STRUCTURAL, MAGNETIC, AND CRYSTALLINE ELECTRIC-FIELD EFFECTS IN SINGLE OF Y1-XPRXBA2CU3O7-DELTA

We report here structural and directional magnetic susceptibility meas urements on single crystals of Y1-xPrxBa2Cu3O7-delta (x = 1.0, delta = 1, 0.11; x = 0.7, delta = 0; and x = 0.42, delta = 0.22). The space g roup of PrBa2Cu3O6 (Pr-O6) and Y0.58Pr0.42Ba2Cu3O6.78 (Pr 0.42-O7) wer e found to be P4/mmm and that of PrBa2Cu3O6.89 (Pr-O7) was found to be Pmmm. Also, Pr-O7 was found to be weakly orthorhombic. Directional, m agnetic susceptibility measurements in the temperature range 2-300 K r evealed a clear peaking in the paramagnetic anisotropy of Pr-O7 around 17 K, and chi(c) > chi(a,b) at all temperatures. However for Y0.3Pr0. 7Ba2Cu3O7 (Pr0.7-O7) and Pr0.42-O7, chi(c) > chi(a,b) at room temperat ure and chi(c) < chi(a,b) for temperatures below 110 and 60 K, respect ively. The magnetic susceptibilities have been analyzed in the light o f crystalline electric-field effects considering J mixing of all the t hirteen multiplets. Intermediate coupled wave functions have also been used in the calculations. Crystal-field interaction is found to be st ronger in the case of Pr-O7 compared to Pr-O6 which is also evident fr om a shorter Pr-O bond length in the case of Pr-O7 than in Pr-O6. A be st set of eigenvalues and eigenfunctions has been determined and these are discussed and compared with inelastic neutron scattering data.