Nanoscale diffusion at the interfaces in multilayers plays a vital role in controlling their physical properties for a variety of applications. In the present work depth-dependent interdiffusion in a Si/Fe/Si trilayer has been studied with subnanometer depth resolution using x-ray standing waves. High depth selectivity of the present technique allows one to measure diffusion at the two interfaces of Fe, namely, Fe on Si and Si on Fe independently, yielding an intriguing result that Fe diffusivity at the two interfaces is not symmetric. While the values of activation energy at the two interfaces are comparable, the main difference is found in the pre-exponent factor suggesting different mechanisms of diffusion at the two interfaces. This apparently counterintuitive result has been understood in terms of an asymmetric structure of the interfaces as revealed by depth selective conversion electron M\"ossbauer spectroscopy. This asymmetry is in turn explained by peculiarities during Si/Fe/Si layer formation by sputter deposition, in particular due to the difference between the surface free energies of Fe and Si.

Atomic diffusion at nanometer length scale may differ significantly from bulk diffusion, and may sometimes even exhibit counterintuitive behavior. In the present work, taking Cu/Ni as a model system, a general phenomenon is reported which results in sharpening of interfaces upon thermal annealing, even in miscible systems. Anomalous x-ray reflectivity from a Cu/Ni multilayer has been used to study the evolution of interfaces with thermal annealing. Annealing at 423 K results in sharpening of interfaces by about 38%. This is the temperature at which no asymmetry exists in the interdiffusivities of Ni and Cu. Thus, the effect is very general in nature, and is different from the one reported in the literature, which requires a large asymmetry in the diffusivities of the two constituents [Erdélyi et al., Science 306, 1913 (2004)]. The general nature of the effect is conclusively demonstrated using isotopic multilayers of ${}^{57}\mathrm{Fe}/{}^{\mathrm{natural}}\mathrm{Fe}$, in which evolution of isotopic interfaces has been observed using nuclear resonance reflectivity. It is found that annealing at suitably low temperature (e.g., 523 K) results in the sharpening of the isotopic interfaces. Since chemically it is a single Fe layer, any effect associated with concentration dependent diffusivity can be ruled out. The results can be understood in terms of fast diffusion along short-circuit paths like triple junctions, which results in an effective sharpening of the interfaces at relatively low temperatures.

Copper nitride thin films deposited by the rf reactive sputtering technique at three different substrate temperatures are irradiated by 200 MeV Au¹⁵⁺ ions. The on-line fluence dependent elastic recoil detection analysis (ERDA) study shows loss (>400 atoms/ion) of nitrogen from the films. The depletion rate of N is quite high as compared to sputtering rate normally observed in the regime of elastic collisions. This is attributed to the electronically mediated energy loss (S_e) which in this case is dominant as compared to the energy loss due to nuclear collisions (S_n). The aspects based on the physical properties of the films (surface morphology and crystallinity) that play an important role in enhancing the coupling of the energy of incident ions to the lattice atoms, causing atomic ejection are discussed. Crystallinity and surface morphology of the films are studied by the grazing angle X-ray diffraction (GAXRD) and the atomic force microscopy (AFM) techniques.

A detailed study on the microstructural evolution of the ${\mathrm{Fe}}_{73.9}{\mathrm{Cu}}_{0.9}{\mathrm{Nb}}_{3.1}{\mathrm{Si}}_{13.2}{\mathrm{B}}_{8.9}$ (Finemet) alloy upon Joule heating and its correlation with the magnetic properties is reported. Mössbauer spectroscopy suggests the coexistence of soft nonstoichiometric ${\mathrm{Fe}}_3\mathrm{Si}$ and hard iron boride magnetic phases. The uncoupled magnetic character of these phases is evidenced by dc-hysteresis loop measurements. X-ray diffraction results display an excellent agreement with the magnetic characterization. The magnetic contribution of the soft phase has been decreased from 70% to 10% with increasing annealing current and time. The switching field value for the soft magnetic phase is $50\mathrm{A}∕\mathrm{m}$ , which is very less as compared to $2000\mathrm{A}∕\mathrm{m}$ , for the hard magnetic phase. Existence of uncoupled soft and hard magnetic phases makes these systems suitable for use as magnetic labels.