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Glassiness and canted antiferromagnetism in three geometrically frustrated triangular quantum Heisenberg antiferromagnets with weak Dzyaloshinskii-Moriya interaction

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: M.A. Girtu, C.M. Wynn, W. Fujita, K. Awaga and A.J. Epstein

Editorial: Phys. Rev. B, 61, p.4117, 2000.


We report results of extensive magnetic studies of three triangular quantum
Heisenberg antiferromagnets (TQHAFs) with weak additional Dzyaloshinskii-Moriya interaction, Cu2(OH)3(CmH{2m+1}COO), m=7,9, and 11. Fits of the dc susceptibility data to high temperature series expansions are consistent with high temperature TQHAF behavior. At low
temperatures the deviations from the TQHAF predictions suggest a canted
antiferromagnetic type of ordering, consistent with the strong peak in the
second harmonic of the nonlinear ac susceptibility, which indicates the
development of a spontaneous moment. The frequency dependence of the linear ac susceptibility and the irreversibility in the field-cooled/zero-field-cooled
magnetization reveal spin glass-like behavior. Glassy behavior also is
suggested by the specific heat data, which show only a weak broad feature at
the transition. We propose that, instead of choosing between the resonant
valence bond or noncollinear Neel ground states expected for the ideal
TQHAF, these systems undergo, due to the additional Dzyaloshinskii-Moriya
interaction, a finite temperature phase transition to a state with both
Ising-like canted antiferromagnetic and glassy characteristics. The interplay
of Heisenberg exchange, causing frustration, and Dzyaloshinskii-Moriya
interaction, determining spin canting, leads to an unusual state in which order
and disorder appear to coexist.

Cuvinte cheie: quantum triangular antiferromagnet