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

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) have been studied by measuring electrical resistivity, magnetic susceptibility, magnetization, and mag netoresistance. All the compounds except x = 0.5 show a ferromagnetic metal-paramagnetic insulator transition at Tc Te of the 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 observed in the perovskitelike compounds previously examined, which contain rare-earth metal ions, such as Y3+, Pr3+, and Tb3+. When t is smaller than 0.907, a spin glass insulator appears at low temperature. This insulator is different from the ferromagnetic insulator that appears in the compounds containing light rare-earth metal ions, such as Pr3+ and/or Y3+, but the same as 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 reentrant spin-glass state appears. Colossal magnetoresistance and tunneling magnetoresistance are clearly observed in the compounds. [S0163-1829(98)00545-1].