ESR study of (C 5H 12N) 2CuBr 4

Abstract ESR studies at 9.27, 95.4, and 289.7 GHz have been performed on (C5H12N)2CuBr4 down to 3.7 K . The 9.27 GHz data were acquired with a single crystal and do not indicate the presence of any structural transitions. The high frequency data were collected with a polycrystalline sample and resolved two absorbances, consistent with two crystallographic orientations of the magnetic sites and with earlier ESR studies performed at 300 K . Below B C1 =6.6 T , our data confirm the presence of a spin singlet ground state.