Low-temperature heat capacity of acridinium ditetracyanoquinodimethanide [acridinium(TCNQ)2]

The heat capacity of a high-purity sample of acridinium dietetracyanoquinodimethanide [acridinium ${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}_2$ or Ad${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}_2$] was measured at temperatures from 0.5-10 K in fields of 0, 10, 20, and 40 kOe. The results are shown to correspond very well, within the experimental accuracy, to a superposition of a $T^3$ lattice contribution and a random-exchange antiferromagnetic Heisenberg-chain magnetic contribution. The Bulaevskiĭ theory parameters derived from these heat-capacity measurements without the use of any exogenous data are found to be $\alpha =0.75\mathrm{}\pm 0.01$ and $A=(1.69\mathrm{}\pm 0.04)\times {10}^{-3\mathrm{}}$ ${\mathrm{K}}^{-0.25\mathrm{}}$. The Debye temperature is found to be 68.3±0.2 K.