Influence of Cu seed layer on the magnetization reversal in exchange-biased FeMn/FeCo systems

Magnetization hysteresis loops are measured on FeMn/FeCo bilayers. The existence of the exchange bias effect up to room temperature is guaranteed by the presence of copper as a seed layer. We demonstrate that the choice of the growth parameters for Cu allows the control of the magnetic response of the structure, tuning the coercivity and the exchange field. The switching field distribution suggests different magnetization reversal mechanisms during the ascending and descending branches of the hysteresis loop. The evident noisy character of the data, during the reversal of the magnetization with respect to the initially set orientation, supports the picture of domain wall motion involving pinned states at magnetic defects, contrasting with the coherent magnetic moments rotation along the opposite branch.