Threshold field for the de Almeida–Thouless transition line in Eu0.4Sr0.6S spin glass

Abstract
Measurements of the imaginary component of the ac magnetic susceptibility of a spherical sample of Eu0.4Sr0.6S at frequencies between 7 Hz and 5 kHz reveal that the temperature for the onset of hysteresis decreases as approximately Ha2/3 in an applied dc magnetic field Ha but only when the field exceeds a frequency‐dependent threshold H0( f). This threshold also marks the onset for nonlinearity in the real component of the susceptibility and thus delineates two regions of distinctly different dynamical response.