Magnetic correlations in Pr 1− xY xBa 2Cu 3O 7 studied by Mössbauer spectroscopy on substituted 170Yb 3+

Abstract

We have used 170Yb 3+ Mössbauer spectroscopy on Yb 3+ diluted at the rare-earth sites in Pr - x Y x Ba 2Cu 3O 7 and in PrBa 2Cu 3O 6 to examine the magnetic properties associated with the (hybridized) Pr 3+ ions. Magnetic ordering in the non-superconducting compounds PrBa 2Cu 3O 7 ( T> = 16 K) and PrBa 2Cu 3O 7 ( T = 10 K) is identified by the appearance of a Pr 3+-derive d molecular field and by a change in the Yb 3+ paramagnetic relaxation rates. Evidence is presented suggesting the ordered Pr 3+ magentic moments are aligned well away from the c-axis. The splitting of the three lowest crystal-field levels in PrBa 2Cu 3O 6 is estimated to be about half that (∼ 50 K) in PrBa 2Cu 3O 7. In the superconducting samples of Pr 1- x Y x Ba 2Cu 3O 7, the Yb 3+ l ocal probes give evidence for an inhomogeneous behavior linked to statistical variations in the Pr 3+/Y 3+ occupancies. With increasing x, both the volume of the sample showing local Pr 3+ magnetic order and the average ordering temperature decreases. There appears to be an anti-correlation between the superconducting transition temperature and the volume of the sample showing Pr 3+ magnetic order, suggesting the local Pr 3+ concentration needed to remove superconductivity (in favor of Cu (2)-based magnetic order) is near that needed to support local Pr 3+ magnetic order.