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

• Published in: Physical review. B, Condensed matter and materials physics Vol. 91; no. 22
• Main Authors: Grigoriev, S. V., Sukhanov, A. S., Maleyev, S. V.
• Format: Journal Article
• Language: English
• Published: 29-06-2015
• Subjects: Anisotropy; Competition; Condensed matter; Ferromagnetism; Germanium; Helical; Solid solutions; Transformations
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.91.224429

The cubic noncentrosymmetric structure of the B20 compounds produces the helical (homochiral) structure with the wave vector k sub()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 sub()cneeded 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 sub()sand, second, makes its own contribution to the value of the critical field H sub()c We illustrate our findings taking an example of a transformation of the helix structure to the ferromagnet at x [arrowright] x sub()cin the solid solutions Fe sub(1-)xCo sub()xGe. We demonstrate that the mechanism of the transformation is realized via the competition between the cubic anisotropy and the Dzyaloshinskii-Moriya interaction.