One familiar example is ordinary window glass, where the atoms or molecules are "stuck"
in random locations (as opposed to a regular crystalline array as
would be found, for example, in ice).
Magnetic systems can be disordered as well. There are several important
kinds of random magnets; within this general area, one of the more
difficult and active areas of research concerns systems known as spin
glasses. These are disordered magnetic systems that contain numerous
internal, conflicting constraints, so that a substantial fraction
cannot be satisfied by any arrangement of the atomic-size magnets
that make up the spin glass. This property is known, not surprisingly,
as "frustration." Spin glasses are thought to be prototypes
for studying macroscopic "frozen-in" (or quenched) disorder
coupled with frustration.
Disordered systems in general present both fundamental scientific
challenges and at the same time hold great promise for applications.
The latter includes not only the possibility of new materials and
devices but also the creation of new algorithms, and applications
to the biological and other sciences.