“…Nuclear spin-lattice relaxation in a randomly diluted magnetic system has long been studied [13,14], and the nuclear spin-lattice relaxation in type-II superconductor was recently analyzed by treating vortices as paramagnetic impurities [15,16]. In a randomly diluted magnetic system, the magnetic ion concentration, which determines the percolation of exchange interaction path, is an important factor in the nuclear spin-lattice relaxation.…”