Linear and nonlinear susceptibilities of samarium manganites

The temperature and field behaviors of the linear and nonlinear responses to a weak ac magnetic field in the Sm1−xSrxMnO3 manganites with x=0.25, 0.3, and 0.4 have been investigated. It is found that the hysteresis of the second harmonic of magnetization in the dc magneticfield arises in the far-paramagnetic range at T≤180 K, whereas the hystereses of the linear susceptibility and the dc resistivity are observed at lower temperatures. This phenomenon is associated with the formation of macroscopic ferromagnetic (ferrimagnetic) domains in the paramagnetic matrix. The shape of the temperature dependence of the linear susceptibility at T>Tc is determined by the degree of doping, and the susceptibility itself nonmonotonically depends on x.