Quantum SU(3)-ferrimagnet on triangular lattice

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


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 (�=1,1/2,1/2��(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 ��(3) algebra, the Hubbard operators representation of generators is used. Dependencies of the magnetic moments  and �� (for spin-1/2 and spin-1 sublattices respectively), the total magnetic moment , as well as the quadrupole moment, on the anisotropy parameter  are calculated at zero temperature and different ratios �/� of exchange integrals from different sublattices. It is established that for �/�≪1 the critical value ��, at which the system enters the quadrupole antiferromagnetic phase, can be much smaller than both  and . Besides, with an increase in  from zero to �� the total moment  can change its direction several times via taking zero value. Classification of four branches of the spin-wave excitation spectrum of the ��(3)-ferrimagnet is carried out and modification of the spectrum with change in the single-ion anisotropy is analyzed.