Multi-frequency ESR studies on (TMTTF)2X: evidence of the anisotropic Zeeman interaction in the charge ordered state


Multi-frequency ESR studies on (TMTTF)2X: evidence of the anisotropic Zeeman interaction in the charge ordered state

Yasin, S.; Salameh, B.; Dumm, M.; Dressel, M.

We studied the charge ordered (CO) state of the quasi 1-D S = 1/2 quantum spin chains (TMTTF)2X (X=SbF6 and AsF6) by comprehensive W-Band (95 GHz), Q-band (34 GHz) and X-Band (9.5 GHz) ESR experiments between 4 and 300 K in order to explore the nature of the exchange interaction in the CO state. At high temperatures, both compounds show a linear decrease of the linewidth with decreasing temperature; this behavior does not depend on the applied microwave frequency as well as the anisotropy of both, linewidth and g-value. Below TCO, the breaking of the inversion symmetry of the (TMTTF)2- dimers results in additional contributions DeltaHCO to the ESR linewidth. While the linewidth is frequency independent along the three principle magnetic axes a, b', and c*, it is substantially enhanced for the Q- and W-band measurements along the diagonal of a − b' plane. The enhanced linewidth along 45° in the a − b' plane below TCO shows a quadratic frequency dependence which is characteristic for anisotropic Zeeman interaction. From this finding we can conclude that the charge order leads to two inequivalent magnetic sites. We will compare this result to one obtained on anion-ordered TMTTF salts where a different charge-order pattern was proposed.

  • Poster
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2009, 22.-27.03.2009, Dresden, Deutschland

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Publ.-Id: 12646