Special magnetic phenomena in heavily doped La0.7-xDyxSr0.3MnO3 system

The magnetism in heavily Dy doped La0.7-x Dy-x Sr0.3MnO3 (0.40 <= x <= 0.70) system is studied in this paper. The M-T relation seems to be complicated with the increase of x. For sample with x = 0.40, AFM behavior exists at T <= T-N and M-T curves under zero field cooling (ZFC) and field cooling (FC) exhibit typical behavior of spincluster glass state above T (N). For the sample with x = 0.50, the M-T curve under ZFC exhibits a valley at a low temperature while the M-T curve under FC exhibits the negative magnetization below T-N. For samples with x = 0.60, 0.70, their ZFC M-T curves are similar to that of x = 0.50, but the FC M-T curves do not exhibit negative values any more. All the peculiar phenomena above are well explained by Neel double-lattice model combined with M-H relation at typical temperatures. The molecular field theory fits well the negative magnetization for x = 0.50.