We present a multifrequency electron spin resonance study in the range of 4-420 GHz of the quasi-one-dimensional, nondimerized, quarter-filled Mott insulators, δ- ( EDT-TTF-CONMe2 ) 2 X (X= AsF 6 ,Br ). In the high-temperature orthorhombic phase above T∼190 K, the magnitude and the temperature dependence of the high-temperature spin susceptibility are described by a S= 1 2 Heisenberg antiferromagnetic chain with J AsF6 =298 K and JBr =474 K coupling constants for X= AsF6 and Br, respectively. We estimate from the temperature dependence of the linewidth (ΔH) an exchange anisotropy, J′ /J of ∼2× 10-3. The frequency dependence of ΔH and the g shift have an unusual quadratic dependence in all crystallographic orientations that we attribute to an antisymmetric exchange (Dzyaloshinskii-Moriya) interaction.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jun 29 2010|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics