Magnetic structure ofCu2CdB2O6exhibiting a quantum-mechanical magnetization plateau and classical antiferromagnetic long-range order

Abstract

In ${\text{Cu}}_{2}{\text{CdB}}_{2}{\text{O}}_{6}$, a quantum-mechanical 1/2 magnetization plateau and classical antiferromagnetic long-range order (AF-LRO) appear. Two crystallographic Cu sites (Cu1 and Cu2) exist and have spin-1/2. It was speculated previously that spins on the Cu1 sites were in a nearly singlet state and that spins on the Cu2 sites formed the long-range order in weak magnetic fields and were almost saturated in fields of the magnetization plateau. As described herein, we report the magnetic structure of ${\text{Cu}}_{2}{^{114}\text{C}\text{d}}^{11}{\text{B}}_{2}{\text{O}}_{6}$ as determined using neutron powder-diffraction measurements. Contrary to that previous speculation, both the Cu1 and Cu2 spins have large magnetic moments in the ordered state. We discuss the mechanism which causes the magnetization plateau and AF-LRO.