From spiral to ferromagnetic structure in B20 compounds: Role of cubic anisotropy

This is the authors' abstract. We don't add key points for this paper.

The cubic noncentrosymmetric structure of the B20 compounds produces the helical (homochiral) structure with the wave vector kₛ=D/J balanced by the competition of two interactions: the large ferromagnetic exchange interaction J and small antisymmetric Dzyaloshinskii-Moriya interaction D. The difference in the energies between the ferromagnetic collinear and helical states can be experimentally measured by the critical magnetic field Hc2 needed to transform the helix into the field-induced ferromagnet. We show that the cubic anisotropy, first, can limit the stability of the helix phase in the range of small kₛ and, second, makes its own contribution to the value of the critical field Hc2. We illustrate our findings taking an example of a transformation of the helix structure to the ferromagnet at x→xc in the solid solutions Fe_1-xCoₓGe. We demonstrate that the mechanism of the transformation is realized via the competition between the cubic anisotropy and the Dzyaloshinskii-Moriya interaction.