Nature of the Magnetic Order of Cu in Oxygen-DeficientNdBa2Cu3O6+x

Abstract

Neutron-diffraction measurements have been taken on single crystals of $\mathrm{Nd}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6+x}$ to explore the nature of the magnetic order as a function of oxygen concentration $x$. The Cu-O planes are known to order antiferromagnetically at $T_{\mathrm{N}1\mathrm{}}$, with $T_{\mathrm{N}1\mathrm{}}\left(x\approx 0\right)\simeq 450$ K. At lower temperatures we find that the oxygen-deficient Cu planes also order magnetically [$T_{\mathrm{N}2\mathrm{}}(x\approx 0.1)\simeq 80$ K], with a large ordered moment of $0.46{\mu }_{\mathrm{B}}$ and a simple antiferromagnetic sequencing along the $c$ axis. Both ordering temperatures decrease with increasing $x$, with $T_{\mathrm{N}2\mathrm{}}$ being much more sensitive to $x$ than $T_{\mathrm{N}1\mathrm{}}$.