Diamagnetic

Sunday, November 7, 2010

Quartz


a network of SiO4 tetrahedra


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Piezoelectricity

This is the technically most important property of quartz and it has numerous applications. Piezoelectricity was discovered by Jacques and Pierre Curie in 1880, during studies on quartz crystals. When piezoelectric materials are mechanically deformed, their surfaces get electrically charged. The reverse is also true: the same materials will get deformed when put into an electric field. Piezoelectricity is once again an anisotropic property that can be found in certain types of crystals, but not in amorphous substances, and that is dependent on the direction of forces.
The rotational motion due to diamagnetic anisotropy was first reported for large single crystals of quartz and corundum, in the magnetic field where the restoring force of the suspending string became negligible. The suspended crystal rotated gradually with the increasing field, and the diamagnetic principal axis was oriented in the direction parallel to the field. Harmonic oscillations were observed for the crystals in high magnetic field, and the period of oscillation was proportional to the reciprocal of the field. The precise value of diamagnetic anisotropy was obtained from the period of oscillation, and was estimated to be 5.45×10-9 emu/cm3 for quartz and 4.19×10-9 emu/cm3 for corundum.

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