Amorphous YFe2—A concentrated spin glass

Abstract

Magnetic susceptibility, Mössbauer, and neutron scattering studies of the same alloy sample all indicate that amorphous YFe2 (a-YFe2) exhibits spin-glass behavior with a truly thermodynamic spin-glass transition at TS.G.=58K. These studies show that spin-glass behavior can persist to quite high magnetic concentrations in an amorphous alloy system which is dominated by competing ferromagnetic and antiferromagnetic exchange interactions. At a lower temperature of T?20K, the susceptibility versus T curve shows a break and the coercive field is anomalous. We interpret this phenomenon near T=20K as arising from magnetic ’’blocking’’ of individual spins or regions of correlated spins which persist below TS.G.. This produces a cluster-freezing-type ’’pseudo-transition’’ which is merely a manifestation of the slowing down of spin fluctuations to a time interval comparable with the experimental susceptibility measurement time. The temperature dependence of the spin-glass order parameter is obtained from the susceptibility results and is in close agreement with data generated by Monte-Carlo simulations.