Spin-dependent Magnetoresistance Research Articles

Positive magnetoresistance due to impurity interactions in dilute AuCr alloys

The magnetoresistance of dilute AuCr alloys (2.3–322 at.ppm) has been measured in a wide region of temperature (5-3K) and of magnetic field (up to 60 kG). The “modified Kohler's rule” was used to extract the spin dependent magnetoresistance (ϱ M) from measured total magnetoresistance. The results has shown that, except for the most dilute specimen, ϱ M includes explicitly a positive component in addition to the ordinary negative magnetoresistance proportional to log ( H/T). We have attributed this positive ϱ M to the effect of the interactions between the Cr impurities by taking consideration of the generalized phase shift expression of magnetoresistance proposed by Soultie.

Theory of the resonant and non-resonant photoconductivity changes in amorphous silicon

Abstract The resonant and non-resonant photoconductivity changes due to a magnetic field and an additional microwave field are ocnsidered. The effect is shown to bear a close relationship to the anomalous spin-dependent magnetoresistance observed in amorphous semiconductors. It is suggested that a spin-dependent, non-radiative recombination process is responsible for the resonant and non-resonant photo-conductivity changes. Interesting time-dependent effects are found; in particular microwave chopping can turn a quenching line into an enhancing one. The problems associated with exchange-coupled spins are discussed. We compare our results with our recent luminescence results and conclude that the same model can account for both experiments.

Theory of the resonant and non-resonant luminescence changes in amorphous silicon

Abstract The resonant and non-resonant luminescence changes in a-silicon are considered. It is suggested, that the effect is closely related to the anomalous spin-dependent magnetoresistance and photoconductivity changes observed in evaporated and glow-discharge-deposited silicon. The novel feature here is the existence of stable quenching lines. This considerably reduces the choice of recombination models to either a geminate radiative process with singlet-spin memory or to the usual localized-localized recombination process with a spin-dependent, non-radiative transition. The steady-state and time-dependent features of the latter model are analysed. The results are in good agreement with experiment if the exchange interaction between the spins is assumed to be negligibly small. Some interesting and novel time-dependent effects are found and related to recent observations. In particular, it is found that microwave chopping can turn a quenching line into an enhancing one. The problems associated with exch...