Heat capacity of the site-diluted spin dimer system Ba3(Mn1-xVx)2O8

TL;DR

This study investigates how non-magnetic V ions affect the low-temperature magnetic properties of Ba3(Mn1-xVx)2O8, revealing a transition to a random singlet phase without phase transition signatures.

Contribution

It provides the first detailed heat capacity and susceptibility analysis of dilute Ba3(Mn1-xVx)2O8, identifying a low-temperature random singlet phase due to site dilution.

Findings

Progressive removal of magnetic entropy with no phase transition

Concentration dependence inconsistent with spin glass behavior

Evidence for a low-temperature random singlet phase

Abstract

Heat capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba3(Mn1-xVx)2O8. The parent compound Ba3Mn2O8 is a spin dimer system based on pairs of antiferromagnetically coupled S = 1, 3d2 Mn5+ ions such that the zero field groundstate is a product of singlets. Substitution of non-magnetic S = 0, 3d0 V5+ ions leads to an interacting network of unpaired Mn moments, the low temperature properties of which are explored in the limit of small concentrations, 0<x<0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for a phase transition. The concentration dependence does not conform to expectations for a spin glass state. Rather, the data suggest a low temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.