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SUMMARY:Evolution of the magnitude of the exchange and Dzyaloshinskii-Mori
 ya interactions under pressure in chiral magnet MnSi
DTSTART;VALUE=DATE-TIME:20220829T164000Z
DTEND;VALUE=DATE-TIME:20220829T170000Z
DTSTAMP;VALUE=DATE-TIME:20220826T110111Z
UID:indico-contribution-3765@indico.stfc.ac.uk
DESCRIPTION:Speakers: Pierre Dalmas de Reotier (Univ. Grenoble Alpes)\nThe
  intermetallic compound MnSi exhibits a number of properties that have att
 racted strong interest. In particular it magnetically orders below 29.5 K 
 to an exotic long-pitch helical structure. This type of order is due to th
 e presence of the Dzyaloshinskii-Moriya interaction\, authorized by the ab
 sence of inversion symmetry in the crystal structure\, that coexists with 
 a dominant ferromagnetic exchange interaction.\nAs often observed in stron
 gly correlated magnets\, the properties of MnSi are strongly influenced by
  the application of a relatively modest pressure. The MnSi ordering temper
 ature decreases with pressure up to ~1.5 GPa\, above which value its groun
 d state is non-magnetic.\nHere we report on recent zero-field $\\mu$SR mea
 surements aimed at determining the evolution of the magnetic order under p
 ressure. Up to 1.3 GPa\, the high statistics asymmetry spectra can be anal
 ysed using the model derived a couple of years ago for the interpretation 
 of room pressure measurements [1]. Thanks to a prior determination of the 
 muon site and of the muon coupling parameters\, the parameters entering th
 e model are directly those of the magnetic structure.\nFor each pressure\,
  we find the ordered magnetic moment $m$ to decrease as $T^2$ from its low
  temperature value\, similar to earlier results obtained at room pressure 
 [2]. This decrease is the signature of the excitations of spin waves (heli
 magnons) as the temperature is raised. The quadratic temperature dependenc
 e reflects the form and anisotropy of the helimagnon dispersion relation. 
 From the slope of $m(T)$ vs $T^2$ we determine the two parameters of the d
 ispersion relation\, from which we quantitatively deduce the magnitude of 
 the exchange and Dzyaloshinskii-Moriya interactions at each pressure. Fina
 lly the spectra recorded at 1.44 GPa are discussed.\n[1] P. Dalmas de Reot
 ier et al\, Phys. Rev. B 93\, 144419 (2016).\n[2] A. Yaouanc et al\, Phys.
  Rev. Research 2\, 013029 (2020).\n\nhttps://indico.stfc.ac.uk/event/53/co
 ntributions/3765/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3765/
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