Growth, thermal stability and oxidation of Ag/Fe and Ni/Fe bilayers

A study of the growth, thermal stability and oxidation of Ag/Fe and Ni/Fe on MgO(1 0 0) is presented. The layers were found to grow epitaxially. The Ag layer grows as an (0 0 1) single crystal layer on the epitaxial Fe(0 0 1) layer. The Ni layer grows as a (0 1 1) layer with a line structure of domains. Upon annealing of the Ag/Fe bilayers at 200 degreesC and 320 degreesC, round holes were formed in the top layer of Ag. After exposure to O-2 at pressures of 0.1-30 mbar and at 200 degreesC and 320 degreesC a rough layer of Fe-oxide is formed on top of the still epitaxial Ag layer. The speed of oxidation is not impeded by the Ag cap layer. A model to explain these observations is presented. The thermal stability and the resistance against oxidation of the Ni/Fe bilayers was found to be much better. Some Ni/Fe interdiffusion was observed after annealing in vacuum for 30 h. After oxidation in 10 (- 6) mbar O-2 at 200 degreesC for 40 h and subsequent air exposure only a thin Fe-hydroxide layer was observed. The results obtained can be of interest to judge the stability of magnetic multilayers. (C) 2001 Elsevier Science B.V. All rights reserved.