Motivated by the experimental report of unusual low-temperature magnetism in the quasi-one-dimensional magnet ${\mathrm{CuInVO}}_5$, we present results of a cluster mean-field study on a spin-$1/2$ Heisenberg model with alternating ferromagnetic and antiferromagnetic nearest-neighbor coupling. We map out the ground-state phase diagrams with varying model parameters, including the effect of an external magnetic field. An unexpected competition between different spin-spin correlations is uncovered. Multiple spin-flop transitions are identified with the help of component-resolved correlation functions. For the material-specific choice of model parameters we discuss the temperature dependence of specific heat and magnetic susceptibility and compare our results with the available experimental data. A detailed account of spin-spin correlations allows us to present a microscopic understanding of the low-temperature magnetic ordering in ${\mathrm{CuInVO}}_5$. Most notably, we identify the origin of an extra peak in the low-temperature specific heat data of ${\mathrm{CuInVO}}_5$ reported by Hase et al. [Phys. Rev. B 94, 174421 (2016)].

• Received 3 May 2018
• Revised 5 August 2018

DOI:https://doi.org/10.1103/PhysRevB.98.104429