COEXISTENCE OF GLASSINESS AND CANTED ANTIFERROMAGNETISM IN TRIANGULARQUANTUM HEISENBERG ANTIFERROMAGNETS WITH WEAK DZYALOSHINSKII-MORIYA INTERACTION

We present magnetic studies of three triangular quantum Heisenberg ant iferromagnets (TQHAF's) with weak additional Dzyaloshinskii-Moriya int eraction, Cu-2(OH)(3)(CmH2m+1COO), m=7, 9, and 11. Fits of the de susc eptibility data to high-temperature series expansions agree with high- temperature TQHAF behavior. At low temperatures the deviations from th e TQHAF predictions suggest a canted antiferromagnetic type of orderin g, while the strong peak in the second harmonic of the nonlinear ac su sceptibility indicates the development of a spontaneous moment. The fr equency dependence of the linear ac susceptibility and the irreversibi lity in the field-cooled/zero-field-cooled magnetization show that fru stration is strong enough to cause glassiness. We propose that the int erplay of Heisenberg and Dzyaloshinskii-Moriya exchanges leads to the unusual coexistence of glassiness and canted antiferromagnetism in the se geometrically frustrated systems.