Influence of impurities on the phase transitions in chiral magnets: Monte Carlo calculations

Abstract

Using classical Monte Carlo simulation we investigate the evolution of the specific heat in chiral magnets with impurities. Our calculations are made in the framework of a spin lattice model and could be applicable to an analysis of the specific heat in transition-metal monosilicides ${\mathrm{Mn}}_{1\ensuremath{-}x}$(Fe,${\mathrm{Co})}_{x}\mathrm{Si}$ with increasing doping. We propose two tentative models for impurity positions in the lattice. In the first one, impurities substitute the regular transition-metal ions in a parent compound. The second one treats impurities as frozen spins placed into interstitial positions of the regular lattice and coupled with their nearest neighbors by random exchange interactions. In both models an increase of doping leads to a quick degradation of the magnetic phase transition, though an evolution of the hump anomaly is not similar. We provide a comparison of the behavior of the specific heat and Bragg scattering amplitude for these two models.