%0 journal article
%@ 1098-0121
%A Grigoriev, S.V.,Maleyev, S.V.,Okorokov, A.I.,Chetverikov, Y.O.,Eckerlebe, H.

%D 2006
%J Physical Review  B
%N 22
%P 224440 
%R doi:10.1103/PhysRevB.73.224440
%T Field-induced reorientation of the spin helix in MnSi near Tc
%U https://doi.org/10.1103/PhysRevB.73.224440
22 
%X The chiral spin fluctuations and the spiral structure of the single crystal MnSi has been studied by small angle polarized neutron scattering near Tc=29  K under applied field. A weak magnetic field applied along one of the <111> axes produces a single domain sample with the helix wave vector along the field. The 90° reorientation of the spin spiral from the [111] axis to [1[overline 1]0] axis is observed in the field range from 130 to 180  mT in the close vicinity to Tc. Further increase of the field above 180  mT restores the original orientation of the helix and leads to the induced ferromagnetic state at 350  mT. This observation clarifies the nature of the structural spin instability found in the H-T phase diagram of MnSi by other techniques. We explain this phenomenon as a result of competition of cubic anisotropy and the spin-wave Bose condensation provoked by the field perpendicular to the helix axis.