Effect of magnetic field on the intermediate phase in Mn$_{1-x}$Fe$_{x}$Si: spin-liquid vs. fluctuations scenario

We report results of the magnetic field influence on the chiral spin liquid state in Mn$_{1-x}$Fe$_x$Si single crystal with iron content $x=0.108$ in proximity of a hidden quantum critical point. The use of small angle neutron scattering data together with magnetic susceptibility measurements down to $0.4$ K and precise magnetoresistance measurements in the temperature range $2$–$20$ K in magnetic field up to $5$ T allowed us to construct the magnetic phase diagram of this compound in which at low magnetic fields $B<0.15$ T an intermediate phase with short-range magnetic order exists in a wide temperature range $0.62<T<9.1\,$K. It was found that the increase of magnetic field first results in a suppression of transition into spiral phase with long-range magnetic order at very low temperatures, and then induces a transition of the intermediate phase into a spin-polarized (ferromagnetic) phase with lowering temperature. The temperature of this transition $T_{\text{SP}}$ increases with magnetic field logarithmically, $T_{\text{SP}}\sim\log(B)$, and results in formation of a singular point on the magnetic phase diagram located at $T\sim8.5$ K and $B\sim3.5$ T, which may be either a triple or a critical point. The possible spin-liquid nature of the intermediate phase is discussed.