Quantum SU (3)-ferrimagnet on triangular lattice

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 S = 1,1/2,1/2) , 1/2 , 1/2 ) SU (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 SU (3) algebra, the Hubbard operators representation of generators is used. Dependencies of the magnetic moments R and RL 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 / J of exchange integrals from different sublattices. It is established that for I/J / J << 1 the critical value D , 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 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 SU (3)-ferrimagnet is carried out and modification of the spectrum with change in the single-ion anisotropy is analyzed.