Magnetic properties of Pr2–xFe1 + xSbO7 and Bi2–xLnxFeSbO7 (Ln = La, Pr) pyrochlore solid solutions

Resumo

The Bi–La–Fe–Sb–O, Pr–Fe–Sb–O, and Bi–Pr–Fe–Sb–O systems have been shown to contain pyrochlore solid solutions. We have determined the limits of the Pr_2–xFe_{1 + x}SbO₇ and Bi_2–xLn_xFeSbO₇ (Ln = La, Pr) solid solutions and shown that there is no compound corresponding to the “ideal” composition Pr₂FeSbO₇. Analysis of the magnetic properties of the synthesized compounds indicates that rare earth substitution for bismuth ions has no effect on the spin glass transition and that the spin glass state is only determined by the interaction between the Fe³⁺ spins on the octahedral site. The Pr³⁺ paramagnetic ion in Pr_2–xFe_{1 + x}SbO₇ does not participate in the formation of the spin glass state but makes a paramagnetic contribution to the total magnetic susceptibility, which is especially significant at low temperatures.