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 temperature 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 constant of -12(2) K. At low temperature we find 1D magnetic behaviour evidenced by a broad maximum in the susceptibility. Below 4.9 K weak ferromagnetism is detected which is attributed to a canting of the antiferromagnetic sublattices of about 0.13-degrees. Strong nonresonant microwave absorption appears below 4 K which exhibits a hysteresis when measured in a small scanned external field. Possible origins of the weak ferromagnetism and the nonresonant microwave absorption are discussed.