Heterometallic spin-1/2 quantum magnet under hydrostatic pressure

TL;DR

This study explores how hydrostatic pressure influences the magnetic properties and structure of a heterometallic Cu-V spin-1/2 dimer system, combining experimental and computational methods.

Contribution

It provides new insights into pressure-induced changes in magnetic interactions and confirms a unique exchange mechanism via combined ESR, susceptometry, and DFT analysis.

Findings

Pressure alters the spin-dimer phase diagram and magnetic interactions.

The exchange mechanism involves V(IV) ions contributing spin density to oxygen.

Dimer energy levels show non-linear field dependence due to dissimilar spins.

Abstract

We investigate the properties of CuVOF$_4$(H$_2$O)$_6$$\cdot$H$_2$O, in which two different spin species, Cu(II) and V(IV), form antiferromagnetic spin-1/2 dimers with weak interdimer coupling provided via hydrogen bonding. Using radio-frequency susceptometry and electron-spin resonance (ESR), we show how the temperature-magnetic field spin-dimer phase diagram evolves as a function of applied hydrostatic pressure and correlate this with pressure-induced changes to the crystal structure. These results, coupled with pressure-tuned DFT calculations, confirm the prior prediction that the primary exchange interaction is mediated via an unusual mechanism in which the V(IV) ions provide considerable spin density to the oxygen that joins the two spins in each dimer and which lies along the Jahn-Teller axis of the Cu(II) ion. In addition, the dissimilarity in the spins that make up each dimer unit leads to a non-linear field dependence of the electronic energy levels as detected in the ESR measurements.