Magnetic resonance in the ordered phases of the two-dimensional frustrated quantum magnet CS_2CuCl_4

摘要

The temperature evolution of electron spin resonance is studied upon cooling the crystal samples of Cs_2CuCl_4 through the Neel point 0.62 K. A coexistence of the high-frequency spinon-type resonance developed in the spin-liquid phase and of the low-frequency antiferromagnetic resonance was found in the ordered phase. The low-frequency magnetic resonance spectrum in the low-field range has two gapped branches and corresponds well to the spectrum of spin excitations of a planar spiral spin structure with two axes of the anisotropy. The field-induced phase transitions result in a more complicated low-frequency spectrum.