MAGNETIC SUSCEPTIBILITIES OF TCNQ COMPLEXES

The magnetic susceptibility (χ) of several highly conductive TCNQ complexes was measured in the temperature range from 2.5°K to room temperature. χ is composed of diamagnetic part (χd), a paramagnetic part (χc) caused by crystal imperfections, and an intrinsic paramagnetic part (χp). Three parts can be separated unambiguously, provided that χc obeys Curie's law and χp approaches zero as temperature is lowered. χp of Et3NH(TCNQ)2 below 300°K and that of DAD(TCNQ)2 below 30°K are well explained by one triplet state per four TCNQ molecules at 310 cm-1 and 120 cm-1 above the ground singlet, respectively. Temperature dependence of χp of DAD(TCNQ)2 from 30°K to 300°K cannot be explained quantitatively, though χp tends to coincide with that of undegenerated electron gas at high temperatures. For Q(TCNQ)2, BiP(TBNQ)2 and NMePh(TCNQ), χ were unsuccessfully separated, since χc deviated from the Curie's law owing to the high concentration of impurities in the samples. These results are discussed with the results of far infrared absorption spectra of these materials at 300°K and 1.5°K. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.