Dzyaloshinskii-Moriya interaction in LiCu$_2$O$_2$
ORAL
Abstract
The far-infrared optical spectrum of the spin 1/2 helimagnet LiCu$_2$O$_2$ was investigated in magnetic fields up to 14Tesla. In the paramagnetic state a spin resonance line was observed corresponding to a $g$-factor of about 2. The resonance broadens and practically disappears around the phase transition temperature of T=25K, but it is recovered at lower temperatures at a new position. The 2.5K field dependence of the spin susceptibility and resonance frequency is characteristic of a magnetically ordered system, where the Dzyaloshinskii-Moriya interaction causes a finite gap of 1.5meV in the spin wave spectrum at q=0.
*Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.
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