Spin nematic and orthogonal nematic states in S=1 non-Heisenberg magnet

Phases of S=1 non-Heisenberg magnet at various relationships between the exchange integrals are studied in the mean-field limit at zero temperature. It is shown that four phases can be realized in the system under consideration: the ferromagnetic, antiferromagnetic, nematic, and the orthogonal nematic states. The phase diagram is constructed. It is shown that the phase transitions between the ferromagnetic phase and the orthogonal nematic phase and between the antiferromagnetic phase and the orthogonal nematic phase are the degenerated first-order transitions. For the first time the spectra of elementary excitations in all phases are obtained within the mean-field limit.

► We investigated phases of S=1 non-Heisenberg magnet.
► Found four phases: ferromagnetic, antiferromagnetic, nematic, and orthogonal nematic.
► The phase diagram is determined.
► The spectra of elementary excitations are obtained in all phases for the first time.