Magnetic inhomogeneity in charge-ordered La1.885Sr0.115CuO4 studied by NMR

We report the inverse Laplace transform analysis of the La139 nuclear spin-lattice relaxation rate 1/T1 (ILTT1 analysis) in charge-ordered La1.885Sr0.115CuO4 (Tcharge≃80 K, Tc≃Tspinneutron=30 K), and shed light on its magnetic inhomogeneity. We deduce the probability density function P(1/T1) of the distributed 1/T1 (i.e., the histogram of distributed 1/T1) 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 Tcharge, but their volume fraction grows only gradually toward Tc. Nearly a half of the sample volume exhibits properties expected for canonical high-Tc cuprates without charge order even near Tc. Our findings explain why charge order does not suppress Tc of La1.885Sr0.115CuO4 as significantly as in La1.875Ba0.125CuO4.