The cubic noncentrosymmetric structure of the B20 compounds produces the helical ( homochiral) structure with the wave vector k(s) = 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 H-c2 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 k(s) and, second, makes its own contribution to the value of the critical field H-c2. We illustrate our findings taking an example of a transformation of the helix structure to the ferromagnet at x -> x(c) in the solid solutions Fe1-xCoxGe. We demonstrate that the mechanism of the transformation is realized via the competition between the cubic anisotropy and the Dzyaloshinskii-Moriya interaction.
|Number of pages||7|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2015|