Distribution of the magnetic environment in charge ordered La${}_{1.885}$Sr${}_{0.115}$CuO${}_4$

Abstract

We report the inverse Laplace transform (ILT) analysis of the ${}^{139}$La nuclear spin-lattice relaxation rate $1/T_1$ in charge ordered La${}_{1.885}$Sr${}_{0.115}$CuO${}_4$ ($T_{charge}\sim 80$K, $T_c\simeq T_{spin}^{neutron}=30$K), and shed new light on its magnetic inhomogeneity. We deduce the probability density function $P(1/T_1)$ of the distributed $1/T_1$ (i.e. the histogram of distributed $1/T_1$) by taking the inverse Laplace transform of the experimentally observed nuclear magnetization recovery curve $M(t)$. We demonstrate that spin freezing sets in in some domains precisely below the onset of charge order at $T_{charge}$, but their volume fraction grows only gradually toward $T_c$. Nearly a half of the sample volume exhibits properties expected for canonical high $T_c$ cuprates without charge order even near $T_c$. Our findings explain why charge order does not suppress $T_c$ of La${}_{1.885}$Sr${}_{0.115}$CuO${}_4$ as significantly as in La${}_{1.875}$Ba${}_{0.125}$CuO${}_4$.

Revised manuscript submitted to PRB