Diffusion-limited kinetics of the antiferromagnetic to ferrimagnetic λ-transition in Fe1-xS

Fe1-xS (0.08 <= x <= 0.11) exhibits a simultaneous magneto-structural "lambda-transition" at approximately 200 degrees C. Time-dependent magnetization measurements demonstrate the lambda-transition can be accurately modeled by a stretched exponential function, consistent with a nucleation-free, continuous reordering of the vacancy-bearing sublattice. The experimental result is supported by kinetic Monte Carlo simulations that confirm the activation energy for the transition to be 1.1 +/- 0.1 eV-representing the iron vacancy migration energy in ordered Fe1-xS. A mechanistic understanding of the lambda-transition enables potential functional uses of Fe1-xS such as thermally activated magnetic memory, switches, or storage. (C) 2015 AIP Publishing LLC.