Magnetic Behavior of the 2-Leg and 3-Leg Spin Ladder CupratesSrn−1Cun+1O2n

Abstract

We have performed muon spin relaxation measurements of the spin-ladder cuprates ${\mathrm{Sr}}_{n-1\mathrm{}}{\mathrm{Cu}}_{n+1\mathrm{}}{\mathrm{O}}_{2n}$ ( $n=3,5\mathrm{}$). The 3-leg ladder system ( $n=5\mathrm{}$) shows static magnetic order at $T\sim 52\mathrm{K}$, which is between the ordering temperatures of the one-dimensional chain system ${\mathrm{Sr}}_2\mathrm{Cu}{\mathrm{O}}_3$ ( $T_N\sim 5\mathrm{K}$) and of the two-dimensional layer system ${\mathrm{Ca}}_{0.86}{\mathrm{Sr}}_{0.14}{\mathrm{CuO}}_2$ ( $T_N\sim 540\mathrm{K}$). The 2-leg ladder system ( $n=3\mathrm{}$) does not show any magnetic order down to 20 mK, in agreement with the theoretical prediction of a nonmagnetic ground state with a spin gap for even-leg-number ladder systems.