Physical properties of MnSi at extreme doping with Co: Quantum criticality

TL;DR

This study investigates how doping MnSi with Co affects its magnetic and thermal properties, revealing the destruction of the helical phase transition and the emergence of quantum critical behavior at low temperatures.

Contribution

It provides new insights into the effects of Co doping on MnSi, demonstrating the suppression of the helical phase transition and the persistence of quantum critical fluctuations.

Findings

Doping with Co destroys the helical phase transition in MnSi.

Helical fluctuation area persists above the transition temperature.

Quantum critical behavior observed as $C_p/T$ diverges at low T.

Abstract

The samples of (Mn$_{1-x}$Co$_x$)Si with $x=0.15$ and $x=0.17$ were grown and their physical properties: magnetization and magnetic susceptibility, resistivity and heat capacity were studied. The data analysis included also the previous results at $x=0.057, 0.063, 0.09$. The indicated doping MnSi with Co completely destroys the helical phase transition whereas basically saves the helical fluctuation area normally situated slightly above the phase transition temperature. This area spreading from $\sim$5 to 0 K is not changed much with doping and forms some sort of helical fluctuation cloud revealing the quantum critical properties: $C_p/T\rightarrow\infty$ at $T\rightarrow0$.