Domain wall structure and the properties of the coexistence phase in ferromagnetic superconductors HoMo6S8 and HoMo6Se8

In the framework of Ising ferromagnetic model the temperature dependence of the domain wall surface energy is studied. The obtained results are used to calculate the temperature dependence of the wave vector of the oscillatory magnetic structure in the coexistence phase of ferromagnetic superconductor HoMo6Se8. The estimate of the exchange interaction of localized moments and electrons explains why the coexistence phase survives on cooling down to zero temperature in HoMo6Se8 while the reentrant transition into the normal ferromagnetic phase takes place in HoMo6Se8. (author)