Magnetic susceptibility of $\alpha$ and $\beta$ phases of di[bis(ethylenediothiolo)tetrathiafulvalene] tri-iodide [${\mathrm{}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}-\mathrm{T}\mathrm{T}\mathrm{F})\mathrm{}}_2$${\mathrm{I}}_3$] under pressure

We report static magnetic susceptibility data, $\chi \mathrm{}\left(T\right)\mathrm{}$, for the $\alpha$ and $\beta$ phases of the organic conductor di[bis(ethylenediothiolo)tetrathiafulvalene] tri-iodide [${\mathrm{}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}-\mathrm{T}\mathrm{T}\mathrm{F})\mathrm{}}_2$ ${\mathrm{I}}_3$] both at ambient pressure and under applied pressures of up to 10 kbar. Ambient pressure ESR data for both phases below 300 K are also presented. The temperature dependence of the spin susceptibility ${\chi }_s^{\beta }\mathrm{}\left(T\right)\mathrm{}$ for the superconductor $\beta$-${\mathrm{}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}-\mathrm{T}\mathrm{T}\mathrm{F})\mathrm{}}_2$ ${\mathrm{I}}_3$ is unusually small for organic conductors; the pressure derivative $\partial \ln \frac{{\chi }_s^{\beta }}{\partial P}$ is found to be only moderate in magnitude (-3.3% per kbar) and independent of temperature below 300 K. For the $\alpha$q phase, $\partial \ln \frac{{\chi }_s^{\alpha }}{\partial P}\simeq -\frac{2.0\%}{\mathrm{Kbar}}$ at ambient temperature.