Evolution of helimagnetic correlations when approaching the quantum critical point of Mn1-xFexSi
C Pappas (TU Delft - RST/Neutron and Positron Methods in Materials)
A.O. Leonov (Hiroshima University)
Lars Johannes Bannenberg (TU Delft - RID/TS/Instrumenten groep)
P Fouquet (Institut Laue Langevin)
T. Wolf (Karlsruhe Institut für Technologie)
F Weber (Karlsruhe Institut für Technologie)
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Abstract
We present a comprehensive investigation of the evolution of helimagnetic correlations in Mn1−xFexSi with increasing doping. By combining polarized neutron scattering and high resolution neutron spin echo spectroscopy we investigate three samples with x = 0.09, 0.11, and 0.14, i.e., with compositions on both sides of the concentration x∗∼0.11 where the helimagnetic Bragg peaks disappear and between x∗ and the quantum critical concentration xC∼0.17, where TC vanishes. We find that the abrupt disappearance of the long range helical periodicity at x∗ does not affect the precursor fluctuating correlations. These build up with decreasing temperature in a similar way as for the parent compound MnSi. Also the dynamics bears strong similarities to MnSi. The analysis of our results indicates that frustration, possibly due to achiral Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, increases with increasing Fe doping. We argue that this effect explains both the expansion of the precursor phase with increasing x and the abrupt disappearance of long range helimagnetic periodicity at x∗.
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