Effect of interlayer interactions and lattice distortions on the magnetic ground state and spin dynamics of a geometrically frustrated triangular-lattice antiferromagnet

We investigate the effects of interlayer interactions and lattice distortions on the noncollinear ground state and spin dynamics of a geometrically frustrated triangular-lattice antiferromagnet with implications for the multiferroic phase of doped CuFeO2, where both lattice distortions and anisotropy introduce anharmonic components into the spin ground state. In contrast to the single turn angle of a simple spiral, the turn angles of the predicted ground state are distributed about Δ θ1 and Δ θ2. Using a Holstein-Primakoff expansion, we show that distinct features in the spin dynamics are associated with the anharmonic components of the spin ground state, which have recently been observed in Ga-doped CuFeO2.