Electronic and magnetic properties of (La-Dy)(0.7)Ca0.3MnO3

Electronic and magnetic properties of the perovskitelike compounds of (La1- xDyx)(0.7)Ca0.3MnO3 (0 less than or equal to x less than or equal to 0.5) h ave been studied by measuring electrical resistivity, magnetic susceptibili ty, magnetization, and mag netoresistance. All the compounds except x = 0.5 show a ferromagnetic metal-paramagnetic insulator transition at Tc Te of t he present compounds depend on the tolerance factor t and when t is larger than 0.913 the relations between Te and t are almost the same as those obse rved in the perovskitelike compounds previously examined, which contain rar e-earth metal ions, such as Y3+, Pr3+, and Tb3+. When t is smaller than 0.9 07, a spin glass insulator appears at low temperature. This insulator is di fferent from the ferromagnetic insulator that appears in the compounds cont aining light rare-earth metal ions, such as Pr3+ and/or Y3+, but the same a s that appears in the compound containing heavy ran-earth ions of Tb3+. It has been found that, when t takes a value between 0.907 and 0.913, the reen trant spin-glass state appears. Colossal magnetoresistance and tunneling ma gnetoresistance are clearly observed in the compounds. [S0163-1829(98)00545 -1].