Magnetic Contribution To The Resistivity Noise In A La0.7sr0.3mno3 Film Grain Boundary

Magnetoresistance and resistivity-noise measurements have been performed on a La0.7Sr0.3MnO3 film deposited on a bicrystal substrate with a misorientation angle of 8.2 degrees. The zero field 1/f resistivity noise was investigated at temperatures below the ferromagnetic transition temperature and a detailed study of its field dependence was performed at low temperature, yielding information relating to the magnetic microstructure close to the grain-boundary region. A field dependence of the noise level similar to that of the de resistance is evidenced. The corresponding noise spectra exhibit in addition to the 1/f noise a Lorentzian contribution. This contribution is attributed to thermally activated domain wall motion occurring at fields close to the coercivity. and is connected to the multidomain magnetic state neighboring the grain-boundary region.