Zero-field muon spin rotation study on TEMPO-based magnets, Ar-CHN-TEMPO

Abstract Long-range magnetic orderings are demonstrated by zero-field muon spin rotation/relaxation measurements on the genuine organic free radical crystals, 4-( p -chlorobenzylideneamino)-, 4-( p -phenylbenzylideneamino)-, and 4-(benzylideneamino)-TEMPOs (TEMPO=2,2,6,6-tetramethylpiperidin-1-yloxyl) with T C values of 0.28, 0.22, and 0.17 K, respectively, and 4-(4-pyridylmethyleneamino)-TEMPO with T N of ≈0.07 K. From comparison between the crystal structures and internal fields at the muon sites, dominant two-dimensional ferromagnetic interaction is confirmed and inter-sheet dipolar interaction is proposed for bulk magnetism.