E. N. Sheftel

Atomic Force Microscopy Measurements of Magnetostriction of Soft-Magnetic Films

A method for direct measuring the magnetostriction of ferromagnetic films (deposited on nonmagnetic substrates) in using an atomic force microscope was suggested. In measuring the magnetostriction for films 10 [mm] in length and 0,2 [μm] in thickness, which were deposited on substrates 200 [μm] thick, the minimum measured magnetostriction magnitude is ~10-7. The procedure was tested for Ni and Fe films. The magnetostriction magnitudes measured for the films are comparable with those obtained by other magnetostriction-measuring methods. The effect of alloying with zirconium and nitrogen on the magnetostriction of nanocrystalline Fe films was studied.

Magnetic anisotropy induced in the nanocrystalline FeZrN films prepared by oblique-angle magnetron sputtering

Nanocrystalline Fe77Zr7N16 films are prepared by oblique-angle magnetron sputtering. The effect of the ion beam angle and subsequent annealing on the phase and structural states, the coercive force, the saturation magnetization, the remanent magnetization, and the induced in-plane magnetic anisotropy field has been studied. The possibility of natural ferromagnetic resonance in these films at gigahertz frequencies is estimated.

Micromagnetic structure of soft magnetic nanocrystalline Fe-based films

Results of a quantitative determination of parameters of the micromagnetic structure of nanocrystalline Fe, Fe95Zr5, Fe90N10, and Fe85Zr5N10 films prepared by magnetron sputtering have been reported. The magnetocrystalline (K1), magnetoelastic (KME), magnetostatic (KMS), and surface (Ka,s) anisotropy constants have been shown to be components of the effective local anisotropy (Keff) constant determined experimentally. The shape of hysteresis loops is determined by the existence of two main components of macroscopic effective magnetic anisotropy, one of which is caused by local (within a nanograin) magnetic anisotropy averaged over the exchange interaction length, while the other is related to magnetoelastic anisotropy due to residual macrostresses.

Electron microscopy of phase and structural transformations in soft magnetic nanocrystalline Fe-Zr-N films

The effect of deposition conditions (film thickness) on the structure of soft magnetic Fe80–78Zr10N10–12 films formed by reactive magnetron deposition on a heat-resistant glass substrate has been investigated by analytical transmission electron microscopy, high-resolution electron microscopy, and diffraction analysis. The processes of evolution of the phase and structural state of films and the film-substrate interface upon annealing in the temperature range of 200–650°C have been analyzed taking into account the thermodynamic, kinetic, and structural factors and the specific features of the nanocrystalline state.

Evolution of the phase-structure state during annealing of Fe-ZrN films grown by magnetron sputtering

The evolution of the phase-structure state of Fe-ZrN films grown by RF magnetron sputtering and annealed at T = 200–650°C has been studied by transmission electron microscopy, high-resolution electron microscopy, and X-ray diffraction analysis. It has been found that the initial state of the film contains 1- to 5-nm crystallites of α-Fe-based solid solution supersaturated with nitrogen. The number of such crystallites increases, the concentration of nitrogen in them decreases and 2- to 10-nm nanocrystallites of ZrN and Fe2N nitride phases appear after annealing. The formation of zirconium nitride at the first stage (200–500°C) is associated with a decrease in the degree of supersaturation of the α-Fe lattice with nitrogen. At a higher annealing temperature (650°C), a decrease in the nitrogen concentration in the lattices of both the bcc Fe and zirconium nitride phase leads to the formation of iron nitride crystallites.

Effects of annealing on the magnetic properties and microstructure of Fe-ZrN nanocomposite films

We have studied the influence of thermal annealing on the magnetic properties and microstructure of 0.7-μm-thick Fe-ZrN nanocomposite films obtained by a reactive RF magnetron sputtering technique on non-conductive substrates. The near-surface and bulk magnetostatic characteristics of the films were studied using magnetooptical and vibrating-sample magnetometers, respectively. The microstructure was determined by X-ray diffraction. It was established that the magnetic characteristics strongly depend on the annealing temperature. These dependences are explained by structural changes induced in the films by the thermal treatment.

Role of C: Zr stoichiometry in the formation of a nanocrystalline structure and magnetic properties in Fe87-x Zr13Cx films

X-ray diffraction analysis was used to study the structure of as-sputtered and annealed Fe-13 at. % Zr-C films, which were produced by reactive magnetron sputtering and characterized by stoichiometric and nonstoichiometric (with respect to ZrC) at. % C to at. % Zr ratios. A special packet of programs was used to resolve wide reflections observed in X-ray diffraction patterns of the films. The as-sputtered films of all compositions were found to be amorphous in terms of X-ray diffraction. The thermal stability of the amorphous phase increases as the C: Zr ratio in the films departs from the stoichiometric ratio (1: 1) characteristic of the monocarbide ZrC. Annealing leads to the formation of a mixed (amorphous + nanocrystalline) structure. Depending on the carbon content and annealing temperature, the phase composition of the films is represented by different combinations of phases, such as bcc α-Fe (the basis phase), fcc ZrC, monoclinic Fe2C, monoclinic Fe2.5C, orthorhombic Fe3C, and Fe23Zr6. After annealing at 550°C, the best magnetic properties are characteristic of the films having the stoichiometric composition with respect to ZrC (at. % C: at. % Zr ∼ 1).

X-Ray diffraction study of the evolution of phase and structural state and macroscopic stress during annealing of soft magnetic Fe95 − xZr5Nx films prepared by ion-plasma deposition

The evolution of the phase composition, nanostructure parameters, and macroscopic stress in soft magnetic Fe95 − xZr5Nx films (prepared by ion-plasma deposition onto quartz substrates) during their annealing has been investigated by X-ray diffraction. During deposition, depending on the N content, either a mixed structure composed of an X-ray amorphous phase enriched in Zr and N and a crystalline phase (α-Fe(N) solid solution) or an X-ray amorphous phase enriched in Fe, Zr, and N is formed in the films. During annealing, depending on the temperature and nitrogen content, different combinations of crystalline phases (α-Fe(N) and Zr(N) solid solutions, α-Fe, Fe4N, Fe2N, ZrO2) are formed in the films. The large compressive stress formed in the films during deposition changes to a lower tensile stress during annealing.

Magnetization Correlations and Random Magnetic Anisotropy in Nanocrystalline Films Fe78Zr10N12

The quantitative analysis of static ferromagnetic correlations in nanocrystalline films Fe78Zr10N12 was performed by two methods: the correlation magnetometry technique and magnetic force microscopy. The data, obtained by both methods, prove to be in good agreement.

Investigation of the magnetic properties and magnetic structure parameters of nanocrystalline Fe79Zr10N11 films

The magnetic properties (magnetization curve, ferromagnetic resonance spectrum) of nanocrystalline Fe79Zr10N11 films obtained by RF magnetron sputtering with subsequent annealing were studied experimentally, along with the fundamental magnetic constants of these films (saturation magnetization MS, local magnetic anisotropy energy K, and the exchange coupling constant A). The magnetic properties are discussed within the random magnetic model, which determines the correlation of the magnetic properties with the fundamental magnetic constants and nanostructure parameters (grain size, magnetic anisotropy, and correlation radius RC). The exchange correlation length 2RL for the film magnetic microstructure was determined by correlation magnetometry.