Frustration induced one-dimensionality in the isosceles triangular   antiferromagnetic lattice of $\delta$-(EDT-TTF-CONMe$_{2}$)$_{2}$AsF$_6$
  The $1/4$-filled organic compound, $\delta$-(EDT-TTF-CONMe$_{2}$)$_{2}$AsF$_6$ is a frustrated two-dimensional triangular magnetic system as shown by high-frequency (111.2 and 222.4 GHz) electron spin resonance (ESR) and structural data in the literature. The material gradually orders antiferromagnetically below 40~K but some magnetically disordered domains persist down to 4 K. We propose that in defect free regions frustration prevents true magnetic order down to at least 4 K in spite of the large first- and second-neighbor exchange interactions along chains and between chains, respectively. The antiferromagnetic (AFM) order gradually developing below 40 K nucleates around structural defects that locally cancel frustration. Two antiferromagnetic resonance modes mapped in the principal planes at 4~K are assigned to the very weakly interacting one-dimensional molecular chains in antiferromagnetic regions. 
B. N\'afr\'adi and A. Antal and T. Feh\'er and L.F. Kiss and C.   M\'ezi\`ere and P. Batail and L. Forr\'o and A. J\'anossy
cond-mat.str-el