Single crystal growth and study of the magnetic properties of the mixed spin-dimer system Ba$_{3-x}$Sr$_{x}$Cr$_{2}$O$_{8}$

TL;DR

This study investigates how substituting Sr with Ba in the spin-dimer system Ba$_{3-x}$Sr$_{x}$Cr$_{2}$O$_{8}$ affects its magnetic properties, using crystal growth, magnetization, and neutron scattering measurements.

Contribution

It provides the first detailed analysis of magnetic property changes due to chemical disorder in Ba$_{3-x}$Sr$_{x}$Cr$_{2}$O$_{8}$ through single crystal growth and neutron scattering.

Findings

Intradimer interaction constant reduced by 4% with Ba substitution.

Interdimer exchange interaction decreased by 6.9%.

Chemical disorder noticeably alters magnetic interactions.

Abstract

The compounds Sr$_{3}$Cr$_{2}$O$_{8}$ and Ba$_{3}$Cr$_{2}$O$_{8}$ are insulating dimerized antiferromagnets with Cr$^{5+}$ magnetic ions. These spin-$\frac{1}{2}$ ions form hexagonal bilayers with a strong intradimer antiferromagnetic interaction, that leads to a singlet ground state and gapped triplet states. We report on the effect on the magnetic properties of Sr$_{3}$Cr$_{2}$O$_{8}$ by introducing chemical disorder upon replacing Sr by Ba. Two single crystals of Ba$_{3-x}$Sr$_{x}$Cr$_{2}$O$_{8}$ with $x=2.9$ (3.33\% of $mixing$) and $x=2.8$ (6.66\%) were grown in a four-mirror type optical floating-zone furnace. The magnetic properties on these compounds were studied by magnetization measurements. Inelastic neutron scattering measurements on Ba$_{0.1}$Sr$_{2.9}$Cr$_{2}$O$_{8}$ were performed in order to determine the interaction constants and the spin gap for $x=2.9$. The intradimer interaction constant is found to be $J_0$=5.332(2) meV, about 4\% smaller than that of pure Sr$_{3}$Cr$_{2}$O$_{8}$, while the interdimer exchange interaction $J_e$ is smaller by 6.9\%. These results indicate a noticeable change in the magnetic properties by a random substitution effect.