THEORETICAL-STUDIES OF MAGNETIC-INTERACTIONS IN 2',5'-DIHYDROXYPHENYLNITRONYL NITROXIDE CRYSTAL

In order to investigate the ferromagnetic interaction in the alpha pha se of 2'5'-dihydroxyphenyl nitronyl nitroxide (HQNN), semiempirical an d ab initio molecular orbital calculations were carried out for severa l pair models of HQNN molecules extracted from the crystal structure. It was shown that the effective exchange interaction (J(ab)) for the n earest neighbor molecules is ferromagnetic, being in agreement with th e experimental result. The hydroxyl groups and the methyl groups contr ibute to the ferromagnetic interaction in the a phase of HQNN crystal.