Abstract
The longitudinal and transverse ultrasound speeds and attenuation were measured in a MnSi single crystal in the temperature range of 2–40 K and magnetic fields up to 7 Tesla. The magnetic phase diagram of MnSi in applied magnetic field appears to depend on the experimental setups, which is related to a difference in demagnetization factors arising due to the disk shape of the sample. The magnetic phase transition in MnSi in zero magnetic field is signified by a quasidiscontinuity in the elastic constant, which varies significantly with magnetic field. It is notable that the region where the discontinuity almost vanishes closely corresponds to the extent of skyrmion phase along the magnetic to paramagnetic transition. This implies that the elastic constant is almost continuous through the transition from the skyrmion to paramagnetic phases. A recovery of the discontinuity of and enhanced sound absorption occur at the crossing of the phase transition line and the line of minima in . The powerful fluctuations at the minima of make the mentioned crossing point similar to a critical end point, where a second order phase transition meets a first order one.
2 More- Received 21 April 2015
- Revised 20 May 2015
DOI:https://doi.org/10.1103/PhysRevB.91.214402
©2015 American Physical Society