Magnetic transitions in the positional isomers (4-HOPNN and 2-HOPNN) of an organic nitronyl nitroxide radical using muon-spin rotation

摘要

The zero-field muon-spin rotation/relaxation technique has been used in the direct observation of spontaneous magnetic order below the Curie temperature of T-C similar to 500 mK in 2-hydroxyphenyl-alpha-nitronyl nitroxide (2-HOPNN) and two successive magnetic transitions in 4-hydroxyphenyl-alpha-nitronyl nitroxide (4-HOPNN) at T-C1 approximate to 700 and T-C2 similar to 100 mK. The different position of the hydroxyl group in these positional isomeric compounds causes different crystal packings and magnetic dimensionalities. The results reveal different magnetic transitions in these two a-nitronyl nitroxides radicals suggesting a 2D-3D magnetic crossover in 4-HOPNN. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 18]