Tricritical behavior in MnSi at nearly hydrostatic pressure

Abstract

AC magnetic susceptibility of a single crystal of MnSi was measured along the ferromagnetic phase-transition line up to a pressure of $0.8\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ created by compressed helium. The results show that the tricritical point is situated at much lower pressure and at significantly higher temperature (${P}_{\mathit{tr}}\ensuremath{\cong}0.355\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, ${T}_{\mathit{tr}}\ensuremath{\cong}25.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$) than was reported previously ($\ensuremath{\sim}1.2\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, $\ensuremath{\sim}12\phantom{\rule{0.3em}{0ex}}\mathrm{K}$). These observations put certain constraints on the origin of the tricritical point in MnSi.