Origin of training effect of exchange bias in Co/CoO due to irreversible   thermoremanent magnetization of the magnetically diluted antiferromagnet
  The irreversible thermoremanent magnetization of a sole, magnetically diluted epitaxial antiferromagnetic Co$_{1-y}$O(100) layer is determined by the mean of its thermoremanent magnetizations at positive and negative remanence. During hysteresis-loop field cycling, thermoremanent magnetization exhibits successive reductions, consistent with the training effect (TE) of the exchange bias measured for the corresponding Co$_{1-y}$O(100)/Co bilayer. The TE of exchange bias is shown to have its microscopic origin in the TE of the irreversible thermoremanent magnetization of the magnetically diluted AFM. 
S. R. Ali, M. R. Ghadimi, M. Fecioru-Morariu, B. Beschoten, and G.   G\"untherodt
cond-mat.mtrl-sci