Magnetic properties of YB 2(Cu 0.94Zn 0.06) 3O x ( x = 6.0 to 7.0) studied by Mössbauer spectroscopy on substituted 170Yb 3+

Abstract

We have used 170Yb Mössbauer spectroscopy on Yb 3+ diluted at the Y 3+ sites to study YBa 2(Cu 0.94Zn 0.06) 3O x . In the fully oxygenated sample, the presence of Zn 2+ introduces a Korringa dependence of the Yb 3+ paramagnetic relaxation rate, indicating an increase in the density of states at the Fermi level, which is visible both above and below T c (32 K). A molecular field coming from the Cu (2) is observed on all the Yb 3+ probes in non-superconducting samples with x = 6.0 and 6.5 showing that at these oxygen levels, all the Cu (2)'s are locally magnetically correlated. For x = 6.88 molecular fields suggesting there is phase separation between local magnetic and non-magnetic superconducting regions. For x = 7.0, none of the Cu(2)'s are magnetically correlated. The general features of the oxygen-level dependence of the local magnetic properties are similar in the zinc-substituted and in the zinc-free samples, but magnetic ordering persists to higher oxygen levels when Zn 2+ is present.