Measurements of conduction and magnetic noise of La0.67Ba0.33MnO3 manganite

The temperature dependence of conduction noise and magnetic noise of a bulk sample of La0.67Ba0.33MnO3 (LBMO) manganite was studied. It was observed that normalized conduction noise decreases with a decrease of temperature down to T-c (paramagnetic to ferromagnetic transition temperature). For temperatures T < T-c, the conduction noise showed an increase. The magnetic noise of the LBMO sample was measured by employing a BSCCO rf-SQUID. An enhancement of magnetic noise was observed at paramagnetic to ferromagnetic transition temperature. The frequency spectrum of magnetic flux noise was found to exhibit 1/f(alpha) type behaviour, where alpha = 0.82 +/- 0.04. The analysis of the observed data revealed that enhancement of conduction noise below T-c was not due to the magnetic fluctuations. It could be due to the resistive disorders present in the sample.