Epitaxial growth and characterization of CoO/Fe(001) thin film layered structures

Self-organized nano-structuring of CoO islands on Fe(001)

“…2b) shows the Co 2p energy region. Here, the first significant information is the line shape of the 6.4 ML thick CoO layer (top spectrum), which agrees very well with that expected for a CoO film [28,43,47,48]. Such a line shape did not change at higher thicknesses (not shown).…”

“…Also, no further traces of a metallic Fe signal can be seen, after the A c c e p t e d M a n u s c r i p t shoulder visible in the Co/Fe substrate spectra is attenuated by the growing CoO film. These observations indicate that the CoO film grows onto the Co/Fe substrate without inducing significant Fe segregation (and subsequent oxidation), at variance with the case of reactive deposition of CoO directly onto the Fe(001)-p(1 × 1)O surface [28]. This result is quite surprising, since the standard enthalpy of formation of CoO is higher (∆ f H 0 = -238 kJ/ mol O) than that of Fe oxides (∆ f H 0 = -272 kJ/ mol O for FeO, which has the higher value), resulting in a lower oxygen affinity for Co than for Fe [44].…”

“…Furthermore, CoO films coupled to ferromagnetic substrates (like Fe), show the well-known and technologically important exchange bias effect [25,26], which makes this kind of systems even more appealing. Previous investigations on CoO/Fe(001) layered structures reported on complicated and extended chemical reactions at the interface, which is common when transition metal oxides are grown on the reactive Fe substrate [18,[27][28][29]. Scanning Tunneling Microscopy (STM) measurements observed a three-dimensional growth of CoO without any particular order [30].…”

Exchange bias in epitaxial CoO/Fe bilayer grown on MgO(001)

“…[9] In contrast to numerous structural and magnetic studies of Co/CoO films, only a few articles concerning comparable Fe/CoO and CoO/Fe systems, in particular on MgO(001), can be found. [5,10 -14] Recent experiments have revealed that growing a chemically sharp CoO-Fe interface is a very challenging task [13,14] due to the rich Co-O phase diagram exhibiting several oxide phases and to the affinity of Fe for oxidation. To the best of our knowledge, there are no data relating the interfacial structure and magnetic properties of CoO/Fe/MgO(100).…”

Magnetic anisotropy at the buried CoO/Fe interface

“…20 Very recently, we have demonstrated that it is possible to prepare a CoO/Fe(001) interface characterized by the absence of any Fe oxide, 21,22 which is a quite unique feature with respect to the common experimental situations. 10,19,23 This result has been accomplished by exploiting an ultra-thin Co buffer layer with a bct cubic structure. 21,24 In that case, the CoO films were also a) Currently at Institute of Applied Physics, TU Wien, Vienna, Austria b) Electronic mail: alberto.brambilla@polimi.it characterized by a well-ordered mesa mound morphology for CoO thicknesses above a few monolayers (ML), occurring on account of stress relaxation through the formation of a network of misfit dislocations.…”