Ferromagnetic versus molecular ordering in C60 charge transfer complexes

Magnetic ordering in fullerene charge-transfer complexes

“…Experimental observation has reported that TMBI-C 60 has a weakly PARA ground state with the electronic structure of TMBI 2ϩ -C 60 2Ϫ . 15 This can be due to the stronger electron-donating ability of TMBI than that of TDAE, that is, E 1 vs SCE is Ϫ0.83 V and Ϫ0.63 V for these donors, respectively, 15 which could relate to the energy level difference in TMBI-C 60 (⑀ϭϪ0.73 eV͒ being smaller than that in TDAE-C 60 (⑀ϭ0.05 eV͒. Hence TMBI-C 60 is regarded as the deeply doped system ͑b͒ in the present model.…”

“…We can further conclude that this DIA phase is contaminated by the PARA ingredient being consistent with the experiment. 15 Hence, the charge transfer in the ground state of the deeply doped system should be D ϩ2ϩ␦ -A Ϫ2 -D ϩ2Ϫ␦ -A Ϫ2 (0Ͻ␦Ͻ1).…”

“…Ϫ and TDAE ϩ spins are strongly coupled from the result of a Q-band ESR measurement, 14,15 and, thus, a TDAE radical cation should also play an important role in the magnetism of the TDAE-C 60 solid. Raman spectroscopy of TDAE-C 60 and TDAE-C 70 has also shown the presence of a TDAE monocation.…”

“…1͑b͔͒ does not show FM but diamagnetic ͑DIA͒ or weakly paramagnetic ͑PARA͒ behavior. 15 In TMBI-C 60 two electrons seem to be transferred into C 60 resulting in TMBI 2ϩ -C 60 2Ϫ . 15 This is because TMBI is a stronger donor than TDAE or, in other words, TMBI-C 60 is a more deeply doped system than TDAE-C 60 .…”

The universality of the electron spin relaxation in C60 mono radical anion salts: EPR studies of the model system [P(C6H5)4]2C60X

“…Long range anti ferromagnetic order, is in our opinion prevented as a consequence of the JT distortion. A proper arrangement of the C 60 anions relative to each other, providing minimal electrostatic repulsion occurs if the poles of the JT distorted C 60 anions are placed in the contact region [18]. Here the spin density and thus also the exchange is very small, and other mechanisms like spin polarization or configuration interaction control the magnetic properties [19].…”