Magnetic properties of poly(metal phosphinates): The effects of structural disorder on one-dimensional antiferromagnetic chains

The magnetic properties of several materials from the class poly(metal phosphinates) have been measured. In particular ESR spectra and the temperature dependence of the static susceptibility of three poly (chromium phosphinates) imply that these polymers comprise a class of one-dimensional antiferromagnetic chains with $\frac{J}{k}\sim 4$ K and with a varying degree of crystallinity. Structural disorder is found to limit the range of spin correlations and, in the extreme case, prohibits extended short-range order. The data are analyzed in terms of a model of chains of constant exchange but finite length. Comparison is made with an alternative model of infinite chains with Heisenberg exchange $J$ varying randomly about a mean. The width of the distribution of $J$ provides a direct measure of the disorder in each system.