WEAK FERROMAGNETISM AND MAGNETICALLY MODULATED MICROWAVE-ABSORPTION AT LOW MAGNETIC-FIELDS IN 1,3,5-TRIPHENYL-6-OXOVERDAZYL

The magnetic susceptibility and microwave properties of powder samples of 1,3,5-triphenyl-6-oxoverdazyl were investigated between room tempe rature and 1.8 K. The high-temperature susceptibility follows a Curie- Weiss law with a Curie constant of 0.38(1) emu K mol-1 and a Weiss con stant of -12(2) K. At low temperature we find 1D magnetic behaviour ev idenced by a broad maximum in the susceptibility. Below 4.9 K weak fer romagnetism is detected which is attributed to a canting of the antife rromagnetic sublattices of about 0.13-degrees. Strong nonresonant micr owave absorption appears below 4 K which exhibits a hysteresis when me asured in a small scanned external field. Possible origins of the weak ferromagnetism and the nonresonant microwave absorption are discussed .