Bias Exponent of Resistance Noise as a Probe for Disordered Systems

The power spectral density S v ( f ) of voltage fluctuations in the Ohmic regime of a system varies with voltage V as S v ( f ) ≈  V β where β is the bias exponent. The equilibrium resistance fluctuation in a homogeneous system provides β =  2 but in disordered systems, we show that β strongly depends on quenched disorder and temperature and is less than 2 in the Ohmic region. At a fixed temperature, β remains nearly equal to 2 at low disorder and decreases from 2 to 1 with the increase in disorder. Interestingly, similar variation in β is observed with the change in temperature from high to low at a fixed quenched disorder. These two cases favor weak localization in the limit of high disorder or low temperature. Experimental results on manganite compounds indicate that the bias exponent β could be used as a sensible nondestructive parameter to identify the existence of a phase transition evolved during the course of investigation. Remarkable correlations between the electrical transport and the power spectral density S v ( f ) are observed and explained with the help of inhomogeneous distribution of currents. The results are also supported by the non‐Gaussian nature of the second spectrum of 1/ f noise at different temperatures.