Impurities in weakly coupled quantum spin chains Sr${}_2$CuO${}_3$ and SrCuO${}_2$

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 Sr${}_2$CuO${}_3$ using inelastic neutron scattering, specific heat and bulk magnetization measurements. We show that 1 \% Ni${}^{2+}$ doping in Sr${}_2$CuO${}_3$ results in a sizable spin gap in the spinon excitations, analogous to the case of Ni-doped SrCuO${}_2$ previously reported [ref. 1]. However, a similar level of Zn${}^{2+}$ doping in SrCuO${}_2$, 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.

Accepted in PRB

References in corpus (8)

• Spin-Orbital Separation in the quasi 1D Mott-insulator Sr2CuO3
• Evidence for Ballistic Thermal Conduction in the One-Dimensional S=1/2 Heisenberg Antiferromagnetic Spin System Sr2CuO3
• Disorder-induced Spin Gap in the Zigzag Spin-1/2 Chain Cuprate Sr_{0.9}Ca_{0.1}CuO_2
• 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${}_2$
• Spin Gap in the Single Spin-1/2 Chain Cuprate Sr${}_{1.9}$Ca${}_{0.1}$CuO${}_3$
• Crystal growth of the non-magnetic Zn${}^{2+}$ and magnetic Co${}^{2+}$ doped quasi one-dimensional spin chain compound SrCuO${}_2$ using the travelling solvent floating zone method
• Spin pseudogap in the $S=\frac{1}{2}$ chain material Sr${}_2$CuO${}_3$ with impurities
• Relaxation time spectrum of low-energy excitations in one- and two-dimensional materials with charge or spin density waves