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The lattice sites, valence states, resulting magnetic behaviour and spin–lattice relaxation of Fe ions in GaN and AlN were investigated by emission Mössbauer spectroscopy following the implantation of radioactive 57 Mn + ions at ISOLDE/CERN. Angle dependent measurements performed at room temperature on the 14.4 keV γ -rays from the 57 Fe Mössbauer state (populated from the 57 Mn β − decay) reveal that the majority of the Fe ions are in the 2+ valence state nearly substituting the Ga and Al cations, and/or associated with vacancy type defects. Emission Mössbauer spectroscopy experiments conducted over a temperature range of 100–800 K show the presence of magnetically split sextets in the “wings” of the spectra for both materials. The temperature dependence of the sextets relates these spectral features to paramagnetic Fe 3+ with rather slow spin–lattice relaxation rates which follow a T 2 temperature dependence characteristic of a two-phonon Raman process. [ABSTRACT FROM AUTHOR]

Emission Mössbauer spectroscopy has been utilised to characterize dilute Fe impurities in In O following implantation of Mn ( T = 1.5 min.) at the ISOLDE facility at CERN. From stoichiometry considerations, one would expect Fe to adopt the valence state 3 + , substituting In , however the spectra are dominated by spectral lines due to paramagnetic Fe. Using first principle calculations in the framework of density functional theory (DFT), the density of states of dilute Fe and the hyperfine parameters have been determined. The hybridization between the 3d-band of Fe and the 2p band of oxygen induces a spin-polarized hole on the O site close to the Fe site, which is found to be the cause of the Fe state in In O. Comparison of experimental data to calculated hyperfine parameters suggests that Fe predominantly enters the 8b site rather than the 24d site of the cation site in the Bixbyite structure of In O. A gradual transition from an amorphous to a crystalline state is observed with increasing implantation/annealing temperature. [ABSTRACT FROM AUTHOR]

States of dilute Fe in SnO have been monitored using Fe emission Mössbauer spectroscopy following implantation of Mn ( T = 85.4 s) in the temperature range from 143 K to 711 K. A sharp annealing stage is observed at ~330 K where the Fe/Fe ratio shows a marked increase. It is suggested that this annealing stage is due to the dissociation of Mn-V pairs during the lifetime of Mn; the activation energy for this dissociation is estimated to be 0.9(1) eV. Fe is found in a paramagnetic state showing spin-lattice relaxation rates consistent with an expected T dependence derived for a Raman process. In addition, a sharp lined doublet in the Mössbauer spectra is interpreted as due to recoil produced interstitial Fe. [ABSTRACT FROM AUTHOR]

The valence state and annealing reactions of Mn/Fe in single crystalline α-AlO have been determined following low fluence (<10 cm) 60 keV implantations of Mn (T = 1.5 min) and emission Mössbauer spectroscopy on the Fe daughter nuclei in the temperature range from 110-700 K. At 110 K, most probe atoms are found in the Fe state in amorphous surroundings due to the implantation damage. A fraction of the Fe is found in cubic environment, possibly nano-precipitates of η-AlO. This site is found to disappear from the spectra above 500 K. Annealing of the damage sites at increasing temperatures leads first to increased incorporation of the probe atoms as Fe on Al sites, and, above room temperature, also as Fe. The Fe sub-spectrum is masked by slow paramagnetic relaxations following a T dependence, as expected for a two-phonon Raman process. Our data is consistent with data from Co and Fe implantations, suggesting a general increase in the average Fe valence state with lower implantation dose and negligible annealing reactions at room temperature. [ABSTRACT FROM AUTHOR]

Ion implantation provides a precise method of incorporating dopant atoms in semiconductors, provided lattice damage due to the implantation process can be annealed and the dopant atoms located on regular lattice sites. We have undertaken Fe emission Mössbauer spectroscopy measurements on GaAs and GaP single crystals following implantation of radioactive Mn ions, to study the lattice sites of the implanted ions, the annealing of implantation induced damage and impurity-vacancy complexes formed. The Mössbauer spectra were analyzed with four spectral components: an asymmetric doublet (D1) attributed to Fe atoms in distorted environments due to implantation damage, two single lines, S1 assigned to Fe on substitutional Ga sites, and S2 to Fe on interstitial sites, and a low intensity symmetric doublet (D2) assigned to impurity-vacancy complexes. The variations in the extracted hyperfine parameters of D1 for both materials at high temperatures ( T > 400 K) suggests changes in the immediate environment of the Fe impurity atoms and different bonding mechanism to the Mössbauer probe atom. The results show that the annealing of the radiation induced damage is more prominent in GaAs compared to GaP. [ABSTRACT FROM AUTHOR]

• Local metal-insulator transition (MIT) in V 2 O 3 thin films is probed at the atomic scale. • The 57Fe online emission mössbauer spectroscopy was applied. • The oxygen vacancies are proved to be common in the V 2 O 3 thin films. • Epitaxial strain plays a decisive role in controlling the global MIT of thin films. • The early-stage dynamics of the MIT of V 2 O 3 thin films was confirmed. Microscopic understanding the metal-to-insulator transition (MIT) in strongly correlated materials is critical to the design and control of modern "beyond silicon" Mott nanodevices. In this work, the local MIT behaviors in single crystalline V 2 O 3 thin films were probed on an atomic scale by online 57Fe emission Mössbauer spectroscopy (eMS) following dilute (< 10−3 at.%) implantation of 57Mn+ (T 1 / 2 = 90 s). Both the epitaxial and the textured V 2 O 3 thin films grown by direct current magnetron sputtering were studied. Three structural components were resolved and identified in the eMS spectra with parameters characteristic of Fe in the 2+ valence state, which are attributable to Fe in either lattice damage or structural defects and Fe in the intrinsic crystal structure of V 2 O 3 , respectively. The results prove that the oxygen vacancies are common in the V 2 O 3 thin films. With co-existence of both the non-stoichiometry and epitaxial strain in the thin films, the epitaxial strain plays a dominant role in controlling the global MIT properties of the film. The atomic scale structural transition captured by the eMS affirms the early-stage dynamics of the MIT of V 2 O 3 thin film reported previously. These results approve the feasibility to tune the electronic transport of the V 2 O 3 thin films for the next-generation Mott nanodevices by the epitaxial strain via the sample growth parameters. [ABSTRACT FROM AUTHOR]

The change in the Curie temperature of single crystalline garnet Y 3 Fe 5 O 12 (YIG) sample due to lattice damage induced by ion implantation has been investigated in 57Fe emission Mössbauer Spectroscopy (eMS) following implantation of 57Mn (T ½ = 1.5 min). The Mössbauer spectra analysis reveal high spin Fe3+ ions substituted on both the octahedral and the tetrahedral sites. Measurements in the temperature range 298 K–798 K show that average values of the magnetic hyperfine field are decreased by the implantation-induced damage on the local lattice structure of the YIG. The Curie temperature, however, is determined to be 651 ± 5 K, considerably higher than the value of bulk YIG (559 K). This is most likely due to lattice damage-induced changes on the spin configurations of YIG through a Fe A -O-Fe D distortion scheme. • Implanted Mn atoms enter Fe sites in Y 3 Fe 5 O 12 (YIG). • Implantation of YIG increases the local Curie temperature due to implantation damage. • Ion implantation is a possible method of tailoring magnetic properties in YIG. [ABSTRACT FROM AUTHOR]