Low temperature magnetization of the S = 1/2 kagome antiferromagnet ZnCu3 (O H) 6CL 2

Abstract : The dc magnetization of the unique S= 1/ 2 kagome antiferromagnet Herbertsmithite has been measured down to 0.1 K. No sign of spin freezing is observed in agreement with former SR and ac-susceptibility results. The low temperature magnetic response is dominated by a defect contribution which exhibits an energy scale 1 K, likely reflecting the coupling of the defects. The defect component is saturated at low temperature by H8 T applied magnetic fields which enables us to estimate an upper bound for the nonsaturated intrinsic kagome susceptibility at T=1.7 K.