Specific heat of disordered antiferromagnetic chains: Poly(metal phosphinates)

Abstract

The inorganic transition-metal polymers, poly(metal phosphinates), comprise a unique and versatile class of new materials. In particular, three poly(chromium phosphinates) have been shown to form linear polymeric molecules, which may be described in terms of spin chains with antiferromagnetic interactions. The specific heats of these materials and of their nonmagnetic analogs, poly(zinc phosphinates), have been measured in the temperature range $1.6\ensuremath{\lesssim}T\ensuremath{\lesssim}10$ K. The vibrational contribution to the specific heat is consistent with the polymeric nature of the materials, changing from ${T}^{3}$ to ${T}^{\frac{5}{2}}$ dependence as the temperature increases. The magnetic specific heat can then be extracted and is found to be in qualitative agreement with a model which includes disorder in the spin chains. We believe that this is the first measurement of the specific heat of a disordered one-dimensional magnetic system.