We have studied the faceting and defaceting phase transitions of Pd/ W͑111͒. In apparent agreement with results of recent theoretical simulation ͓C. Oleksy, Surf. Sci. 549, 246 ͑2004͔͒, we find the fastest way to create the largest facets is to anneal at a temperature right below the temperature that the defaceting transition occurs. On the other hand, while the paths of faceting transitions show normal retardation as the cooling rate is increased, the paths of defaceting transitions show negligible dependence on the heating rate even if increased by 64-fold. Another notable observation is a phase separation of the surface into defaceted and faceted regions after long annealing time while there is more than enough Pd remaining to induce faceting of the whole surface. This leads us to the proposal that instead of thermal disorder, the observed defaceting transition of the Pd/ W͑111͒ system is mainly driven by local loss of Pd, which is due to thermal desorption. Such desorption loss could be effectively replenished via surface diffusion at the vicinity of the Pd 3d islands. The observed independence of the defaceting transition path on the heating rate is rationalized as the consequence of a balance in between the loss and the supply of Pd, which can establish very quickly as the temperature rises.

The crystalline structure and the magnetic properties of Co x Ni 1−x /Cu 3 Au͑100͒ films were characterized as functions of thickness and alloy composition. No apparent alloy effect on the crystalline structure was observed with x up to 11%. As the film thickness increases above ϳ8 monolayers ͑ML͒, the films clearly exhibited a progressively more relaxed structure. Due to the strain relaxation, both the first and the second spinreorientation transitions ͑SRT͒ occurred within 20 ML. The thickness region with perpendicular magnetization was strongly reduced by increasing the Co concentration. For x Ͼ 10%, no SRT was observed. By combining both the alloy effect and the strain relaxation effect, the SRT boundaries in the phase diagram can be described in a phenomenological model on the basis of magnetoelastics.

The structural and magnetic properties of room-temperature ͑RT: 300 K͒-grown and low-temperature ͑LT: 100 K͒-grown Mn/ Cu 3 Au͑100͒ thin films were investigated. Mn films deposited at RT and LT demonstrate very different behaviors in the crystalline structure, morphology, and magnetism. RT-Mn films reveal apparent layer-by-layer growth for 0 -2 ML ͑monolayer͒ followed by reduced oscillations. Although the medium-energy electron diffraction ͑MEED͒ oscillation is reduced, the intensity of specular spot increases monotonically after 6 -7 ML, inferring the tendency of smooth morphology. The study of scanning tunneling microscopy also shows that even in 19 ML Mn/ Cu 3 Au͑100͒, the surface morphology is composed of large terraces with the size up to hundreds of nanometers. The LT-Mn films reveal apparent layer-by-layer growth for 0 -5 ML followed by the reduced oscillations, and then the MEED intensity remains at low intensity, inferring the rough surface. The RT-and LT-Mn films exhibit a thickness-dependent structural transition from a face-centered cubic to a face-centered tetragonal structure at different critical thicknesses, ϳ12-14 and ϳ8 ML, respectively. Significant exchange bias is observed in Fe/ RT-Mn bilayers. It increases monotonously with Mn thickness. The exchange bias coupling in Fe/ LT-Mn is much weaker than Fe/ RT-Mn and drastically varies with Mn film thickness. The presence of exchange bias in the Fe/ Mn bilayers also indicates the antiferromagnetism of ␥-phase Mn/ Cu 3 Au͑100͒.