Effect of interface on exchange coupling in NiFe/FeMn system

The influence of the interface between NiFe and FeMn layers on the exchange coupling in the NiFe/FeMn system was investigated experimentally. The state of the interface between NiFe and FeMn thin films depends on the sequence of the NiFe and FeMn layers, deposition conditions and underlayer. The exchange coupling was exhibited only for samples with the FeMn film crystallized into the γ-phase. The value of an exchange bias field barely depends on the amount of the γ-FeMn phase. Even a small amount of the γ-FeMn phase localized at the interface can provide a strong enough exchange coupling in the NiFe/FeMn system. The samples deposited on the Ta underlayer at room temperature exhibited the lowest roughness, smallest crystallite size and highest exchange coupling. At these conditions the interface between the NiFe and FeMn layers is smooth and sharp and results in a homogeneous and strong enough exchange bias field and low coercivity. The annealing changes the exchange coupling in the NiFe/FeMn system due to modification of the interface between the layers