Determination of the magnetic structure of Mn₃Sn using generalized neutron polarization analysis

Abstract

The newly developed technique of generalized polarization analysis has been used to re-examine the triangular magnetic structure of Mn3Sn. The magnitude and direction of the polarization of neutrons scattered by some mixed magnetic and nuclear Bragg reflections at 200 K have been measured for a range of different incident polarization directions using a zero-field polarimeter. The results have been used to discriminate between different models which have been proposed for the magnetic structure. The analysis shows unambiguously that a structure allowing three trigonal domains is necessary to account for the scattered polarizations. Of the models suggested up to now only the 'inverse triangle' structure satisfies this criterion. The manganese moment was determined to be 3.00(1) mu B much larger than the value (1.78 mu B) given by earlier measurements of the flipping ratios in an applied field. On cooling below 50 K the polarization analysis gave evidence for a transition to a magnetic structure with a significant ferromagnetically aligned moment parallel to (001).