Abstract
Taking into account the results of LDA+U+SO-modeling of the electronic structure of Fe1-xCoxSi, temperature-prolonged magnetic phase transitions of the first order in strongly correlated alloys with a broken crystal structure of the B20 type are investigated. It is shown that such phase transitions are induced by concentration and thermodynamic fluctuations for compositions with 0.2<x<0.65 and are accompanied by a change in the sign of the mode-mode coupling parameter. In this case, an intermediate region appears between the long-range order phases and the paramagnetic phase, with the short-range spin order characterized by ferromagnetic and helicoidal spatial fluctuations. We have defined the intervals of external magnetic fields, at which skyrmion microstructures spatially limited by the crossover of helicoidal and ferromagnetic fluctuations appear in the considered region of the extended phase transition. The peculiarities of the temperature dependences of the magnetic susceptibility in an external magnetic field, characteristic of the appearance of skyrmions, are obtained.
Highlights
The crystal structure of helicoidal ferromagnets MnSi, Fe1-xCoxSi, Fe1-yMnySi, etc. belongs to the B20 structure type with the P213 space group, in which there is no inversion symmetry.1 The latter removes prohibition of the existence of the antisymmetric relativistic Dzyaloshinskii–Moriya (DM) exchange, the occurrence of which is one of the reasons for magnetic chirality
We have considered the main features of the concentration-temperature dependences of the magnetic properties of chiral ferromagnets Fe1-xCoxSi with the B20 crystal structure
The obtained temperature dependences of the magnetic susceptibility at various concentrations are in agreement with the experimental data in the region of the magnetic phase transition of the first and second order
Summary
The crystal structure of helicoidal ferromagnets MnSi, Fe1-xCoxSi, Fe1-yMnySi, etc. belongs to the B20 structure type with the P213 space group, in which there is no inversion symmetry. The latter removes prohibition of the existence of the antisymmetric relativistic Dzyaloshinskii–Moriya (DM) exchange, the occurrence of which is one of the reasons for magnetic chirality. In the region of magnetic phase transitions in these materials, the neutron diffraction experiment reveals an intermediate (between the helicoidal and paramagnetic phases) region of spin short-range order, in which fluctuations of the helix are observed.. In the region of magnetic phase transitions in these materials, the neutron diffraction experiment reveals an intermediate (between the helicoidal and paramagnetic phases) region of spin short-range order, in which fluctuations of the helix are observed.2 In this case, skyrmion microstructures appear in external magnetic fields, the nature of the formation of which remains unclear. On the basis of the obtained equations of magnetic state and expressions for irreducible spin correlators, we investigate ferromagnetic and helicoidal spatial fluctuations and spin microstructures that arise during a temperature-extended phase transition in Fe1-xCoxSi. We investigate the strongly correlated electronic system of Fe1-xCoxSi in the framework of the Hubbard Hamiltonian, extended by taking into account the difference in the intra-atomic Coulomb interactions at the sites occupied by Fe and Co atoms. Is the generating functional, which coincides with the partition function for the generating fields h′q equal to zero with q≠(0, q0)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
