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

Abstract

Electronic and magnetic properties of the perovskitelike compounds of $\left({\mathrm{La}}_{1-x}{\mathrm{Dy}}_x{)}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_3\hspace{0.5em}\right(0\mathrm{}<~x<~0.5)$ have been studied by measuring electrical resistivity, magnetic susceptibility, magnetization, and magnetoresistance. All the compounds except $x=0.5\mathrm{}$ show a ferromagnetic metal-paramagnetic insulator transition at $T_{\mathrm{C}}.$ $T_{\mathrm{C}}$ of the present compounds depend on the tolerance factor t and when t is larger than 0.913 the relations between $T_{\mathrm{C}}$ and t are almost the same as those observed in the perovskitelike compounds previously examined, which contain rare-earth metal ions, such as ${\mathrm{Y}}^{3+},\hspace{0.5em}{\mathrm{Pr}}^{3+},$ and ${\mathrm{Tb}}^{3+}.$ 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 ${\mathrm{Pr}}^{3+}$ and/or ${\mathrm{Y}}^{3+},$ but the same as that appears in the compound containing heavy rare-earth ions of ${\mathrm{Tb}}^{3+}.$ 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.