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

Abstract

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 CuFeO 2 , 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 ⌬ 1 and ⌬ 2 . 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 CuFeO 2 .

Electric polarization along thecaxis in the ferroelectric helimagnetic phase ofCuFe1−xGaxO2

“…This is because the antiferromagnetic nearestneighbor (NN) superexchange interaction is weakened by decreasing the Fe-O-Fe bonding angle, and vice versa, and therefore the above-mentioned changes in the three Fe-O-Fe bonding angles can relieve the geometrical frustration. The resulting changes in the NN interaction were indeed observed in the previous inelastic neutron scattering studies on the 4SL and FE-ICM phases [39][40][41]. We found that the atomic displacements described by model III are in good agreement with this scenario.…”

“…As mentioned above, the existence of the in-plane atomic displacements is consistent with the previous studies [34,[39][40][41], and is naturally explained in terms of the "magnetostriction model," in which the bonding angles and/or the distance between the two magnetic Fe 3+ change with the values of S i · S j for each bond. On the other hand, we do not have a clear explanation for the mechanism of the atomic displacements along the c axis thus far.…”

Magnetic interactions in the multiferroic phase of CuFe1−xGaxO2Nakajima1, Mitsuda2, Haraldsen3 et al. 2012Phys. Rev. B182110View full textAdd to dashboardCite

“…Ref. 9 18 we started from the Hamiltonian used in the previous calculation for the multi-domain spectra in the multiferroic phase: 9,10…”

“…7,8 Recent theoretical studies by Haraldsen et al have pointed out that the turn angles of the screw-type helical arrangement of the spins have anharmonicity. 9,10 To elucidate how a small amount of nonmagnetic substitution changes the magnetic ground state of this system, it is important to determine the Hamiltonian parameters in both of the 4SL and multiferroic phases. In a previous study, Ye et al have performed inelastic neutron scattering measurements on CFO to determine the parameters in the 4SL phase.…”

Suppression of Standing Spin Waves in Low-Dimensional Ferromagnets

“…Additional dissipation mechanisms, most notably in the form of Stoner excitations at higher values of q [15,16] exacerbate the suppression to the extent that in practice all trace of these modes is lost in experiment. Given the rich spin dynamics of bulk systems characterized by noncollinear ground states [32,33], we suggest their thin film equivalents as a promising area for future study.…”