ZF μSR of an organic weak ferromagnet with Tc=35 K

Zero-field mu SR has been used to study the internal field in the beta crystal phase of the dithia-diazolyl molecular radical p-NC(C-6 F-4) (CNSSN), which is a canted antiferromagnet showing spontaneous magnetisation below 35 K. Two distinct frequencies are resolved in the zero-field muon spin rotation signal, which have been assigned to muon states bonded at two different sites on the CNSSN ring. The muon data shows that the easy direction for the spin structure is along the b-axis. Muon spin relaxation below the transition follows the power law expected for two magnon scattering along with some sharper features near the transition suggesting strong magnon-phonon interaction. (C) 2000 Elsevier Science B.V. All rights reserved.