Induced by the pressure and the spin fluctuations the phase transitions in chiral itinerant ferromagnetics (for example MnSi)

Abstract

In the framework of the spin-fluctuation theory, a magnetic (p-T)-diagram of strongly correlated band ferromagnets with the Dzyaloshinsky-Moriya interaction is considered. The resulting expression for the free energy functional contains pressure-dependent magnetic, electronic, and spin-fluctuation terms, which are self-consistent with each other. The conditions for the minimum of free energy and electroneutrality are considered at various pressures in the model of the electronic structure obtained for MnSi in result of GGA + U + SO calculations. A crossover of a first-order phase transition and a quantum transition is obtained, which leads to the appearance of a chiral spin liquid. The boundary point (T0, p0) at which the chiral fluid disappears is determined. The quantum transition of a ferromagnetic spin spiral into the phase of vortex spin microstructures coexistence with fixed spin chirality, which arises below the temperature of the boundary point, is considered. At higher pressures, chiral paramagnetism occurs.