Mesoscopic phenomena in diluted magnetic semiconductors

This paper reviews recent millikelvin studies of magnetoconductance and noise in nanostructures of a diluted magnetic semiconductor Cd1−xMnxTe. These studies have been particularly rewarding for probing the influence of magnetic ions on mesoscopic transport phenomena. The results demonstrate the existence of a new driving mechanism of the universal conductance fluctuations in magnetic systems. A number of signatures of spin-glass freezing have been observed, such as the appearance of 1/f conductance noise, aging, thermal and magnetic irreversibilities as well as a strong increase in the amplitude of both conductance fluctuations and noise when temperature and the magnetic field are reduced below the freezing line. Statistical analysis of the conductance noise makes it possible to investigate spin dynamics in spin-glass phase and to discriminate between theoretical models. The findings are consistent with the droplet model of spin-glasses.