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The crystal structure, microstructure, and magnetic properties for a series of Cu/FePt bilayer films were investigated. The samples were prepared by depositing a Cu top layer on a highly ordered L10 FePt film. To promote interdiffusion, the bilayer samples were annealed at a temperature Td ranging from 300 to 800 °C. X-ray diffraction data indicate that observable diffusion occurs at 400 °C. The maximum coercivity thus obtained is 14.0 kOe, which is 24% larger than that of the ordered FePt film without a Cu top layer. The high Hc can be attributed to the diffusion of copper atoms through the grain boundaries of the magnetic films, which may produce extra pinning sites for domain-wall movement. The ΔM data measured from the Henkel plots of annealed Cu/FePt films change from negative to positive values as Td is raised from 400 to 800 °C. This can result from the effects of demagnetization coupling and exchange coupling and is further explained from the variation of squareness ratios of hysteresis loops. [ABSTRACT FROM AUTHOR]

The Fe[sub 53]Pt[sub 47] thin films with varying thickness were prepared using dc magnetron sputtering at various substrate temperatures (i.e., from 250 to 600 °C) on to CrMo seeded glass substrates. The powder x-ray diffraction studies reveal that the ordered fct γ[sub 2]-FePt phase begins to appear starting from the substrate temperature of 250 °C. The estimated ordering parameters show that the films prepared at 300 °C are well ordered and ordering parameters increase slowly as increasing substrate temperatures. On nitridation of the Fe[sub 53]Pt[sub 47] thin films, expansion of the face centered tetragonal crystal lattice along the c axis is observed. The saturation magnetization is decreased with decreasing film thickness. This has been explained mainly on the basis of size and surface effects of nanocrystals in the films including intergranular interactions. Maximum coercivity of 8.7 kOe is observed for the film thickness of 350 nm. The drastic decrease in magnetization with the increase in nitridation time duration has been attributed to the spin pairing effects as a result of electron supply from interstitial nitrogen atoms to the 3d bands of iron atoms. We observed an increase of H[sub c] from 7.8 kOe for non-nitrided Fe[sub 53]Pt[sub 47] film to 10.8 kOe for a 3 h nitrided film. [ABSTRACT FROM AUTHOR]

The influences of an Ag buffer layer on the magnetic properties of ultrathin Co/Ge(111) films grown at ambient temperature were studied using the surface magneto-optic Kerr effect technique. Due to the intermixing of Co adatoms and Ge(111) substrate, a nonferromagnetic layer forms at the initial stage of the deposition for Co/Ge(111) films. We demonstrate experimentally that the ferromagnetic inactive layer can be reduced by introducing an Ag buffer layer and the orientation of the easy axis of magnetization remains unchanged. Three magnetic phases have been resolved for Co/Ag/Ge(111) films with a Ag thickness less than 6 monolayers. In the phase diagram, the boundary between ferromagnetic and nonmagnetic regions shifts to a lower Co thickness from 10 to 5 monolayers as the thickness of the Ag layer increases from 0 to 6 monolayers. [ABSTRACT FROM AUTHOR]

Phase change memory has been considered as one of the most promising alternatives for next-generation nonvolatile semiconductor memory. Modification of phase change materials by impurity doping has been proved to be an effective way to improve phase change memory device performance. In this study, the most common phase change material, Ge2Sb2Te5 (GST), was employed, and its intrinsic properties were modified using boron-ion implantation. The GST films were implanted with 20 keV boron ions to fluences of 5 × 1014 and 5 × 1015 ions/cm2. The characteristics of the virgin and boron-implanted GST films were investigated by SIMS, XRD, and in situ resistance measurement. The kinetics of the thermally activated phase transition was also analyzed on the basis of the Arrhenius relationship. The results revealed that both crystallization temperature and activation energy of crystallization increase with increasing the boron fluence. The data retention capability is also enhanced from 83 to 88 °C, corresponding to a criterion of 10-year archival lifetime. In addition, the XRD spectra indicated that high-fluence boron-ion implantation partially inhibits the transition of the GST films from face-centered cubic phase to hexagonal close-packed phase. In conclusion, the thermal stability of the GST films can be improved through boron-ion implantation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Roles of rapid thermal annealing (RTA) on the evolution of crystallographic anisotropy of single-layered FePt films have been characterized. We observed a huge biaxial tensile stress of 2.18 GPa induced with increasing heating rate from 0.5 to 40 K/s. The result is a transition of orientation from (111) to perfect (001) texture. The later then degrades at heating rates ≥80 K/s due to morphological variation. The advantages of RTA are to induce tensile stress by densification reaction within a very short time and to simultaneously impede thickness-dependent dynamic stress relaxation. [ABSTRACT FROM AUTHOR]

The use of an ultrathin Ru-Ta--C film as a barrier for copper metallization in sub-32-nm ultra-large-scale integration (ULSI) has been evaluated. The films, fixed at 5 nm, were deposited by magnetron sputtering using Ru and TaC targets, and the film composition and structure were adjusted by tuning the respective deposition power. The structure of the au-Ta-C films gradually changed from Ru4Ta(C) to nanocrystalline or nearly amorphous when optimizing TaC. For a sandwiched scheme of Cu/Ru82Ta12C5/Si or Cu/Ru77Ta15C7/Si, the failure temperature was at least 750°C. We also electroplated Cu directly onto a Ru-Ta-C film without Cu seeding. Because of their low resistivity ( < 100 μ: cm) and high thermal stability, Ru-Ta-C films are promising as a Cu barrier. [ABSTRACT FROM AUTHOR]

Fe100-xPtx (x = 20, 25, and 30) thin films with nominal thickness 50 nm were prepared by radio-frequency (RF) magnetron sputtering onto glass substrates. Crystallographic structure and magnetic properties of such films were investigated by varying Fe content, annealing temperature (400-700 °C), and heating process. Crystallographic structure obtained by X-ray diffraction (XRD) indicated that ordering of L12Fe3Pt phase takes place for Fe75Pt25 postannealed above 400 °C. Ordering parameter of the Fe75Pt25 sample increases from 0.29 to 0.94 as annealing temperature rises from 400 °C to 700 °C. Saturation magnetization 1270 emu/cm³ was obtained in Fe75Pt25 films annealed at 700 °C. Fe70Pt30 films annealed at 700 °C show similar characteristics with those of Fe75Pt25, while Fe80Pt20 films exhibit paramagnetism due to disordered Fe-rich face-centered cubic (fcc) structure. Postannealing seems necessary for formation of pure L12Fe3 Pt phase while in situ annealing leads to formation of a metastable tetragonal Fe3 Pt phase, as confirmed by XRD. [ABSTRACT FROM AUTHOR]

High-quality epitaxial ZnCo0.07O films deposited at room temperature were obtained by using reactive ion beam sputtering. Room- temperature ferromagnetic behavior of ZnCoO was observed with a coercivity of 70 Oe. We observed the loop shift at 5 K in the field-cooled samples of ZnCoO/Cu/IrMn and an enhanced coercivity in the zero-field-cooled samples, which indicated the existence of exchange coupling between ZnCoO and IrMn through a thin Cu layer (0.15 nm). Furthermore, the exchange field of ZnCoO was increased from 55 to 113 Oe by increasing the cooling field from 3 to 15 kOe. [ABSTRACT FROM AUTHOR]