Magnetic structure and spin dynamics of the quasi-2D antiferromagnet Zn-doped copper pyrovanadate

TL;DR

This study investigates the magnetic structure and spin dynamics of Zn-doped copper pyrovanadate, revealing a 2D anisotropic spin network with specific exchange interactions and confirming its similarity to related compounds.

Contribution

It provides detailed experimental insights into the magnetic properties and spin interactions of ZnCVO, challenging previous theoretical predictions about its spin network structure.

Findings

ZnCVO has a 2D anisotropic spin network with specific exchange interactions.

Spin waves show strong in-plane and weak interplane interactions.

The spin network differs from the predicted honeycomb structure.

Abstract

Magnetic properties of the antiferromagnet Zn$_{0.15}$Cu$_{1.85}$V$_2$O$_7$ (ZnCVO) have been thoroughly investigated on powder and single-crystal samples. The crystal structure determination using powder x-ray and neutron diffraction confirms that ZnCVO with Zn = 0.15 is isostructural with $\beta$-Cu$_{2}$V$_2$O$_7$ ($\beta$-CVO) with small deviation in the lattice parameters. Macroscopic magnetic properties measurements also confirm the similarity between the two compounds. The Cu$^{2+}$ spins were found to align along the crystallographic $c$-axis, antiparallel to their nearest neighbors connected by the leading exchange interaction $J_1$. Spin dynamics reveals a typical symmetric spin-wave dispersion with strong interactions in the $bc$-plane and weak interplane coupling. The exchange interaction analysis indicates that the spin network of ZnCVO is topologically consistent with the previous DFT prediction but the values of leading exchange interactions are contradictory. Furthermore, rather than the predicted 2D honeycomb structure, the spin network in ZnCVO could be better described by the anisotropic 2D spin network composing of $J_1$, $J_5$, and $J_6$ interactions, four bonds per one spin site, coupled by weak interplane interactions.