"Heat capacity of the site-diluted spin dimer system Ba3(Mn1xVx)2O8"

E. C. Samulon: M. C. Shapiro, and I. R. Fisher ; Phys. Rev. B, 08/05/11.

Additional Authors: M. C. Shapiro, and I. R. Fisher

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 ground state is a product of singlets. Substitution of nonmagnetic 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.