Hysteretic resistance spikes at transitions between quantum Hall ferromagnets in AlAs 2D electrons

We report hysteretic resistance spikes at transitions between quantum Hall ferromagnets in AlAs two-dimensional electrons. The observed magnetic hysteresis depends sensitively on the electron occupation of the two energy levels crossing at the transition. Temperature-dependent measurements show that the resistance spikes at the transition are not activated, in contrast to the resistance minima away from the transition, which follow an Arrhenius behavior.