Mössbauer isomer-shift of ferrous iron impurities in ionic and covalent binary compounds

Gunnlaugsson, H. P.; Masenda, H.

doi:10.1016/j.jpcs.2018.12.037

Cited by 4 publications

(5 citation statements)

References 31 publications

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“…The hyperfine parameters of the doublet were determined as δ = 0.58(1) mm s −1 and the average quadrupole splitting ΔE Q = 1.48(1) mm s −1 at RT. The isomer shift value is close to the one expected for dilute high-spin Fe 2+ (δ = 0.47 mm s −1 ) estimated using the semi-empirical model developed by Gunnlaugsson and Masenda [48] from 22 compounds with δ values showing a standard deviation of ±0.1 mm s −1 . The model takes into account nearest neighbour distances and electronegativity of the hosts and allows the assignment of this component to substitutional Fe 2+ .…”

Section: Resultssupporting

confidence: 83%

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

et al. 2022

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Charge states and lattice sites of Fe ions in virgin and Mn-doped Al x Ga1-x N samples were investigated using 57Fe emission Mössbauer spectroscopy following radioactive 57Mn+ ion implantation at ISOLDE, CERN. In the undoped Al x Ga1-x N, Fe2+ on Al/Ga sites associated with nitrogen vacancies and Fe3+ on substitutional Al/Ga sites are identified valency states in undoped Al x Ga1-x N. With Mn doping, the contribution of Fe3+ is considerably reduced and replaced instead by a corresponding emergence of a single line component consistent with Fe4+ on Al/Ga sites. Density functional theory calculations confirm the Fe4+ charge state as stabilised by the presence of substitutional Mn2+ in its vicinity. The completely filled spin up orbitals in Mn2+ (3d 5) are expected to enhance magnetic exchange interactions. The population of the Fe4+ state is less pronounced at high Al concentration in Al x Ga1-x N:Mn, a behaviour attributable to hybridisation effects of 3d states to the semiconductor bands which weakens with increasing (decreasing) Al (Ga) content. Our results demonstrate that co-doping promotes the co-existence of unusual charge states of Fe4+ and Mn2+, whereas their trivalent charge states prevail with either transition metal incorporated independently in III-nitrides. Co-doping thus opens up a new avenue for tailoring novel magnetic properties in doped semiconductors.

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Section: Resultssupporting

confidence: 83%

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

et al. 2022

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“…The empirical model relies mainly on the nearest-neighbor distances and Pauling electronegativity (Δχ P < 2). 70 The performed calculations show that after relaxation, local distortions affecting Fe:Ti bond lengths are anisotropic and higher than what have been observed with calculations performed by Rodri ́guez-Torres et al, 67 however slightly lower (1.94 Å) than the previously published XAFS data (Fe:Ti) (1.97 Å). 71 The difference in bond lengths could be related to the displacement, which is symmetric in the PBE approximation.…”

Section: ■ Results and Discussionmentioning

confidence: 46%

“…The model predicts room-temperature isomer shift values for Fe 2+ in metal oxides. The empirical model relies mainly on the nearest-neighbor distances and Pauling electronegativity (Δχ P < 2) …”

Section: Resultsmentioning

confidence: 99%

“…Experimental data is for Fe 2+ component taken at RT. δA is the isomer shift (IS) based on the empirical model70 . Moreover, the performed calculations are done at 0 K and if there is a low crystal field splitting near the probe then average values of the QS are used.…”

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confidence: 99%

“…Experimental data is for the Fe 2+ component taken at RT. δ A is the isomer shift (IS) based on the empirical model 70. Mark ◇ is added for a 3 × 3 × 1 SC.…”

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confidence: 99%

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Experimental and Theoretical Study of Electronic and Hyperfine Properties of Hydrogenated Anatase (TiO₂): Defect Interplay and Thermal Stability

et al. 2020

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Performance of TiO2-based materials is highly dependent on the electronic structure and local defect configurations. Hence, a thorough understanding of defects interaction plays a key role. In this study we report on the results from emission 57 Fe Mössbauer Spectroscopy experiments, using dilute 57 Mn implantation into pristine (TiO2) and hydrogenated anatase held at temperatures between 300-700 K. Results of the electronic structure and local environment are complemented with ab-initio calculations. Upon implantation both Fe 2+ and Fe 3+ are observed in pristine anatase, where the latter demonstrates the spin-lattice relaxation. The spectra obtained for hydrogenated anatase show no Fe 3+ contribution, suggesting that hydrogen acts as a donor. Due to the low threshold, hydrogen diffuses out of the lattice. Thus showing a dynamic behaviour on the time scale of the 57 Fe 14.4 keV state. The surrounding oxygen vacancies favor the high-spin Fe 2+ state. The sample treated at room temperature shows two distinct processes of hydrogen motion. The motion commences with the interstitial hydrogen, followed by switching to the covalently bound state. Hydrogen out-diffusion is hindered by bulk defects, which could cause both processes to overlap. Supplementary UV-Vis and electrical conductivity measurements show an improved electrical conductivity and higher optical absorption after the hydrogenation. X-ray photoelectron spectroscopy at room temperature reveals that the sample hydrogenated at 573 K shows presence of both Ti 3+ and Ti 2+ states. This could imply that a significant amount of oxygen vacancies and -OH bonds are present in the samples. Theory suggests that in the anatase sample implanted with Mn(Fe), probes were located near equatorial vacancies as next-nearest-neighbours, whilst a metastable hydrogen configuration is responsible for the annealing behaviour. The obtained information provides a deep insight into elusive hydrogen defects and their thermal stability.

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Metal-insulator transition in crystalline V2O3 thin films probed at atomic-scale using emission Mössbauer spectroscopy

Gunnlaugsson

Ólafsson

et al. 2020

Thin Solid Films

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Mössbauer isomer-shift of ferrous iron impurities in ionic and covalent binary compounds

Cited by 4 publications

References 31 publications

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

Experimental and Theoretical Study of Electronic and Hyperfine Properties of Hydrogenated Anatase (TiO₂): Defect Interplay and Thermal Stability

Metal-insulator transition in crystalline V2O3 thin films probed at atomic-scale using emission Mössbauer spectroscopy

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Mössbauer isomer-shift of ferrous iron impurities in ionic and covalent binary compounds

Cited by 4 publications

References 31 publications

Unusual charge states and lattice sites of Fe in Al x Ga1−x N:Mn

Unusual charge states and lattice sites of Fe in Al x Ga1−x N:Mn

Experimental and Theoretical Study of Electronic and Hyperfine Properties of Hydrogenated Anatase (TiO2): Defect Interplay and Thermal Stability

Metal-insulator transition in crystalline V2O3 thin films probed at atomic-scale using emission Mössbauer spectroscopy

Contact Info

Product

Resources

About

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

Unusual charge states and lattice sites of Fe in Al_xGa_1−xN:Mn

Experimental and Theoretical Study of Electronic and Hyperfine Properties of Hydrogenated Anatase (TiO₂): Defect Interplay and Thermal Stability