Observation of weak ferromagnetism in organic verdazyl radical crystal, p-CyDpTV

Magnetic property of 3-(4-cyanophenyl)-1,5-diphenyl-6-thioxoverdazyl (p-CyDpTV) radical crystal has been studied in the temperature range of 0.05–300 K in external magnetic fields 3, 11, 30, and 100 Oe by using SQUID magnetometer. Weak ferromagnetic behavior was observed at TN = 0.41 K. Below TN, the spontaneous magnetization Ms(T) increased rapidly, reaching a maximum of 31.1 emu/mol at 0.05 K. Spin-canting angle was estimated to be 0.32° at 0.05 K. Near TN, M s (T) ∝ [1 − ( T T N )] β with the critical exponent of β = 0.36, in agreement with that expected for an isotropic three-dimensional (3D) Heisenberg spin system.