Temperature dependence of the training effect in exchange coupled ferromagnetic bilayers

The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the spin structure of the pinning layer with consecutive magnetization reversals of the pinned layer. Here we perform a detailed investigation of the temperature dependence of the bias field and its training effect. Consecutively cycled hysteresis loops of the soft layer are measured at various temperatures. We also derive a theoretical description of the temperature dependence of the training effect which is in agreement with the experimental data.