Strong correlation between field-induced magnetism and superconductivity in Pr${}_{0.89}$LaCe${}_{0.11}$CuO${}_4$

Abstract

We report the local magnetic response of an electron-doped cuprate superconductor, Pr${}_{0.89}$LaCe${}_{0.11}$CuO${}_4$ ($T_c\simeq 26$ K), studied by muon spin rotation (\msr) over a field range from 200 Oe to 50 kOe. In the paramagnetic state, the muon Knight shift along the crystal c-axis ($K_{\mu }^z$) is proportional to the in-plane susceptibility ${\chi }_{ab}$. More surprisingly, $K_{\mu }^z$ is strongly enhanced by the occurrence of superconductivity (below $\sim$40 kOe), changing its sign from positive to negative around $\sim 1$ kOe with increasing field. This finding can be understood by considering the weak polarization of Pr ions due to superexchange interaction with the antiferromagnetic Cu sublattice, which coexists with superconductivity.

4 pages, 4figures, submitted to J. Phys. Soc. Jpn