Effect of Interfacial Ion Migration on Oxidation in Fe/MgO/Gd Nanoheterostructures

Interfacial migration is one of the key problems in nanoheterostructures based on transition metal—rare earth multilayers separated by an oxide barrier. We studied one of such structures, Fe (10 Å) and Gd (10 Å) layers separated by an ultrathin barrier MgO spacer of 2, 4, and 6 monolayers, using X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XRR), and ab initio calculations. Surprisingly, regardless of the relative position and thickness of the barrier oxide layer with respect to metal layers of different types, the predominant oxidation of gadolinium and only traces of iron oxidation were observed. The ab initio calculations clearly show the formation of Gd2O3 and GdO at the interface of MgO and Gd layers. In the Fe layer the calculations discover domain-like magnetic structures.