Fe-N Compounds Research Articles

Strength, plasticity, and spin transition of Fe-N compounds in planetary cores

Elastic and plastic properties of Fe-light element alloys and compounds are needed to determine the compositions and dynamics of planetary cores. Elastic strength and plastic deformation mechanisms and their relationship to electronic properties of ε-Fe7N3 and γ'-Fe4N mixture were investigated by x-ray diffraction and x-ray emission spectroscopy in the diamond anvil cell from 1 bar up to 60 GPa. X-ray diffraction shows that ε-Fe7N3 reaches a pressure of 15–20 GPa before undergoing bulk plasticity at a differential stress of 4.4–10.4 GPa. ε-Fe7N3 is stronger than γ'-Fe4N and hcp-Fe which achieve a flow stress of 1.5–3.6 GPa at 10–15 GPa and 2–3 GPa at ∼20 GPa, respectively. X-ray emission spectroscopy shows that a decrease in electronic spin moment begins before and completes after plastic flow onset for each nitride, suggesting that pressure-driven changes in electronic arrangement do not trigger a plastic response although they may modify the strength and plastic behavior of Fe-N compounds. Plastic deformation in ε-Fe7N3 and hcp-Fe results in a preferred orientation of (0001) normal to maximum compression, while γ'-Fe4N develops a maximum in the (110). These observations may be combined with measurements of elasticity to model seismic properties of cores of small planetary bodies such as Mars, Mercury, and the Moon.

Surface modification of a ferritic ductile iron through plasma nitriding

This text describes the plasma nitriding of a ductile iron, to increase the surface hardness and improve its wear behavior. A ferritic ductile iron was used and processed with gases (N2 + H2) for 5 hours in a treatment chamber built at the UNAM Physics Institute. The treated samples were characterized using scanning electron microscopy, atomic force microscopy, microhardness and X-ray diffraction. The presence of Fe-N compounds was corroborated on the surface of the material. Modifications in surface morphology and a 30% increase in microhardness were also obtained.

Density Functional Theory Approach to the Study of the Structural Stability of Nitrides of Iron and Nickel

Nitrides of transition metals such as iron and nickel are known to possess excellent properties relevant for technological applications. Among these, FeNhas been synthesized in zinc blende face centered cubic (F4 M) crystal structure while NiN has not been synthesized yet. Literature search revealed that hexagonal close packed and primitive tetragonal structures of these compounds have not been investigated to ascertain their preference.Therefore, the structural stability of Zinc blende face centered cubic, hexagonal closed packed and primitive tetragonal crystal structures of the compounds were investigated in this study. Generalized gradient approximation of Perdew-Burke-Ernzerhof revised for solids (GGA-PBEsol) as implemented in Quantum espresso package was used based on density functional theory for the computation. The results revealed that FeN and NiNcompounds prefer Zinc blende face centered cubic crystal structure as their equilibrium lattice parameters occurred at the least equilibrium minimum energies in this structure. The lattice parameters of FeN and NiN compounds in thezinc blende FCC crystal structure were computed to be 4.232 Å and 4.324 Å respectively in agreement with experiment and previous computations. The preference of zinc blende FCC crystal structure by these compounds imply they may possess highly directional covalent bonds that prefer a tetrahedral arrangement of atoms, thus forming good binary semiconductor compounds. Therefore, these compounds have high possibility of been synthesized in zinc blende FCC crystal structure.

Structural and Magnetic Properties of Nitrogen Acceptor Co-doped (Zn,Fe)Te Thin Films Grown in Zn-Rich Condition by Molecular Beam Epitaxy (MBE)

We have investigated the structural and magnetic properties of (Zn,Fe)Te:N thin films grown under Zn-rich condition with Fe composition fixed at 1.4% and N concentrations varying in the range [N] = 1.8 × 1018–5.1 × 1019 cm−3. Structural analysis by x-ray diffraction (XRD) detects some additional extrinsic diffraction peaks possibly from Fe-N compounds in the N-doped film with [N] = 5.1 × 1019 cm−3 only. Accordingly, x-ray absorption fine structure (XAFS) analysis reveals the shifting of Fe atoms from substitutional position for N-doped films with high N concentrations, [N] ≥ 1.8 × 1019 cm−3, whereas N-doped films with intermediate N concentrations [N] ≤ 4.3 × 1018 cm−3 are composed of pure diluted phase with substitutional Fe atoms in the valence state deviating from Fe2+. Magnetization measurement using SQUID confirms drastic change of magnetic properties; the linear dependence of magnetization on magnetic field, typical of van Vleck-type paramagnetism in the film without N-doping changes into room temperature ferromagnetic behaviors with hysteretic magnetization curves for N-doped films. The observed weak room temperature ferromagnetic behavior of the N-doped films with [N] ≤ 4.3 × 1018 cm−3 may reflect the deviation of substitutional Fe valence state from Fe2+ to Fe2+/3+ mixed states. On the other hand, the robust room temperature ferromagnetic behavior exhibited by N-doped films with [N] ≥ 1.8 × 1019 cm−3 may originate from precipitates of Fe-N compounds with Fe being in Fe2+/3+ or other valence state.

3D-ordered macroporous N-doped carbon encapsulating Fe-N alloy derived from a single-source metal-organic framework for superior oxygen reduction reaction

Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells. Fe-N compounds with excellent electrocatalytic oxygen reduction activity are considered to be one of the most promising non-precious metal materials for fuel cells, which focuses on the Fe-N4 single-atom catalysts and the iron nitride materials (such as Fe2N and Fe3N). A hybridized catalyst having a hierarchical porous structure with regular macropores could enable the desired mass transfer efficiency in the catalytic process. In this study, we have constructed a new type of hybrid catalyst having iron and iron-nitrogen alloy nanoparticles (Fe-N austenite, termed as Fe-NA) embedded in the three-dimensional ordered macroporous N-doped carbon (3DOM Fe/Fe-NA@NC) by direct pyrolysis of single-source dicyandiamide-based iron metal-organic frameworks. The as-synthesized composites preserve the hierarchical porous carbon framework with ordered macropores and high specific surface area, incorporating the uniformly dispersed iron/iron-nitrogen austenite nanoparticles. Thereby, the striking architectural configuration embedded with highly active catalytic species delivers a superior oxygen reduction activity with a half-wave potential of 0.88 V and a subsequent superior Zn-air battery performance with high open-circuit voltage and continuous stability as compared to those using a commercial 20% Pt/C catalyst.

The search for the new superconductors in the Ni-N system

Transition metal nitrides show a unique combination of superconducting and mechanical properties. In this study we perform a theoretical search of the intermediate compounds in Ni-N system, determine their superconducting transition temperatures (Tc ) and bulk moduli (K 0) in the wide range of pressures, from 0 to 300 GPa. We have revealed several nickel-rich interstitial compounds, Ni5N2, Ni3N, and Ni6N, and one nitrogen-rich compound, NiN2, as stable structures. At pressures above 100 GPa, previously unknown NiN with anti-nickeline structure is also stabilized. All found compounds are non-magnetic. The most promising for superconductivity NiN2 structure is stable against decomposition on the mixture of (Ni+N) from 3 to at least 300 GPa. The transition from marcasite-type NiN2-Pnnm to pyrite-type NiN2- occurs at 70 GPa. NiN2-Pnnm is an insulator with the band gap of about 1 eV, while NiN2- is a metallic phase. The calculated Tc of NiN2-Pnnm equals to 10−2 K, and the bulk modulus (K 0) equals to 225 GPa at 10 GPa, which is in excellent agreement with available experimental data. The comparison of Tc of compounds in the Ni-H and Ni-N systems with that of the Fe-H and Fe-N compounds, shows that hydrides and nitrides of nickel have lower Tc than hydrides and nitrides of iron, which is explained by the significant differences in crystal structures.

Effect of nitrogen acceptor co-doping on the structural and magnetic properties of (Zn, Fe) Te

We have investigated the effect of co-doping of nitrogen (N) acceptor impurity on the structural and magnetic properties of (Zn,Fe)Te. We grew (Zn,Fe)Te:N thin films by molecular beam epitaxy (MBE) with a fixed Fe composition 1.5% and varied N concentrations in the range of [N] = 8 × 1017– 4 × 1019 cm−3. Structural analyses by using x-ray absorption fine structure (XAFS) and transmission electron microscope (TEM) reveal that N-doped films with intermediate N concentration [N] = 8 × 1017– 7 × 1018 cm−3 are mainly composed of pure diluted phase with substitutional Fe atoms in the valence state deviated from Fe2+, while Fe is dominantly incorporated in an Fe-N compound at the highest N concentration [N] = 4 × 1019 cm−3. Accordingly, the magnetization measurement using SQUID confirms a drastic change of magnetic properties; a linear dependence of magnetization of magnetic field (M-H), typical of van-Vleck paramagnetism in the film without N-doping changes into ferromagnetic behaviors with a hysteretic M-H curves at the intermediate N concentrations and comes back to a linear M-H dependence at the highest N concentration. The ferromagnetism in the intermediate [N] range may reflect a deviation of the valence state of the substitutional Fe from Fe2+, while the linear M-H at the highest [N] would be attributed to precipitates of an Fe-N compound.

Performance analysis of Fe-N compounds based on valence electron structure

In this paper, the valence electron structure and the bond energy of covalent bonds of α-Fe and ε-Fe2N, ε-Fe3N and γ′-Fe4N were calculated by means of the empirical electron theory (EET). It was put forward that the valence electron structure parameter related to hardness is the covalent electron density, the valence electron structure parameters related to plasticity are the lattice electron density and the symmetry factor of the atomic bonding strength, the valence electron structure parameters related to corrosion resistance are the atomic total bonding energy and lattice electron density, and the valence electron structure parameter related to stability is the average atomic total bonding energy. The hardening and corrosion resistance mechanism of ion-based nitriding layer was discussed and the influence of three Fe-N compounds on the hardness, brittleness, corrosion resistance and stability were compared and analyzed from the perspective of electron structure. The calculation results show that the three Fe-N compounds, which have larger covalent electron density and average atomic total bonding energy and smaller lattice electron density than α-Fe, can improve the hardness and corrosion resistance of the iron-based surface. Among the three compounds, ε-Fe2N has the greatest hardness, corrosion resistance and stability, and the least brittleness. Therefore, during the nitriding process, efforts shall be made to prompt the formation of ε-Fe2N as much as possible.

Cultural characteristics Meyerozyma guilliermondii TY-89 on lard

We have investigated the effect of co-doping of nitrogen (N) acceptor impurity on the structural and magnetic properties of (Zn,Fe)Te. We grew (Zn,Fe)Te:N thin films by molecular beam epitaxy (MBE) with a fixed Fe composition 1.5% and varied N concentrations in the range of [N] = 8 × 1017– 4 × 1019 cm−3. Structural analyses by using x-ray absorption fine structure (XAFS) and transmission electron microscope (TEM) reveal that N-doped films with intermediate N concentration [N] = 8 × 1017– 7 × 1018 cm−3 are mainly composed of pure diluted phase with substitutional Fe atoms in the valence state deviated from Fe2+, while Fe is dominantly incorporated in an Fe-N compound at the highest N concentration [N] = 4 × 1019 cm−3. Accordingly, the magnetization measurement using SQUID confirms a drastic change of magnetic properties; a linear dependence of magnetization of magnetic field (M-H), typical of van-Vleck paramagnetism in the film without N-doping changes into ferromagnetic behaviors with a hysteretic M-H curves at the intermediate N concentrations and comes back to a linear M-H dependence at the highest N concentration. The ferromagnetism in the intermediate [N] range may reflect a deviation of the valence state of the substitutional Fe from Fe2+, while the linear M-H at the highest [N] would be attributed to precipitates of an Fe-N compound.

Study of the iron nitride FeN into the megabar regime

In this work, the nitrogen-rich portion of the Fe-N binary phase diagram is investigated up to 128 GPa. The samples, largely in excess of nitrogen, were laser-heated in diamond anvil cells to temperatures up to 2000 K at regular pressure intervals to help in crossing possible activation barriers towards the more stable phase. Three Fe-N compounds: ZnS-type FeN, Fe2N and NiAs-type FeN, are characterized by powder X-ray diffraction and their observed stability domain reported. Below 12.5 GPa, orthorhombic Fe2N is found to be the energetically-favored compound while NiAs-FeN becomes stable above 17.7 GPa. Energy-dispersive X-ray spectroscopy measurements and a Rietveld refinement confirmed the stoichiometry and structure of the recovered NiAs-FeN sample. A precise determination of its bulk modulus (K0 = 200(5) GPa) as well as its pressure derivative (K0′ = 5.3(2)) is obtained and, based on its unit cell axial ratio evolution, the NiAs-FeN compound appears to decrease in ionicity concomitantly with pressure. Within the pressure-temperature conditions reached here, the predicted iron pernitride FeN2 is not observed.

Pyrolysis-induced synthesis of iron and nitrogen-containing carbon nanolayers modified graphdiyne nanostructure as a promising core-shell electrocatalyst for oxygen reduction reaction

Low-cost facile fabrication of highly efficient non-precious-metal catalysts to replace commercial Pt-based catalysts for oxygen reduction reaction (ORR) has attracted great attentions, because it is significant for rapid commercialization of fuel cells. Based on a fact that graphdiyne, another member of the carbon family, has not been systematically investigated as a new carbon support to ORR catalysts. We here report an effective strategy for easy synthesis of a cheap iron-nitrogen-doped carbon nanolayers wrapped around graphdiyne core-shell electrocatalyst (Fe-PANI@GD-900) for ORR from one-step pyrolysis of iron and polyaniline loaded onto graphdiyne nanocomposite at 900 °C. Electrochemical results indicate that the catalyst exhibits unexpectedly high ORR activity with onset and half-wave potentials of 1.05 V and 0.82 V (vs. RHE), while its mass activity at given potentials is lower than that of the Pt/C catalyst. Moreover, Fe-PANI@GD-900 follows a direct four-electron reduction pathway, and its long-term stability is superior to Pt/C and other graphdiyne-based catalysts previously reported in the literature. The relatively excellent ORR performance may be largely attributed to the formation of high contents of graphitic-N and FeN compounds, and the addition of graphdiyne facilitating to absolutely accelerate ORR charge transfer and fully expose more N-doped active sites on the surface.

Dissimilar bacterial and fungal decomposer communities across rich to poor fen peatlands exhibit functional redundancy

Haynes, K. M., Preston, M. D., McLaughlin, J. W., Webster, K. and Basiliko, N. 2015. Dissimilar bacterial and fungal decomposer communities across rich to poor fen peatlands exhibit functional redundancy. Can. J. Soil Sci. 95: 219–230. Climatic and environmental changes can lead to shifts in the dominant vegetation communities present in northern peatland ecosystems, including from Sphagnum- to vascular-dominated systems. Such shifts in vegetation result in changes to the chemical quality of carbon substrates for soil microbial decomposers, with leaves and roots deposited in the peat surface and subsurface that potentially decompose faster. This study characterized the bacterial and fungal communities present along a nutrient gradient ranging from rich to poor fen peatlands and assessed the metabolic potential of these communities to mineralize a variety of organic matter substrates of varying chemical complexity using substrate-induced respiration (SIR) assays. Distinct microbial communities existed between rich, intermediate and poor fens, but SIR in each of the three sites exhibited the same pattern of carbon mineralization, providing support for the concept of functional redundancy, at least under standardized in vitro conditions. Preferential mineralization of simple organic substrates in the rich fen and complex compounds in the poor fen was not observed. Similarly, no preference was given to “native” organic matter extracts derived from each fen, with microbial communities opting for the most bioavailable substrate. This study suggests that soil bacteria and fungi might be able to respond relatively rapidly to shifts in vegetation communities and subsequent changes in the quality of carbon substrate additions to peatlands associated with environmental and climatic change.

Dissimilar bacterial and fungal decomposer communities across rich to poor fen peatlands exhibit functional redundancy

to the chemical quality of carbon substrates for soil microbial decomposers, with leaves and roots deposited in the peat surface and subsurface that potentially decompose faster. This study characterized the bacterial and fungal communities present along a nutrient gradient ranging from rich to poor fen peatlands and assessed the metabolic potential of these communities to mineralize a variety of organic matter substrates of varying chemical complexity using substrate-induced respiration (SIR) assays. Distinct microbial communities existed between rich, intermediate and poor fens, but SIR in each of the three sites exhibited the same pattern of carbon mineralization, providing support for the concept of functional redundancy, at least under standardized in vitro conditions. Preferential mineralization of simple organic substrates in the rich fen and complex compounds in the poor fen was not observed. Similarly, no preference was given to ‘‘native’’ organic matter extracts derived from each fen, with microbial communities opting for the most bioavailable substrate. This study suggests that soil bacteria and fungi might be able to respond relatively rapidly to shifts in vegetation communities and subsequent changes in the quality of carbon substrate additions to peatlands associated with environmental and climatic change.

Corrosion behavior and characterization of plasma nitrided and borided AISI M2 steel

This study investigates the corrosion behaviors of plasma nitrided (PN) and borided AISI M2 steels. The PN process was carried out in a dc-plasma system at a temperature of 923K for 6 h in a gas mixture of 80%N2-20%H2 under a constant pressure of 5 mbar. The boriding process was carried out in Ekabor-II powder at a temperature of 1223K for 6 h. X-ray diffraction analysis on the surface of the PN and borided steels revealed the presence of FeB, Fe2B, CrB, MoB, WB, FeN, Fe2N, Fe3N and Fe4N compounds. Corrosion surfaces of the samples were analyzed using a SEM microscopy and X-ray energy dispersive spectroscopy EDS. The corrosion resistance of PN and borided AISI M2 steel is higher compared with that of untreated AISI M2 steel. Corrosion resistances of the PN and borided AISI M2 steel increased the 4-6- fold.

Bis(imino)pyridine Iron Dinitrogen Compounds Revisited: Differences in Electronic Structure Between Four- and Five-Coordinate Derivatives.

The electronic structures of the four- and five-coordinate aryl-substituted bis(imino)pyridine iron dinitrogen complexes, ((iPr)PDI)FeN(2) and ((iPr)PDI)Fe(N(2))(2) ((iPr)PDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N=CMe)(2)C(5)H(3)N), have been investigated by a combination of spectroscopic techniques (NMR, Mössbauer, X-ray Absorption and X-ray Emission) and DFT calculations. Homologation of the imine methyl backbone to ethyl or isopropyl groups resulted in the preparation of the new bis(imino)pyridine iron dinitrogen complexes, ((iPr)RPDI)FeN(2) ((iPr)RPDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N=CR)(2)C(5)H(3)N; R = Et, (i)Pr), that are exclusively four coordinate both in the solid state and in solution. The spectroscopic and computational data establish that the ((iPr)RPDI)FeN(2) compounds are intermediate spin ferrous derivatives (S(Fe) = 1) antiferromagnetically coupled to bis(imino)pyridine triplet diradical dianions (S(PDI) = 1). While this ground state description is identical to that previously reported for ((iPr)PDI)Fe(DMAP) (DMAP = 4-N,N-dimethylaminopyridine) and other four-coordinate iron compounds with principally σ-donating ligands, the d-orbital energetics determine the degree of coupling of the metal-chelate magnetic orbitals resulting in different NMR spectroscopic behavior. For ((iPr)RPDI)Fe(DMAP) and related compounds, this coupling is strong and results in temperature independent paramagnetism where a triplet excited state mixes with the singlet ground state via spin orbit coupling. In the ((iPr)RPDI)FeN(2) family, one of the iron SOMOs is essentially d(z2) in character resulting in poor overlap with the magnetic orbitals of the chelate, leading to thermal population of the triplet state and hence temperature dependent NMR behavior. The electronic structures of ((iPr)RPDI)FeN(2) and ((iPr)PDI)Fe(DMAP) differ from ((iPr)PDI)Fe(N(2))(2), a highly covalent molecule with a redox non-innocent chelate that is best described as a resonance hybrid between iron(0) and iron(II) canonical forms as originally proposed in 2004.

Bis(imino)pyridine Iron Dinitrogen Compounds Revisited: Differences in Electronic Structure Between Four- and Five-Coordinate Derivatives.

The electronic structures of the four- and five-coordinate aryl-substituted bis(imino)pyridine iron dinitrogen complexes, ((iPr)PDI)FeN(2) and ((iPr)PDI)Fe(N(2))(2) ((iPr)PDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N=CMe)(2)C(5)H(3)N), have been investigated by a combination of spectroscopic techniques (NMR, Mössbauer, X-ray Absorption, and X-ray Emission) and DFT calculations. Homologation of the imine methyl backbone to ethyl or isopropyl groups resulted in the preparation of the new bis(imino)pyridine iron dinitrogen complexes, ((iPr)RPDI)FeN(2) ((iPr)RPDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N=CR)(2)C(5)H(3)N; R = Et, (i)Pr), that are exclusively four coordinate both in the solid state and in solution. The spectroscopic and computational data establish that the ((iPr)RPDI)FeN(2) compounds are intermediate spin ferrous derivatives (S(Fe) = 1) antiferromagnetically coupled to bis(imino)pyridine triplet diradical dianions (S(PDI) = 1). While this ground state description is identical to that previously reported for ((iPr)PDI)Fe(DMAP) (DMAP = 4-N,N-dimethylaminopyridine) and other four-coordinate iron compounds with principally σ-donating ligands, the d-orbital energetics determine the degree of coupling of the metal-chelate magnetic orbitals resulting in different NMR spectroscopic behavior. For ((iPr)RPDI)Fe(DMAP) and related compounds, this coupling is strong and results in temperature independent paramagnetism where a triplet excited state mixes with the singlet ground state via spin orbit coupling. In the ((iPr)RPDI)FeN(2) family, one of the iron singly occupied molecular orbitals (SOMOs) is essentially d(z(2)) in character resulting in poor overlap with the magnetic orbitals of the chelate, leading to thermal population of the triplet state and hence temperature dependent NMR behavior. The electronic structures of ((iPr)RPDI)FeN(2) and ((iPr)PDI)Fe(DMAP) differ from ((iPr)PDI)Fe(N(2))(2), a highly covalent molecule with a redox noninnocent chelate that is best described as a resonance hybrid between iron(0) and iron(II) canonical forms as originally proposed in 2004.

Structural characterization of sputtered single-phase γ‴ iron nitride coatings

Single-phase γ‴-FeN films were deposited by d.c. magnetron sputtering in a reactive Ar/N 2 atmosphere. The films were characterized by X-ray diffraction, scanning and transmission electron microscopies, electron energy-loss and Mössbauer spectroscopy. The average lattice parameter of the γ‴ cubic cell is 0.455 nm. Microstructure studies by electron microscopies revealed nanostructured columnar films with no preferential orientation. Diffraction peak intensities (X-ray and electron diffraction) are close to the theoretical values for a ZnS-type structure while profile analysis of the X-ray diffraction pattern using Rietveld refinement method demonstrated that the γ‴-phase is of ZnS-type. The energy-loss near-edge structures of N K-edge of the γ‴-phase is similar to those of the ZnS-type γ″-phase suggesting an identical local atomic environment for N atoms. On the contrary, Mössbauer spectra of both structures are different, which is understood as a consequence of numerous vacancies in the γ‴ structure. Investigations of magnetic properties showed that the γ‴-FeN compound is paramagnetic from room temperature to 2 K. The main conclusion of this work is that the γ‴-FeN phase is of ZnS-type, and not of NaCl-type as it is usually reported.

Optical and Magnetic Properties of Fe-Doped GaN Diluted Magnetic Semiconductors Prepared by MOCVD Method

Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method (MOCVD). Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and Fe-N compounds which we have not detected.

Striped domains in soft magnetic FeNiN thin films

FeNiN thin films with good soft magnetic properties were synthesized on Si (1 0 0) substrates at 473 K by RF magnetron sputtering; all the films have a thickness of around 500 nm. The dependence of phase structure and magnetic properties on nickel concentrations and RF power were systematically investigated. With increasing nickel contents from XNi = 5.0% to XNi = 65.5%, FeNiN thin films deposited at turn from a main bcc α-(Fe,Ni) phase coexisting with γ′-phase to fcc γ-(FeNi3)4N phase. With the RF power larger than 160 W, the samples deposited at all show clear reproducible striped domains at the films' surfaces, which is explained by the high enough perpendicular anisotropy and the small stress in the film. A completely ordered structure of (FeNi)N0.0324-phase forms at PW = 300 W. The FeNiN thin films prepared at different RF power show smooth surfaces and good soft magnetic properties compared with corresponding FeN compounds. The optimum soft magnetic properties with MS of ∼ 1900 emu cm−3, HC of ∼1 Oe are obtained at and PW = 300 W at 473 K.

Ab initio investigation of the electronic structure and the magnetic trends within equiatomic FeN

The magnetic properties of equiatomic FeN nitride have been investigated within the density functional theory (DFT) using the augmented spherical wave method (ASW). Calculation of the energy versus volume in hypothetic rocksalt (RS), zinc-blende (ZB) and wurtzite (W) types structures show that the RS-type structure is preferred. At equilibrium, energy/volume spin polarized calculations indicate that the ground state of RS-FeN is ferromagnetic with a high moment, while ZB-FeN and W-FeN are non magnetic. The magnetovolume effects with respect to the Slater–Pauling–Friedel model are discussed. Analyses of the electronic structure (density of states and chemical bonding) are reported. A discussion of the structural and magnetic properties of FeN compound is given with respect to N local environment of Fe.