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Thermodynamic studies are used for analyzing the mechanism of structural transition in nanocrystalline metals. The results have shown that relative to the crystallized nanocrystalline state, the face centered cubic (fcc) Fe has formed in the milled nanocrystalline state.

The microscopic structure of FePtCu ternary ordered alloys from both theoretical and experimental points of view is investigated. The findings from a comparison with the calculated density of states curve show that the Fe site of FePt ordered alloy replaced the Cu.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, α-Pt2Si, was successfully formed at the platinum/silicon oxide interface under 25-200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation. It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation. [ABSTRACT FROM AUTHOR]

The mechanism of structural transition in nanocrystalline metals was studied from a thermodynamic point of view. Crystal lattice distortion and interfacial effect were found to be the reasons for structural instability. Nanocrystalline Fe samples prepared by the milling method and by the crystallization method were used for analyses and comparison. The contributions of lattice distortion and interfacial energy to thermodynamics were calculated using the quasiharmonic Debye approximation and the Gibbs-Thomson equation, respectively. By examining the change in Gibbs free energy and considering the effect of negative stress of grain boundaries on the crystal volume change in structural transition, we calculated the critical grain size of fcc-Fe formation. Results show that relative to the crystallized nanocrystalline state, it is more likely that the fcc Fe forms in the milled nanocrystalline state. Whether or not the phase transition occurs in nanocrystalline materials is closely related to the preparation technology, the grain-boundary structure, and the grain size. [ABSTRACT FROM AUTHOR]

Specimens of Zr[sub 66.7]Cu[sub 33.3], Zr[sub 65.0]Al[sub 7.5]Cu[sub 27.5], and Zr[sub 65.0]Al[sub 7.5]Ni[sub 10.0]Cu[sub 17.5] amorphous alloys with different thermal stability were irradiated by high energy electrons at an accelerated voltage of 2000 and 1000 kV. Electron irradiation was performed at 298 and 103 K. Crystallization of three amorphous alloys was accelerated by this irradiation and nanocrystalline structures were obtained. The critical total dose required for crystallization of the amorphous phase by electron irradiation depends strongly on the irradiation temperature and stability of this amorphous phase. The phase stability and crystallization behavior of the amorphous phase are discussed based on the electron irradiation effect. [ABSTRACT FROM AUTHOR]

The magnetoresistance ratio (MR) and resistance area product (RA) of cap/NiFe/Al[O.sub.x] /CoFe stack with several cap layers are investigated and a model explaining correlation between MR ratio and RA and the cap layer material is proposed, in a viewpoint of the standard electrode potential. The highest MR ratio with nonmagnetic-NiFeZr cap is consistent with the lowest electrode potential of Zr, and it is believed that non-magnetic-NiFeZr cap realizes a steep NiFe/AlOx interface without the oxidation of NiFe.

A write-operating window with a 100% functional bit yield is obtained by the control of stray fields from synthetic antiferromagnetic (SAF) pinned layers in conventional magnetic random access memories. The symmetric switching astroid curves with no offset are obtained and the switching distributions are minimized at the zero offset field.