Pressure Induced Crossover of the Magnetic Transition from Second to First Order near the Quantum Critical Point in {{MnSi}}

The magnetic ordering transition temperature in MnSi decreases with increasing pressure and tends towards absolute zero near 15 kbar. As the critical pressure is approached, we observe a crossover from a conventional transition of second order to one of weak first order. The crossover point is found to be near a minimum in the inverse susceptibility as a function of temperature. A qualitative description of this behaviour is given in terms of a temperature dependent renormalisation of the coefficients in a sixth order Landau expansion for the free energy.     «

The magnetic ordering transition temperature in MnSi decreases with increasing pressure and tends towards absolute zero near 15 kbar. As the critical pressure is approached, we observe a crossover from a conventional transition of second order to one of weak first order. The crossover point is found to be near a minimum in the inverse susceptibility as a function of temperature. A qualitative description of this behaviour is given in terms of a temperature dependent renormalisation of the coeffi...     »