Magnetic susceptibility studies on PrxY1-xBa2Cu3O7- delta single crystals in the insulating regime.

Abstract

We have performed magnetic-susceptibility measurements on single crystals of ${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ with 0.4\ensuremath{\le}x\ensuremath{\le}1, in the temperature range 5--300 K. The susceptibility at low temperature is nonlinear, however, above 100 K it is found to follow the Curie law. The values of the effective moment deduced is attributed to Pr in a 3+ valency state. This interpretation is consistent with the theoretical models that take into account the crystal-field effects on the trivalent Pr. The magnetic anisotropy studies indicate that the susceptibility along the c axis is greater than that along the ab plane in the entire temperature region 5--300 K. This observation favors the crystal-field schemes that have a ground state of ${\mathrm{\ensuremath{\Gamma}}}_{4}$ or ${\mathrm{\ensuremath{\Gamma}}}_{2}$ symmetry.