Paramagnetic susceptibility of disorderedN−methylphenazinium−tetracyanoquinodimethanide

The organic charge-transfer salt $N-\mathrm{methylphenazinium}-\mathrm{tetracyanoquinodimethanide}$ (NMP-TCNQ) is described in terms of the one-dimensional disordered Hubbard model. For low temperatures this model reduces, via a perturbation expansion, to that of a disordered Heisenberg antiferromagnet. The magnetic susceptibility of the latter can be adequately described by the disordered classical Heisenberg model. Fitting of susceptibility data by the one-dimensional classical Heisenberg model provides us with values $t=0.055\mathrm{}$ eV, $U_{\mathrm{eff}}=0.130\mathrm{}$ eV, and $\sigma =0.136\mathrm{}$ eV for the parameters of the original Hubbard Hamiltonian. The low-temperature heat capacity and strong-field magnetization are also analyzed.