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Layered magnetic structures composed by alternating ferromagnetic (FM) and antiferromagnetic (AFM) thin films play a fundamental role in the development of new generation spintronic devices. When transition metals oxides like NiO and CoO are employed as AFM materials, indirect interaction between the FM layers due to conduction electrons is excluded, thus a large contribution from direct exchange coupling across the AFM and the interfaces is expected. We have been able to epitaxially grow good quality NiO and CoO thin films onto Fe(001) substrates by reactive deposition, and embed them in FM/AFM/FM trilayers with Fe as FM material. Recently, we have characterized such systems with NiO as AFM material, evidencing different magnetic behaviors as a function of the NiO thickness. These included an evolution of the AFM anisotropy [1] and different alignments between the Fe layers magnetizations [2,3]. Now we focus on similar multilayers with CoO as AFM material. Comparison of previous studies on NiO/Fe layered magnetic structures with a different choice of the transition metal oxide could shed more light on the role of the interface properties on the magnetic behavior of such systems. Moreover, the lower Nèel temperature and the higher magnetocrystalline anisotropy of CoO with respect to NiO, allowed to perform a field cooling and to obtain exchange bias, which had been hindered in the NiO case due to dramatic oxidation/reduction processes at the interfaces. Here we present a chemical, electronic and magnetic investigation of Fe/CoO/Fe(001) trilayers, for different values of the CoO and Fe top layer thicknesses, by means of photoemission, spin-polarized inverse photoemission and magneto-optical Kerr effect. A thickness dependent magnetic coupling has been observed between the Fe layers. We also report on important chemical interactions occurring at the buried interfaces, that influence the magnetic coupling. The latter shows indeed intriguing differences with respect to the Fe/NiO/Fe(001) case.
[1] M. Finazzi, A. Brambilla, P. Biagioni, et al., Phys. Rev. Lett. 97, 097202 (2006).
[2] A. Brambilla, P. Biagioni, M. Portalupi, et al., Phys. Rev. B 72, 174402 (2005).
[3] A. Brambilla, P. Biagioni, N. Rougemaille, et al., Thin Solid Films 515, 712 (2006).
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