Itinerant Antiferromagnetism in FeGe_2

TL;DR

This study investigates the magnetic phase diagram and spin dynamics of FeGe_2, revealing incommensurate and commensurate phases, and uncovers quasi-one-dimensional magnetic behavior through neutron scattering experiments.

Contribution

It provides detailed measurements of spin wave dispersion in FeGe_2, highlighting its quasi-one-dimensional magnetic dynamics and phase behavior under magnetic fields.

Findings

Incommensurate and commensurate magnetic phases identified.

Magnetic field reduces incommensurate phase stability.

Spin wave dispersion mapped up to 400 meV along the c-axis.

Abstract

FeGe_2, and lightly doped compounds based on it, have a Fermi surface driven instability which drive them into an incommensurate spin density wave state. Studies of the temperature and magnetic field dependence of the resistivity have been used to determine the magnetic phase diagram of the pure material which displays an incommensurate phase at high temperatures and a commensurate structure below 263 K in zero field. Application of a magnetic field in the tetragonal basal plane decreases the range of temperatures over which the incommensurate phase is stable. We have used inelastic neutron scattering to measure the spin dynamics of FeGe_2. Despite the relatively isotropic transport the magnetic dynamics is quasi-one dimensional in nature. Measurements carried out on HET at ISIS have been used to map out the spin wave dispersion along the c-axis up the 400 meV, more than an order of magnitude higher than the zone boundary magnon for wavevectors in the basal plane.