Exchange-biased NiFe/FeMn/Co trilayers were grown by dc magnetron sputtering and analyzed by in-plane ferromagnetic resonance using Q-band microwaves. The experiments revealed that distinct Co and NiFe resonance modes were excited by the microwave field. A misalignment between the anisotropy axes of the magnetic layers was deduced from the angular variations of the resonance fields, which also showed the effects of uniaxial and unidirectional anisotropies. A phenomenological model was used to fit the experimental results taking also into account a rotatable anisotropy field associated to the domain structure of the FeMn layer and the magnetic history of the films.

No abstract

The magnetic interactions in the Ir 20 Mn 80 / Co/ Ru/ Py ͑Py= Ni 81 Fe 19 ͒ spin valve structures have been studied by magnetization measurements. The Ru thickness was varied between 24 and 58 Å, and the thicknesses of the other layers were keep constant, resulting in multilayers with a strong exchange bias field ͑H eb ͒ and weak oscillatory interlayer coupling. The bilinear and biquadratic coupling constants between Co and Py and the exchange anisotropy at the IrMn/Co interface were considered for modeling the magnetic hysteresis loops of the whole system. The interplay between these interactions gives rise to an increase ͑decrease͒ in the H eb value of the Co pinned layer for antiferromagnetic ͑ferromagnetic͒ interlayer coupling, if compared to the system with no interlayer coupling, and in a small exchange anisotropy field, proportional to the bilinear coupling energy, induced to the Py free layer.

No abstract

The IrMn/Co/NM/Ni81Fe19 spin valves, with the nonmagnetic (NM) spacers of Ru and Cu, were grown by sputtering and analyzed by magnetization versus magnetic field measurements at several temperatures. The loop of the free layer exhibits a loop shift proportional to the interlayer coupling strength. For fitting the NM layer thickness dependence of this loop shift, the oscillatory interlayer and the magnetostatic Néel mechanisms were considered. These analyses provided quantitative values of both contributions and showed that the oscillatory coupling mechanism dominates in the system with Ru spacer, while the Néel coupling mechanism dominates for the Cu spacer. In both systems, the temperature variations of the coupling are attributed to the spacer and spacer/magnet interfaces.