Synthesis characterization of magnetic properties in La _0.7-xLn_xPb_0.3MnO₃ (Ln=Pr, Nd, Gd, Dy, Sm and Y) perovskite compounds

The magnetization behaviors of perovskite oxides, La_0.7-xLn _xPb_0.3MnO₃ (Ln=Pr, Nd, Gd, Dy, Sm and Y), have been synthesized. The replacement of La ion by Pr, Nd, Gd, Dy, Sm or Y results in a considerable decrease in the ferromagnetic ordering temperature T _c and clearly irreversible behavior in the FC-ZFC curves showing a short-range spin order phase. The fact is in agreement with the smaller ionic radii of Pr, Nd, Gd, Dy, Sm and Y ions in contrast to La ion and the corresponding larger distortion of perovskite structures. The saturation magnetization M_S increases as Pr or Nd content increases while M _S decreases as Sm or Y content increases. Moreover, the saturation magnetization M_S increases and then decreases as Gd and Dy content increases. These results can be explained in terms of the competition between the increase of ferromagnetically interacting spins due to the introduction of magnetic Pr or Sm ions with f-shell electrons and suppression of ferromagnetism due to structure tuning induced by the small ionic radius of the interpolated cation into the La-site.