Finite-size effects in the quasi-one-dimensional quantum magnets Sr2CuO3,Sr2Cu0.99M0.01O3(M=Ni,Zn), and SrCuO2

Abstract

We studied the finite-size effects on the magnetic behavior of the quasi-one-dimensional spin S = 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 = 1 2 chains, the influence of spin frustration on the magnetic ordering and the defect concentration determined from the susceptibility data is discussed.