Finite-size effects in the quasi-one-dimensional quantum magnets Sr$_{2}$CuO$_{3}$, Sr$_{2}$Cu$_{0.99}$M$_{0.01}$O$_{3}$ (M = Ni, Zn), and SrCuO$_{2}$

Abstract: We studied the finite-size effects on the magnetic behavior of the quasi-one-dimensional spin S = $\frac{1}{2}$ Heisenberg antiferromagnets Sr${2}$CuO${3}$, Sr${2}$Cu${0.99}$M${0.01}$O${3}$ (M = Zn and Ni), and SrCuO${2}$. Magnetic susceptibility data were analyzed to estimate the concentration of chain-breaks due to extrinsically doped defects and/or due to slight oxygen off-stoichiometry. We show that the susceptibility of Sr${2}$Cu${0.99}$Ni${0.01}$O${3}$ can be described by considering Ni$^{2+}$ as a scalar defect ($S{eff}=0$) indicating that the Ni spin is screened. In Sr${2}$Cu${0.99}$Zn${0.01}$O${3}$ susceptibility analysis yields a defect concentration smaller than the nominal value which is in good qualitative agreement with crystal growth experiments. Influence of doping on the low-temperature long-range spin ordered state is studied. In the compound SrCuO$_{2}$, consisting of zigzag S = $\frac{1}{2}$ chains, the influence of spin frustration on the magnetic ordering and the defect concentration determined from the susceptibility data is discussed.