One-dimensional regular isotropic heisenberg antiferromagnetism in an organic radical p-diethylaminophenyl nitronyl nitroxide [DEAPNN]: Observation of spin-flop at high field

The magnetic properties of the organic radical p-diethylaminophenyl nitronyl nitroxide (DEAPNN; 2-(4'-diethylaminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-N-oxide) have been investigated. The magnetization isotherms of DEAPNN measured up to 20.5 T at 1.7 and 4.2 K show a spin-flop phenomenon characteristic of one-dimensional regular isotropic Heisenberg antiferromagnetism. The magnetic susceptibility of DEAPNN is well interpreted by the Heisenberg antiferromagnetism in the whole temperature range of 2–300 K. The exchange coupling constant is determined to be J/k = -2.45 K based on the spin Hamiltonian H = -2JΣS_iS_{i + 1}.