Influence of He-ion irradiation on thin NiMn/FeNi exchange bias films.

Using synchrotron x-ray diffraction and reflectivity, we studied the transition from the paramagnetic NiMn phase to the chemically ordered, antiferromagnetic L1₀ phase of NiMn/Fe₁₉Ni₈₁ thin films deposited on a Si/SiO₂ substrate as a function of the annealing temperature. The transformation to a dominating L1₀-ordered NiMn film takes place between 300 and 400 °C irrespective of the irradiation. This is also consistent with magnetization reversal measurements of the corresponding permalloy layers. The benefit of the ion irradiation is a reduction of the mosaicity for both the NiMn and the permalloy film, and a smoothening of internal interfaces. [ABSTRACT FROM AUTHOR]