Antiferromagnetic resonance in tetramethyltetrathiafulvalene bromide [(TMTTF)Br2]

Observation of antiferromagnetic resonance in tetramethyltetrathiafulvalene bromide [(TMTTF)Br2] shows that the semiconducting ground state is antiferromagnetic, with a Néel temperature of 13±1 K. Two modes are observed as a function of magnetic field, for orientations near the easy (b) axis, at a fixed frequency of 9.3 GHz. At 4.2 K the zero-field modes are estimated to have frequencies of 11.7 and 18.2 GHz (4.3 and 6.6 kOe). © 1982 The American Physical Society.