Exchange bias inducing temperature*

Characteristic temperatures governing behavior of ferromagnetic - antiferromangetic (F-AF) heterostructures are discussed. The inducing temperature, $T_{ind}$, at which the easy direction of magnetization is established, is in general case different from the maximum temperature at which exchange bias may exist $T_B$ (blocking temperature) and the N\'eel temperature of the antiferromagnet $T_N$. The case of $T_{ind} < T_N$ suggests presence of a frustrated interfacial AF spin structure in the system, otherwise $T_{ind} = T_N$. If $T_B = T_{ind} < T_N$, the interfacial F-AF interactions are stronger than that between the interfacial AF spins and the rest of the AF part, assuming rotation of those spins during the magnetization reversal. The exchange bias value in this case is determined by the latter AF exchange coupling. In the case of $T_B < T_{ind} < T_N$, the interfacial AF spins stay stable, and the exchange bias field is determined by the interfacial F-AF coupling.