Neutron scattering study of the itinerant-electron magnet YMn₂

Neutron scattering with polarized beam analysis has been used to study the magnetic properties of the antiferromagnet YMn₂ (T_N≃100 K). Previous susceptibility, NMR relaxation, and preliminary neutron measurements indicate a transition from a local-moment magnet in the ordered phase to an itinerant-electron magnet above T_N. We present a detailed analysis of magnetic-scattering data measured for temperatures ranging from T=10 K to T=600 K. The analysis includes energy integration of the paramagnetic response, simple model calculations of the measured powder average, and absolute calibration of the cross sections. The amplitude of the local magnetic moment per Mn atom is extracted and shown to drop by more than ∼30% at T_N and to slowly increase again with increasing temperature, and up to 6T_N strong antiferromagnetic correlations are found to persist. This behavior is consistent with recent theories for itinerant-electron magnetism.