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High pressure; Magnetic phase diagram; Helical order

MnSi is an itinerant ferromagnet with a long-wavelength helical modulation of the spin structure. Macroscopic measurements suggest that the ordering temperatureT_c is reduced with increasing pressure fromT_c = 30 K atp = 0 to zero at the critical pressurep_c = 14.6 kbar. Resistivity measurements show that MnSi enters a non-Fermi liquid state atp_c, which remains to be understood. Neutron scattering techniques have been used to investigate the magnetic structure at and abovep_c, i.e. triple-axis spectrometry and small angle neutron scattering. Surprisingly, sizeable quasi-static moments were found to survive to pressures considerably abovep_c. They are, however, organized in a highly unusual way such that the magnetic Bragg reflections are sharp in the longitudinal direction but are very broad in the transverse direction, implying a partial magnetic order that was never seen before.

L Pintschovius¹ D Reznik^{1 2} C Pfleiderer³ H v Löhneysen^{1 3}

1. Forschungszentrum Karlsruhe, IFP, P.O. Box 3640, Karlsruhe - D-76021, Germany
2. Laboratoire Léon Brillouin, CE-Saclay, Gif-sur-Yvette Cedex - F-91911, France
3. Physikalisches Institut, UniversitÄt Karlsruhe, Germany

Published

July 2004