Magnetic ordering in the ultra-pure site-diluted spin chain materials SrCu$_{1-x}$Ni$_x$O$_2$

TL;DR

This study uses muon spin rotation to investigate how tiny amounts of Ni impurities affect magnetic order in ultra-pure SrCuO2, revealing that even 0.5% Ni suppresses magnetic ordering.

Contribution

It demonstrates that minimal Ni doping causes inhomogeneous magnetic order and suppresses transition temperature, challenging previous assumptions of homogeneity in the parent compound.

Findings

Homogeneous magnetic order in pure SrCuO2

Ni impurities induce inhomogeneity in magnetic order

Magnetic order is suppressed at 0.5% Ni concentration

Abstract

Muon spin rotation technique is used to study magnetic ordering in ultra-pure samples of SrCu$_{1-x}$Ni$_x$O$_2$, an archetypical $S=1/2$ antiferromagnetic Heisenberg chain system with a small amount of $S=1$ defects. The ordered state in the parent compound is shown to be highly homogeneous, contrary to previous report [M. Matsuda et al., Phys. Rev. B \textbf{55}, R11953 (1997)]. Even minute amount of Ni impurities result in inhomogeneous order and a decrease of the transition temperature. At as little as $0.5$~\% Ni concentration, magnetic ordering is entirely suppressed. The results are compared to previous theoretical studies of weakly coupled spin chains with site-defects.