Sergei Stishov (Troitsk)

June 25, 2019 @ 1:30 pm – 2:30 pm

Room B-131 Physics, Stony Brook University.  Tuesday June 25, 1:30 pm.  host: PBA

Physical properties of  (Mn 0.85 Fe 0.15)Si along the critical trajectory

A.E. Petrova and S.M. Stishov

Institute for High Pressure Physics of RAS, Troitsk, Moscow, Russia

Dirk Menzel

Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, D-38106 Braunschweig, Germany

The magnetic phase transition temperature in the helical magnet MnSi decreases with pressure and practically reaches zero value at  ~15 kbar. However a nature of this transition at zero temperature and high pressure is still a subject of controversial interpretations. Early it was claimed an existence of tricritical point on the phase transition line that might result in a first order phase transition in MnSi at low temperatures, preventing observation a quantum critical point in MnSi. On the other hand some experimental works and the recent Monte-Carlo calculations may indicate a strong influence of inhomogeneous stress arising at high pressures and low temperatures on characteristics of phase transitions that could make any experimental data not entirely conclusive.  In this situation it would be appealing to use a different approach to discover a quantum criticality in MnSi, for instance, making use doping as a control parameter. The results of studying the magnetization, specific heat and thermal expansion of a single crystal with nominal composition Mn 0.85 Fe 0.15 Si  show that the trajectory corresponding to the present composition of (MnFe)Si is a critical one, i.e. approaching quantum critical point at lowering temperature, but some properties may feel the cloud of helical fluctuations bordering the phase transition line.



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