Heat capacity and thermal expansion of the itinerant helimagnet MnSi

Abstract

The heat capacity and thermal expansion of a high quality single crystal of MnSiwere measured at ambient pressure at zero and high magnetic fields. Thecalculated magnetic entropy change in the temperature range 0–30 K is less than0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A lineartemperature term dominates the thermal expansion coefficient in the range 30–150 K, whichcorrelates with an enhancement of the linear electronic term in the heat capacity. Asurprising similarity among the variations of the heat capacity, thermal expansioncoefficient and temperature derivative of the resistivity is observed through the phasetransition in MnSi. Specific forms of the heat capacity, thermal expansion coefficient andtemperature derivative of resistivity at the phase transition to a helical magnetic state near29 K are interpreted as the combination of sharp first-order features and broad peaks orshallow valleys of as yet unknown origin. The appearance of these broad satellites probablyhints at a frustrated magnetic state slightly above the transition temperature in MnSi.