${}^{139}$La-NMR study of spin-dynamics coupled with hole mobility in $T$*-type La${}_{0.86}$Eu${}_{0.86}$Sr${}_{0.28}$CuO${}_{4-\delta }$

Abstract

In $T$*-type cuprate oxides with five oxygen coordination, little is known about the relationship between the spin correlations and dope carriers. We performed ${}^{139}$La-nuclear magnetic resonance (NMR) and electrical resistivity measurements on an as-sintered (AS) and oxidation annealed (OA) polycrystalline $T$*-type La${}_{0.86}$Eu${}_{0.86}$S${}_{0.28}$CuO${}_4$ (LESCO) to investigate its magnetic and superconducting (SC) properties. Upon cooling, the NMR spectrum of AS LESCO broadened below 3 K, at which the nuclear spin-lattice relaxation rate $1/T_1$ against the temperature exhibited a maximum, thereby indicating the appearance of static magnetism. The temperature dependence of $1/T_1$ between 3 K and 20 K was similar to that of the resistivity displaying the semiconducting behavior. Furthermore, the energy scale of the transport gap and spin-dynamics estimated was found to be comparable. These results suggest a close connection between the mobility of the doped carriers and low-energy spin-dynamics, as reported for lightly doped $T$-type La${}_{2-x}$Sr${}_x$CuO${}_4$. In the OA SC sample, we confirmed the absence of a magnetic order and the Korringa relation above 10 K. Therefore, in the $T$*-type LESCO with $x$ = 0.28, the magnetic state coupled with holes drastically turns to the weakly correlated metallic state by oxidation annealing.

6 pages, 6 figures