An example of a simple device that utilizes pinned domain walls is provided by reference. This experiment consisted of a lithographically defined narrow island connected to the leads via a pair of nanoconstrictions. While the device operated in a diffusive regime the constrictions would pin domain walls, resulting in a giant magnetoresistance signal. When the device operates in a tunnelling regime another magnetoresistance effect is observed, discussed below. A furtherproperty of domain walls is that of current induced domain wall motion. This reversal is believed to occur as a result of the spin-transfer torque exerted by a spin polarized current. It was demonstrated in reference using a lateral device containing three regions which had been patterned to have different coercive fields, allowing the easy formation of a domain wall. The central region was designed to have the lowest coercivity so that the application of current pulses could cause the orientation of the magnetization to be switched. This experiment showed that the current required to achieve this reversal in was two orders of magnitude lower than that of metal systems. It has also been demonstrated that current-induced magnetization reversal can occur across a vertical tunnel junction. Another novel spintronic effect, which was first observed in based tunnel devices, is tunnelling anisotropic magnetoresistance. This effect arises from the intricate dependence of the tunnelling density of states on the magnetization, and can result in magnetoresistance of several orders of magnitude. This was demonstrated first in vertical tunnelling structures and then later in lateral devices. This has established tunnelling anisotropic magnetoresistance as a generic property of ferromagnetic tunnel structures. Similarly, the dependence of the single electron charging energy on the magnetization has resulted in the observation of another dramatic magnetoresistance effect in a device, the so-called Coulomb blockade anisotropic magnetoresistance. References Semiconductor materials Ferromagnetic materials Gallium compounds Arsenides Manganese(III) compounds Zincblende crystal structure