Entropic signatures of the skyrmion lattice phase in MnSi_1-xAl_x and Fe_1-yCo_ySi.

Cubic B20 magnets such as MnSi, (Fe, Co)Si host magnetic skyrmion lattice over a small range of temperature and magnetic fields. Although the qualitative features of the magnetic phase diagram look similar for MnSi and Fe_1-yCo_ySi, there are some differences in the nature of magnetic transition due to the effects of disorder and the difference in the dynamical behavior of spins. We compare MnSi and Fe_1-yCo_ySi based on the change in magnetic entropy during conical to magnetic skyrmion lattice transition. Our results indicate that despite qualitative similarities in the magnetic phase diagrams, the entropic signatures related to such topological transition are significantly reduced in Fe_1-yCo_ySi due to the effect of disorder and the differences in spin dynamical behavior.