Systematic study of the itinerant ferromagnet MnSi at ambient and high hydrostatic pressures

The intermetallic compound MnSi experiences a phase transition at a temperature slightly below 30K, acquiring helical magnetic structure and becoming a weak itinerant ferromagnet. We have carried out precise resistivity and ac susceptibility measurements of MnSi single crystals across the phase transition line at ambient and high pressures, using a compressed helium technique. In addition, heat capacity, thermal expansion and dc magnetic susceptibility were measured at ambient pressure. Conclusions drawn from these experiments propose that the phase transition in MnSi is of first order at ambient pressure and may become continuous at high pressure and low temperature. (C) 2007 Elsevier B.V. All rights reserved.