Impurities in the weakly coupled quantum spin chains Sr2CuO3 and SrCuO2

Abstract

We study the effect of non-magnetic Zn 2+ (spin-0) and magnetic Ni 2+ (spin-1) impurities on the ground state and low-lying excitations of the quasi-one-dimensional spin-1/2 Heisenberg antiferromagnet Sr2CuO3 using inelastic neutron scattering, specific heat and bulk magnetization measurements. We show that 1 % Ni 2+ doping in Sr2CuO3 results in a sizable spin gap in the spinon excitations, analogous to the case of Ni doped SrCuO2 previously reported [ref. 1]. However, a similar level of Zn 2+ doping in SrCuO2, investigated here for comparison, did not reveal any signs of a spin gap. Magnetic ordering temperature was found to be suppressed in the presence of both Zn 2+ and Ni 2+ impurities, however, the rate of suppression due to Ni 2+ was found to be much more pronounced than for Zn 2+ . Effect of magnetic field on the ordering temperature is investigated. We found that with increasing magnetic field, not only the magnetic ordering temperature gradually increases but the size of specific heat anomaly associated with the magnetic ordering also progressively enhances, which can be qualitatively understood as due to the field induced suppression of quantum fluctuations.

Unexpected magnetic phase in the weakly ordered spin- 12 chain cuprate Sr2CuO3

“…3. Our data match well the results of specific heat measurements [17] performed in a narrower field range. Being in qualitative agreement with previous results for other quasi-one-dimensional Heisenberg antiferromagnets (see, e.g., Refs.…”

Multi-spinon and antiholon excitations probed by resonant inelastic x-ray scattering on doped one-dimensional antiferromagnets

“…Our work provides strong motivation for RIXS experiments at the oxgen K-edge of doped 1D AFMs. The recent RIXS experiment at the O K-edge of undoped Sr 2 CuO 3 [15] and the availability of doped Sr 2 CuO 3 and SrCuO 2 crystals [18,19,44] demonstrate that our predictions can be verified experimentally in the near future.…”

“…Specifically, we show that O K-edge RIXS can access multi-spinon excitations, antiholon excitations, and combinations thereof, thus providing a unique view of spin-charge separation in doped 1D AFMs. Since Sr 2 CuO 3 can be doped with Zn, Ni, or Co [18,19] The dynamics in the intermediate state are essential for generating magnetic excitations at this edge, and this is a fundamental difference in how RIXS and INS probe magnetic excitations. One of the advantages of working at the O K-edge is that it has relatively long core-hole lifetimes ( n  G , Γ n =0.15 eV [23]) in comparison to other edges (Γ n =1.5 eV at the Cu K-edge and 0.3 eV at the Cu L 3 -edge [24]), which provides a longer window for generating magnetic excitations [15,25].…”

Particle-hole asymmetry in the dynamical spin and charge responses of corner-shared 1D cuprates

“…These models generally provide an excellent description of the magnetic excitations -in this case a multi-spinon continuum -observed in INS [40][41][42][43] and RIXS 44,45 experiments. The spin and charge excitations of doped samples have received comparatively less attention because doping electrons or holes in Sr 2 CuO 3 has proved to be challenging [49][50][51] . However, the Ba 2−x Sr x CuO 3+δ system offers new possibilities in this regard 36 .…”