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Heterometallic spin-1/2 quantum magnet under hydrostatic pressure

M. J. Coak, D. Kamenskyi, S. P. M. Curley, B. M. Huddart, J. P. Tidey, A. Chmeruk, T. Sakurai, S. Okubo, H. Ohta, S. Kimura, H. Nojiri, D. Graf, S. J. Clark, Z. E. Manson, J. L. Manson, T. Lancaster, P. A. Goddard

TL;DR

The study addresses how hydrostatic pressure tunes exchange interactions in a heterometallic spin-$\frac{1}{2}$ dimer Cu(II)/V(IV), a system with explicit rotational-symmetry breaking due to dissimilar ions. It combines high-field ESR, RF susceptometry, pressure-dependent X-ray diffraction, and DFT to connect magnetic behavior with structural evolution under pressure. It identifies the dominant intradimer exchange as Cu–O–V mediated along Cu's Jahn–Teller axis, showing $J_0$ increases with pressure up to a structural phase transition while interdimer coupling remains small. The results demonstrate how pressure can control symmetry-breaking magnetic interactions in heterometallic spin-$\frac{1}{2}$ dimers, with implications for quantum magnetism and pressure-tuned triplon phenomena.

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.

Heterometallic spin-1/2 quantum magnet under hydrostatic pressure

TL;DR

The study addresses how hydrostatic pressure tunes exchange interactions in a heterometallic spin- dimer Cu(II)/V(IV), a system with explicit rotational-symmetry breaking due to dissimilar ions. It combines high-field ESR, RF susceptometry, pressure-dependent X-ray diffraction, and DFT to connect magnetic behavior with structural evolution under pressure. It identifies the dominant intradimer exchange as Cu–O–V mediated along Cu's Jahn–Teller axis, showing increases with pressure up to a structural phase transition while interdimer coupling remains small. The results demonstrate how pressure can control symmetry-breaking magnetic interactions in heterometallic spin- dimers, with implications for quantum magnetism and pressure-tuned triplon phenomena.

Abstract

We investigate the properties of CuVOF(HO)HO, 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.

Paper Structure

This paper contains 3 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Methods
  3. Results

Figures (1)

  • Figure 1: Local structure of Cu(II)–V(IV) dimer units of CuVOF$_4$(H$_2$O)$_6 \cdot$H$_2$O measured at 150 K using X-ray diffraction. Red striped bonds indicate the Jahn-Teller axis of the Cu(II) ion, while blue stripes highlight the intradimer hydrogen bonds. The intradimer exchange $J_0$ is predicted to be mediated through the central oxygen atom via an atypical exchange mechanism Curley2021a.