1/F Noise In Patterned La2/3sr1/3mno3 Thin Films In The 300-400 K Range

Detailed investigations of 1/f electrical noise were performed in bridges of various widths and lengths patterned in La2/3Sr1/3MnO3 (LSMO) thin films deposited on SrTiO3 (001) substrates. The measurements were analyzed in the framework of the semiempirical Hooge relation, which routinely enables the evaluation of noise level in materials of different compositions, sizes and in different bias conditions. A review of published data on noise in manganites is first given. Our measurement setup is briefly described, pointing out the possible parasitic external noise sources. As expected, the quadratic dependence of the noise power voltage spectral density versus applied voltage was verified in all the measured bridges. However, the normalized Hooge parameter (alpha(H)/n) has been surprisingly found width dependent, and this dependence remained in all the investigated temperature range of 300-400 K. Open questions arise to determine whether the use of the semiempirical Hooge relation is valid in these LSMO thin films, especially in a temperature range close to their phase transition. The effective volume might be different from the geometrical volume indeed. We finally measured alpha(H)/n of 8x10(-31) m(3) at 300 K, which is among the lowest values reported for LSMO thin films and of the order of noise level in conventional metals. (C) 2008 American Institute of Physics.