ZF mu SR of an organic weak ferromagnet with T-c=35 K

Zero-field mu SR has been used to study the internal field in the beta crys tal phase of the dithia-diazolyl molecular radical p-NC(C-6 F-4) (CNSSN), w hich is a canted antiferromagnet showing spontaneous magnetisation below 35 K. Two distinct frequencies are resolved in the zero-field muon spin rotat ion 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 t he spin structure is along the b-axis. Muon spin relaxation below the trans ition follows the power law expected for two magnon scattering along with s ome sharper features near the transition suggesting strong magnon-phonon in teraction. (C) 2000 Elsevier Science B.V. All rights reserved.