Strong correlation between field-induced magnetism and superconductivity in Pr0.89LaCe0.11CUO4

We report the local magnetic response of an electron-doped cuprate superconductor, Pr0.89LaCe0.11CuO4-y (T-c similar or equal to 26 K), studied by muon spin rotation (muSR) over a field range from 200 Oe to 50 kOe. In the paramagnetic state, the muon Knight shift along the crystal c-axis (K) is proportional to the in-plane susceptibility chi(ab). More surprisingly, K-mu(z) is strongly enhanced by the occurrence of superconductivity (below similar to40 kOe), changing its sign from positive to negative around -1 kOe with increasing field. This finding can be understood by considering the weak polarization of Pr ions due to the superexchange interaction with the antiferromagnetic Cu sublattice, which coexists with superconductivity.