Structural and magnetic properties in the quantum S=1/2 dimer systems Ba3(Cr1-xVx)2O8 with site disorder

TL;DR

This study investigates how site disorder via vanadium substitution affects the structural and magnetic properties of Ba3(Cr1-xVx)2O8, revealing a stable singlet ground state with reduced dispersion bandwidth as disorder increases.

Contribution

It provides a comprehensive experimental analysis of the effects of vanadium-induced site disorder on the quantum S=1/2 dimer system Ba3(Cr1-xVx)2O8, including structural transitions and magnetic excitations.

Findings

Jahn-Teller transition temperature decreases with vanadium substitution.

The singlet ground state remains unchanged across different x values.

Spin gap energy remains constant at 1.3 meV despite disorder.

Abstract

We report a comprehensive study of dc susceptibility, specific heat, neutron diffraction, and inelastic neutron scattering measurements on polycrystalline Ba3(Cr1-xVx)2O8 samples, where x=0, 0.06, 0.15, and 0.53. A Jahn-Teller structure transition occurs for x=0, 0.06, and 0.15 samples and the transition temperature is reduced upon vanadium substitution from 70(2) K at x=0 to 60(2) K at x=0.06 and 0.15. The structure becomes less distorted as x increases and such transition disappears at x=0.53. The observed magnetic excitation spectrum indicates that the singlet ground state remains unaltered and spin gap energy \Delta=1.3(1) meV is identical within the instrument resolution for all x. In addition, the dispersion bandwidth W decreases with increase of x. At x=0.53, W is reduced to 1.4(1) meV from 2.0(1) meV at x=0.