Magneto-elastic interaction in cubic helimagnets with B20 structure.

The magneto-elastic interaction in cubic helimagnets with B 20 symmetry is considered. It is shown that this interaction is responsible for a negative contribution to the square of the spin-wave gap Δ and it alone appears to disrupt the assumed helical structure. It is suggested that competition between the positive part of Δ(I)(2), which stems from magnon-magnon interaction, and its negative magneto-elastic part leads to the quantum phase transition observed at high pressure in MnSi and FeGe.

Crystal handedness and spin helix chirality in Fe1-xCoxSi.

We show, with the help of polarized neutrons, that the cubic magnets Fe1-xCoxSi with Dzyaloshinskii-Moriya interaction can be switched between left (for x=0.1, 0.15) and right (for x=0.

Spin-wave interaction and renormalization of magnetic anisotropy in 2D antiferromagnets.

The renormalization of the magnetic anisotropy is investigated in 2D easy-axis antiferromagnets using 1/S expansion. It was shown that in the spin-wave gap Delta appears as the 1/S2 infrared divergent correction which becomes large at T>Delta and demands analysis of the full 1/S expansion. Qualitative consequences of this gap renormalization are discussed in relation to the AFR and neutron scattering experiments.