Initial stages of oxidation of the Ni3Al alloy: structure and composition of the aluminum oxide overlayer studied by XPS, LEIS and LEED

Magnetic anisotropy of Fe and Co adatoms and Fe clusters magnetically decoupled fromNi3Al(111)by an alumina bilayer

“…Comparison of the magnetization curves acquired at the Fe and Ni edges demonstrates a distinctly different switching behavior for the transition-metal nanostructures and the substrate excluding strong dipolar or exchange coupling. Altogether, these findings demonstrate that the alumina film, despite its thickness of only two atomic layers, [7][8][9] gives rise to an effective decoupling of the magnetic atoms from the conduction electrons of the underlying metal, as expected by the large band gap of 7-8 eV observed for the present system. 10 Our data reveal an out-of-plane easy magnetization axis for Fe and Co.…”

“…This model was confirmed by x-ray photoelectron spectroscopy finding up to 100% Ni in the atomic layers close to the interface with the oxide. 8 The probing depth of x-ray absorption spectroscopy in the TEY mode is limited to a few nanometers implying that most of the Ni signal is originating from the Ni-rich layers near the oxide-metal interface in which the Ni atoms probably have a magnetic moment close to the Ni bulk value. This assumption is corroborated by the finding of a strongly increasing magnetic moment with increasing Ni content in bulk nickel aluminum alloys.…”

Models for heterogeneous catalysts: studies at the atomic level

“…It has been shown that even films with a thickness of just a few Angstroms can exhibit physical properties characteristic of the bulk material (Freund 1995). The traditional method to prepare such films is the oxidation of the native metal (Freund 1995) or an alloy (Jaeger et al 1991;Libuda et al 1994;Bardi et al 1992;Becker et al 1998), although this often results in amorphous or polycrystalline overlayers [e.g., Al oxide on Al (Chen et al 1987;Belton and Schmieg 1988a, b;Chen et al 1992), or Si oxide on Si (Rochet et al 1986;Pantelides et al 1978)] or films with a rather high defect density. This is due to the large mismatch which usually exists between the metal and the oxide lattice [e.g., NiO(100)/Ni(100) (Bäumer et al 1991)].…”

“…This is due to the large mismatch which usually exists between the metal and the oxide lattice [e.g., NiO(100)/Ni(100) (Bäumer et al 1991)]. There are a few examples where well-ordered crystalline films can be obtained in this way [e.g., Cr 2 O 3 (111) on Cr(110) (Kuhlenbeck et al 1992;Rohr et al 1997a, b) or Al 2 O 3 on NiAl(110) (Jaeger et al 1991;Libuda et al 1994) and Ni 3 Al(111) (Bardi et al 1992;Becker et al 1998)].…”

Effect of the Noble Metals Addition on the Oxidation Behavior of Ni3Al

“…erefore, it is desirable for the growth of an α-Al 2 O 3 layer [1,14]. It has been observed that the only growth of an outer scale of Al 2 O 3 is possible under the following conditions, by increasing both the temperature and concentration of Al [12], where the oxidation process is carried out at oxygen partial pressures below the equilibrium of NiO formation [13,[19][20][21] and also in alloys which were implanted with B + and Cr + ions [14]. Increasing the oxygen partial pressure and temperature, it is possible to form the spinel NiAl 2 O 4 at the NiO/Al 2 O 3 interface [22].…”