Room-temperature relaxation of the electrical resistance and electrical 1/fα noise observed at very low frequency in the remanent state of glass-ceramics containing magnetite nanoparticles

Slow fluctuations of the electrical resistance R have been systematically observed in three glass-ceramics containing aggregates of magnetite nanoparticles, in measurements where R was studied as a function of time at the magnetic remanence. These fluctuations are shown to be an intrinsic (i.e., not instrumental or spurious) feature of these materials. The associated electrical noise has been obtained by performing a numerical FFT transform of different segments of the R(t) curves after proper baseline subtraction. In this way, the spectral density has been investigated in the very low-frequency region (1×10−3