Quantum SU(3)-ferrimagnet on triangular lattice

Martynov, A.S., Dzebisashvili, D.M.// Journal of Magnetism and Magnetic Materials//

https://doi.org/10.1016/j.jmmm.2024.171906

Manifestations of quantum effects in the macroscopic properties of frustrated magnets keep attracting considerable interest. We have formulated and studied a simple model of a three-sublattice mixed-spin ( $S = 1, 1 / 2, 1 / 2$ ) $S U (3)$ -ferrimagnet on triangular lattice in which the strong quantum fluctuations are developed due to combined effect of frustrated exchange bonds, reduced dimensionality and a single-ion easy-plane anisotropy in the spin-1 sublattice. To account correctly for the $S U (3)$ algebra, the Hubbard operators representation of generators is used. Dependencies of the magnetic moments $R$ and $R_{L}$ (for spin-1/2 and spin-1 sublattices respectively), the total magnetic moment $M$ , as well as the quadrupole moment, on the anisotropy parameter $D$ are calculated at zero temperature and different ratios $I / J$ of exchange integrals from different sublattices. It is established that for $I / J ≪ 1$ the critical value $D_{c}$ , at which the system enters the quadrupole antiferromagnetic phase, can be much smaller than both $I$ and $J$ . Besides, with an increase in $D$ from zero to $D_{c}$ the total moment $M$ can change its direction several times via taking zero value. Classification of four branches of the spin-wave excitation spectrum of the $S U (3)$ -ferrimagnet is carried out and modification of the spectrum with change in the single-ion anisotropy is analyzed.