Ge*

The kagome hexagonal compound Mn₃Ge is a room temperature non-collinear antiferromagnet with anomalous transport properties associated with electronic Weyl nodes near the chemical potential. The coupling of its electronic transports with magnetic order presents important technological opportunities for which, I will describe our experimental efforts to understand the magnetism of Mn₃Ge through neutron scattering techniques. Using polarized neutron diffraction, we show the magnetic order is a k=0 co-planar anti-chiral state with weak ferromagnetism described by a Γ₉ irreducible representation with magnetization remarkably aligned perpendicular to an applied field. Using time-of-flight neutron spectroscopy, we find three collective excitations above distinct Γ-point anisotropy gaps. These can be modeled as the normal modes of an anti-chiral triangular spin plaquette where an out-of-plane mode anti-crosses an optical phonon near 15-18 meV. Away from the zone center, magnetic excitations form a broad maximum near 75 meV with a half-width at half maximum of 25(5) meV indicative of itinerant magnetism. We develop a field theory of spin waves, which accurately describes the long wavelength magnetic properties, and use it to determine an effective low energy spin hamitonian for Mn₃Ge.