Triplet Dimerization Crossover Driven by Magnetic Frustration in In2VO5

TL;DR

This study reveals a magnetic crossover in In2VO5 where spins form triplet dimers below 120 K, with a further transition to a singlet state at 2.5 K, driven by magnetic frustration and spin-lattice coupling.

Contribution

It uncovers a novel magnetic dimerization crossover driven by frustration without structural dimerization, highlighting spin-lattice interactions in In2VO5.

Findings

Triplet dimers form below 120 K

No long-range magnetic order down to 0.42 K

Lattice anomalies indicate spin-lattice coupling

Abstract

In2VO5, containing magnetically frustrated zig-zag chains, shows a remarkable magnetic crossover at 120 K between paramagnetic states with positive (17 K) and negative (-70 K) Weiss temperatures. Magnetic moment and entropy data show that the V4+ S = 1/2 spins condense into S = 1 triplet dimers below the crossover. A further freezing of the antiferromagnetically coupled triplet dimers into a global singlet state is observed at 2.5 K, with no long range magnetic order down to 0.42 K and in fields up to 9 T. No structural V-V dimerization is observed by high-resolution X-ray diffraction down to 10 K, but a subtle lattice anomaly evidences a spin-lattice coupling in the triplet dimer state. This is assigned to longitudinal oxygen displacement modes that reduce frustration within the chains and so couple to the spin dimer fluctuations.