Neutron Scattering and magnetization studies of Ba$_2$Cu$_{2.95}$Co$_{0.05}$O$_4$Cl$_2$: A decorated two-dimensional antiferromagnet

TL;DR

This study investigates how Co substitution affects the magnetic structure of Ba$_2$Cu$_3$O$_4$Cl$_2$, revealing preserved ordering, spin-glass behavior, and induced canted states through neutron scattering and magnetization analysis.

Contribution

It provides new insights into the magnetic interactions and states in Co-doped Ba$_2$Cu$_3$O$_4$Cl$_2$, highlighting the role of Co in modifying magnetic properties.

Findings

Co substitution preserves the magnetic ordering of Cu sublattices.

Spin-glass behavior occurs between the phase transitions.

Co moments induce local canted magnetic states.

Abstract

Ba$_2$Cu$_3$O$_4$Cl$_2$ has two inter-penetrating square Cu sublattices, one with square root 2 times the in-plane spacing of the other. Isotropic magnetic interactions between the two sublattices are completely frustrated. Quantum fluctuations resolve the intrinsic degeneracy in the ordering direction of the more weakly coupled sublattice in favor of collinear ordering. We present neutron scattering and magnetization studies of the magnetic structure when the Cu ions are substituted with Co. The Co spins create new magnetic interactions between the two sublattices. The ordering behavior of both Cu sublattices is retained largely unmodified. Between the phase transitions of the two sublattices spin-glass behavior is observed. Magnetization results show a strong enhancement to the ferromagnetic aspect of the magnetic structure. The combination of glassy behavior and large moments strongly suggest that the Co moments induce the formation of local canted states.