Ac magnetic susceptibility of the self-doped manganites La0.9−xSr0.1MnO3 (x = 0.02 and 0.03)

The real (χ′) and imaginary (χ″) components of the ac susceptibility of the self-doped manganites La0.9−xSr0.1MnO3 (x = 0.02 and 0.03), have been studied as functions of temperature, ac field amplitude and frequency. Both χ′ and χ″ of the samples are dependent on the ac magnetic field parameters. The influence of magnetic field amplitude and frequency on the ac susceptibility increases by increasing La-vacancy. Increasing La-vacancy, the inhomogeneity of sample increases more, resulting in the formation of strong domain wall pinning centers. The observation of low temperature anomaly and amplitude and frequency dependence of ac susceptibility in the ferromagnetic region is determined mainly by the domain wall dynamics, rather than due to the glassy spin configuration or spin frustration. Activation energy, extracted from Arrhenius-like expression for the frequency and temperature in the experimental ranges could be presented with the following equation: U(H,T)=U01−T/T0H−0.45.