Quasi-one-dimensional magnetic properties of NiNb2−xVxO6 compounds synthesized at high pressure in a nonstandard columbite-type structure

Abstract

We report on the low-dimensional magnetic behavior of the series of compounds ${\mathrm{NiNb}}_{2\ensuremath{-}x}{\mathrm{V}}_{x}{\mathrm{O}}_{6}$ ($0\ensuremath{\le}x\ensuremath{\le}2$), with a columbite-type crystal structure stabilized at high pressure and temperature. Based on susceptibility, magnetization, and specific-heat measurements, the system is characterized as presenting quasi-one-dimensional magnetism, with ${\mathrm{Ni}}^{2+}$ magnetic moments that can be modeled as Ising spins, placed along zigzag chains in the crystal structure. The low-temperature phase is found to consist of an antiferromagnetic arrangement of ferromagnetic chains, and a metamagnetic transition to uniform ferromagnetic order is observed under magnetic fields slightly above ${\ensuremath{\mu}}_{0}H=1\phantom{\rule{4pt}{0ex}}\mathrm{T}$. We discuss the effects of substituting vanadium for niobium, maintaining the same crystal structure along the whole series of samples. In particular, the long-range magnetic order, most clearly seen for $x=0$, tends to be suppressed as the vanadium content is increased. The exchange interactions are quantified, revealing that the ferromagnetic intrachain interactions vary from about $7\phantom{\rule{4pt}{0ex}}\mathrm{K}$ for ${\mathrm{NiNb}}_{2}{\mathrm{O}}_{6}$ to $2\phantom{\rule{4pt}{0ex}}\mathrm{K}$ for ${\mathrm{NiV}}_{2}{\mathrm{O}}_{6}$, remaining one order of magnitude larger than the mean antiferromagnetic interchain coupling.