Quantum Optics Laboratory

We conducted a detailed study of the structure and magnetic properties of (R1-xPrx)Ba2Cu3O7 sintered samples, where R = Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, Sm, and Nd for x = 0.5-1.0. We found that the temperature dependence of the dc susceptibility follows the Curie-Weiss law in the temperature range 20-300 K and the paramagnetism of the Pr and R sublattices exist independently of one another. The antiferromagnetic ordering temperature T(N) of Pr ions decreases monotonically with increasing R concentration (1-x). At a given x, T(N) is R-ion-size dependent. The slope in the T(N) vs x curve is steeper for ions with smaller ionic radii. The observed results are interpreted in terms of the hybridization between the local states of the Pr ion and the valence-band states of the CuO2 planes.

The magnetic ordering temperatures T(m) of Pr ions in (R1-xPrx)Ba2Cu3O7 systems (R = Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm, Nd and Y) with x = 0.5 - 1.0 were measured. We observe that T(m) decreases monotonically with increasing R concentration. At constant x, T(m) is R ion-size dependent. The slope in the T(m) vs. x is steeper for ion with smaller ionic radius. In comparison with the ion-size effect on the superconducting transition temperatures T(c) in these systems, the observed results can be qualitatively interpreted in terms of the hybridization between the local states of Pr ion and the conduction band states of the CuO2 planes.