The effect of the exchange coupling strength J between NiFe and FeMn layers on the magnetization process in NiFe/FeMn structures was investigated. Samples with structures of NiFe/impurity (or Cu)/FeMn and NiFe/FeMn were prepared and measured to determine their hysteresis loop shift Hp and coercivity Hc. It is often assumed that Hp is proportional to J. However, our results show that Hp dependence on J is not monotonic. A phenomenological model is proposed to explain the results. A better method for estimation of J is also proposed.