Pressure Collapse of the Magnetic Ordering in MnSi via Thermal Expansion

Abstract

The itinerant quasi-ferromagnetic metal MnSi has been studied by detailed thermal expansion measurements under pressures and magnetic fields. A sudden decrease of the volume at the critical pressure Pc ~1.6 GPa has been observed and is in good agreement with the pressure variation of the volume fraction of the spiral magnetic ordering. This confirms that the magnetic order disappears by a first order phase transition. The energy change estimated by the volume discontinuity on crossing Pc is of similar order as the Zeeman energy of the transition from the spiral ground state to a polarized paramagnetic one under magnetic field. In contrast to the strong pressure dependence of the transition temperature, the characteristic fields are weakly pressure dependent, indicating that the strength of the ferromagnetic and the Dzyaloshinskii-Moriya interactions do not change drastically around Pc. The evaluated results of the thermal expansion coefficient and the magnetostriction are analyzed thermodynamically. The Sommerfeld coefficient of the linear temperature term of the specific heat is enhanced just below Pc. The magnetic field-temperature phase diagrams in the ordered and paramagnetic phases are also compared. Comparison is made with other heavy fermion compounds with first order phase transition at 0 K.

9 pages, 13 figures, accepted to be published in JPSJ

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Cited by in corpus (6)

• Tricritical point and wing structure in the itinerant ferromagnet UGe2
• Effect of Negative Pressure on the Prototypical Itinerant Magnet MnSi
• Third law of thermodynamics and the shape of the phase diagram for systems with a first-order quantum phase transition
• Absence of magnetic phase separation in MnSi under pressure
• Physical properties of (Mn 0.85 Fe 0.15) Si along the critical trajectory
• On the robustness of the MnSi magnetic structure determined by muon spin rotation