Temperature dependence in the magnetization reversal process of DyFe2/YFe2exchange-coupled superlattices

X-ray magnetic circular dichroism (XMCD) measurements have been performed to study the magnetization reversal of a [DyFe2(5 nm)/YFe2(20 nm)]13 superlattice that exhibits a negative interface exchange coupling. By recording compound-specific hysteresis loops, we have shown a strong temperature dependence in this magnetization reversal process: below 150 K interface magnetic twists develop as expected predominantly in the softer YFe2 layers, whereas above 200 K the magnetization reversal first affects the harder DyFe2 compound. The sharp transition between these two regimes accounts for the variation of the coercive field, from a positive to a negative value. Different possible mechanisms for the first reversal of the hard compound are discussed.