If you have a semiconductor with temperature and current thorugh it fixed, is it possible that the resisitivity changes with the magnetic field, both it decreases or increases?
Dear Francesco,
The answer is yes for a metal. The resistivity is a two tensor and the terms out of the principal diagonal always change due to the magnetic field. But if you have a semiconductor, or one insulator, the resistence depends of the magnetic field only when there are moving charges (by hopping or other mechanisms) under the application of the external electric field. This can be got at higher temperatures if the semiconductor is intrinsic and with low gap, and with doping at larger gaps. But if you have electronic transport you always can get a magnetic dependence for the resistivity or the conductivity.
I would like to refer to a paper published in 1953 ("As some one said, old things are not waste but are really precious"). If the application of a magnetic field would increase the resistivity of a semiconductor, then I assume changing of magnetic field will have the similar effect, however, depending on whether the field is pulsating or it is just swept between positive (+) and negative (-) directions. These are just my two cents.
Article Theory of the Magnetoresistive Effect in Semiconductors
Dear Conrad,
The paper that you references starts its abstract with the paragraph:
Experiments show that the application of a magnetic field increases the resistivity of a semiconductor and produces a decrease in the magnitude of the Hall coefficient. Existing theoretical treatments predict much smaller effects than are actually observed in semiconductors.
Please, could you elaborate a little bit your answer? Changing the magnetic field in time induce an extra electromotive force, while a chang in space induce an extra current.
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