Magnetic and magnetotransport properties of (100)Fe/Pd superlattices (abstract)

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It has recently been reported that Fe layers can couple through Pd interlayers, with at least one region of weak antiferromagnetic coupling.¹ This system, with coupling fields of only a few tens of Gauss, is potentially attractive for low-field device applications. Additionally, compared to the case of multilayer systems based on noble metal spacer layers, the high paramagnetic susceptibility of Pd and its tendency to ferromagnetic order are expected to lead to modified coupling mechanisms. We report on the growth, structural properties, magnetic properties, and magnetotransport properties of epitaxial (100)Fe/Pd superlattices. Samples consisting of 10 bilayers, with Fe layer thicknesses 20 Å and Pd layer thicknesses in the range 10–50 Å (including in ``wedge'' geometries), have been fabricated by molecular beam epitaxy onto (100)MgO substrates. The structure was characterized by reflection high-energy electron diffraction, x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The structural and magnetic properties of the multilayers are found to be highly dependent on the growth procedures. Optimized growth conditions, including in particular the absence of any buffer layers, result in overall coercive fields below 15 G and allow the detection of small coupling fields. Magnetization measurements unambiguously reveal the presence of a weak uniaxial anisotropy in the Fe layers, resulting in split hysteresis loops along one of the two in-plane 100Fe directions. These loops are similar to those normally associated with antiferromagnetic (AFM) coupling. No evidence of AFM coupling has been found in the present study. Magnetoresistance measurements show abrupt changes of resistivity of up to 1.5% at low temperatures, which can be well explained by anisotropy effects during rapid reversals of the Fe layers. Journal of Applied Physics is copyrighted by The American Institute of Physics.