Neutron Scattering and µSR Studies of Spin Fluctuations in Frustrated Itinerant Magnets
Extensive measurements have been made of the spin dynamics of YMn2and its alloys, and of β-Mn and β-Mn-Al alloys, using a combination of inelastic neutron scattering and muon spin relaxation. The dynamical response measured by time-of flight neutron spectroscopy in YMn2alloys is strongly peaked at the characteristic wavevectors of the antiferromagnetic spin fluctuations. It appears that the wavevectors found in recent single crystal studies of YMn2are similar to those found in Monte Carlo simulations of localised moments in the antiferromagnetic pyrochlore lattice. In YMn2alloys the neutron linewidths are strongly correlated with the unit cell volume: substitution of Mn by Al expands the cell and decreases the linewidth, while substitutions of Sc for Y and Fe for Mn contract the cell and increase the linewidth. µSR measurements on β-Mn-Al alloys show a crossover from the Lorentzian to stretched exponential damping above 9% Al, the concentration at which the spin glass temperature begins to rise rapidly. This suggests a regime dominated by spin fluctuations below 9% Al and a regime with stable Mn moments above this composition.
KeywordsSpin Glass Inelastic Neutron Spin Fluctuation Inelastic Neutron Scattering Magnetic Phase Diagram
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