity to external magnetic noise, a non-magnetic substrate is used.
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Magnetic Flux Density/Resistance Change Characteristic
As expressed by the formula ![Rb = R0 (B/ (0 [1 + m(micro B)2]](images/img_ele_02.gif)
, the resistance increases non-linearly in the range of low magnetic flux densities, while it increases linearly in the range of high magnetic flux densities.
Magnetic Flux Density/Resistance Change Characteristic
- The resistance increases in proportion to the magnetic flux density, independent of the polarity.
- The resistance increases non-linearly in the range of 80mT or less magnetic flux densities. When the magnetic flux density exceeds 80mT, the resistance increases linearly.
- If the magnetic flux density reaches 300mT, it indicates that the resistance has increased approx. four times from the initial resistance.
- The resistance will not be saturated even at a high magnetic flux density.
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Resistance/Temperature Characteristic
The resistance/temperature characteristic depends on the carrier density.
Resistance/Temperature Characteristic
- 100% corresponds to the resistance obtained at 25°C.
- The temperature coefficient is high (approx. -2%/°C).
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Principles of Magnetoresistive Elements
