Magnetic phase diagram of doped MnSi

The noncentrosymmetric chiral structure of cubic \textit{B20} compound MnSi favors Dzyaloshinskii-Moria (DM) interaction ($D)$ where the broken inversion symmetry determines direction of $D$ and the strength of spin-orbit coupling determines the magnitude of $D$. This relatively weak DM interaction $D$ competes against the exchange interaction ($J)$ resulting in rather unusual long wavelength helimagnetism with the period set by the ratio ($J/D)$. Previous work has shown that both helimagnetic period ($\lambda )$ and the transition temperature ($T_{C})$ are reduced as a result of either Fe or Co substitutions on Mn site [1, and references therein]. Recently we have started to investigate the effect on the helimagnetic/Skyrmion structure and the transition temperature by chemical substitutions on the Si site. I will present our preliminary magnetization and neutron scattering results where we have found clear evidence of increase in both $T_{C}$ and helimagnetic period as a result of doping. The possible connection between carrier doping and the strength of DM interaction strength will be discussed. \begin{enumerate} \item Bauer, A., et al. "Quantum phase transitions in single-crystal Mn $_{1-\, x}$ Fe $_{x}$ Si and Mn $_{1-\, x}$ Co $_{x}$ Si: Crystal growth, magnetization, ac susceptibility, and specific heat."~\textit{Physical Review B}~82.6 (2010) . \end{enumerate}