Domains, magnetic field sensors

FIGURE 3.8 Schematic drawing illustrating the remote query nature of the passive, wireless magnetoelastic sensor. Magnetic field pulses, at a frequency near the resonant frequency of the sensor, are generated to vibrate the sensor. The excitation field is then turned off allowing the sensor to continue vibration at its resonant frequency. The transient sensor response is then converted to the frequency domain to extract the resonant information. 

Fig. 5. 3-32 Schematic illustration of an MR read head. A spin valve ( aU-metal or MTJ) is used as an ultrasensitive sensor for the very low magnetic field strength generated by the small magnetic domains (bits). When a weak magnetic field, such as from a bit on a hard disk, passes beneath the read head, the magnetic orientation of the free layer changes its direction relative to the pinned layer, generating a change in electrical resistance due to the GMR effect. (After [3.106])...

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