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.
KeywordsHigh pressure Magnetic phase diagram Helical order
PACS Nos75.25.+z 75.40.-s
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