Training effect of the exchange bias in Co/CoO bilayers originates from the irreversible thermoremanent magnetization of the magnetically diluted antiferromagnet

The irreversible thermoremanent magnetization (m super(irr) sub(TRM)) of a sole, magnetically diluted epitaxial antiferromagnetic Co sub(1-y)O(100) layer is determined by the mean of its thermoremanent magnetizations (m sub(TRM)) at positive and negative remanence. During hysteresis-loop field cycling, m super(irr) sub(TRM) exhibits successive reductions, consistent with the training effect (TE) of the exchange bias measured for the corresponding Co sub(1-y)O(100)/Co(1120) bilayer. The TE of exchange bias is shown to have its microscopic origin in the TE of m super(irr) sub(TRM) of the magnetically diluted antiferromagnet.