2 research outputs found
Stability of the skyrmion lattice near the critical temperature in cubic helimagnets
The phase diagram of cubic helimagnets near the critical temperature is
obtained from a Landau-Ginzburg model, including fluctuations to gaussian
level. The free energy is evaluated via a saddle point expansion around the
local minima of the Landau-Ginzburg functional. The local minima are computed
by solving the Euler-Lagrange equations with appropriate boundary conditions,
preserving manifestly the full nonlinearity that is characteristic of skyrmion
states. It is shown that the fluctuations stabilize the skyrmion lattice in a
region of the phase diagram close to the critical temperature, where it becomes
the equilibrium state. A comparison of this approach with previous computations
performed with a different approach (truncated Fourier expansion of magnetic
states) is given.Comment: 6 pages, 6 color figure
Thermal fluctuations in the conical state of monoaxial helimagnets
The effect of thermal fluctuations on the phase structure of monoaxial
helimagnets with external magnetic field parallel to the chiral axis is
analyzed by means of a saddle point expansion of the free energy. The phase
transition that separates the conical and forced ferromagnetic phases is
changed to first order by the thermal fluctuations. In a purely monoaxial
system the pitch of the conical state remains independent of temperature and
magnetic field, as in mean field theory, even when fluctuations are taken into
account. However, in presence of weak Dzyaloshinskii-Moriya interactions in the
plane perpendicular to the chiral axis, thermal fluctuations induce a
dependence of the pitch on temperature and magnetic field. This may serve to
determine the nature of magnetic interactions in such systems.Comment: 9 pages, 4 figure