EXPERIMENTAL STUDY OF MAGNETIC PHASE TRANSITION IN THE ITINERANT HELIMAGNET MnSi
Stishov S.M., Petrova A.E., Khasanov S., Panova G.Kh., Shikov A.A., Lashley J.C., Wu D., Lograsso T.A.

Received: September 16, 2007

PACS: 75.30.Kz, 75.40.Cx, 77.80.Bh

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Magnetic susceptibility, heat capacity, thermal expansion and resistivity of a high-quality single crystal of MnSi were carefully studied at ambient pressure. The calculated magnetic entropy change in the temperature range 0-30 K is less than 0.1R, the low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates behavior of the thermal expansion coefficient in the range 30-150 K, which correlates with great enhancement of the linear electronic term in the heat capacity. Surprising similarity between variation of the heat capacity, the thermal expansion coefficient, and the temperature derivative of resistivity through the phase transition in MnSi is observed. Specific forms of the heat capacity, thermal expansion coefficient, and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as a combination of sharp first-order features and broad peaks or shallow valleys of yet unknown origin. The appearance of these broad satellites probably hints at the frustrated magnetic state in MnSi slightly above the transition temperature. Present experimental findings question current views on the phase diagram of MnSi.