Current noise in some transition-metal compounds

Abstract

Measurements are reported on current noise in some single crystals of transition-metal compounds, namely: reduced Al-doped rutile (TiO2), Li-doped NiO, Li-doped CoO and Ga-doped CdCr2Se4. Also results obtained with polycrystalline Ga-doped CdCr2Se4 are reported. The current-noise spectra of the materials mentioned above showed flicker noise with a frequency dependence of 1/fβ, where the value of β is in the range 0.7 to 1.2. The magnitude of the flicker noise is compared with a phenomenological formula for flicker noise in semiconductors and metals. It turned out that the magnitude of the current noise in reduced rutile is smaller by a factor 103 than predicted by the phenomenological formula.