X-ray irradiation effect on magnetic properties of Dimer-Mott insulators: kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl and beta '-(BEDT-TTF)(2)ICl2

We report the X-ray irradiation dose dependence of the magnetic susceptibility in kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl (kappa-Cl) and beta'-(BEDT-TTF)(2)ICl2 (beta'-ICl2)The Neel temperature of 27 5 K in kappa-Cl reduces to 24 0 K after irradiation of 240 MGy while that of 22 0 K in beta'-ICl2 does not vary Taking account of the suppressed amplitude of the dicyanamide vibration modes in the infrared spectra of the irradiated kappa-Cl we suggest that X-ray irradiation modifies the anion structure related to the CN group which does not hold in beta -ICl2 (C) 2009 Elsevier B V All rights reserved