μ+SR study of vacancies in thermal equilibrium in ferromagnets

Fürderer, K.; Döring, K. P.; Gladisch, M.; Haas, N.; Herlach, D.; Major, J.; Mundinger, H. J.; Rosenkranz, J.; Schäfer, Wolfgang; Schimmele, L.; Schmolz, Manfred; Schwarz, Winfried H.; Seeger, A.

doi:10.1007/bf02401543

Cited by 16 publications

(15 citation statements)

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“…It seems that accounting for the presence of O impurities in Fe samples in very low concentrations (≪ 1 appm, i.e., below detection threshold) allows us to quantitatively reproduce experimental G f ðVÞ Fe in ferromagnetic α-Fe [4,5] from DFT data. It would be interesting to perform these experiments again, paying particular attention to the O concentration, the effect of VX 2 clusters, and the nonlinear variation of G f ðVÞ jFe-CNO with temperature.…”

Section: Vxmentioning

confidence: 84%

“…[4] and ½X sol T . Assuming that G f ðVÞ jFe-CNO varies linearly with temperature and that muons respond in the same way to isolated V and vacancy-solute clusters, we extrapolate H f from our results in the narrow temperature range where the μSR experiment is conducted (925 K < T < 1000 K).…”

Section: Vxmentioning

confidence: 98%

“…Fürderer et al [4] have measured G f ðVÞ in ferromagnetic α-Fe using the μSR technique: G f ðVÞ ¼ 1.66 AE 0.07 − ð1.64 AE 0.67ÞkT eV. The sample impurity contents are assumed to be constant during the μSR experiment and equal to: ½C ¼ 0.1 appm, ½N ¼ 2.8 appm, ½O ¼ 11 appm [48].…”

Section: Vxmentioning

confidence: 99%

“…In ferromagnetic α-Fe, there are only two measurements of the V formation enthalpy: H f ¼ 1.66 AE 0.1 eV from muons spin rotation (μSR) [4] and H f ¼ 2.00 AE 0.2 eV from positron annihilation spectroscopy (PAS) in carbondoped samples [5]. In the paramagnetic state, H f is estimated between 1.40 and 2.00 eV [5][6][7][8][9].…”

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Equilibrium Vacancy Concentration Driven by Undetectable Impurities

et al. 2015

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By means of ab initio calculations combined to statistical mechanics, we provide new evidence that an experimentally undetectable tiny amount of impurities can be responsible for drastic changes in vacancy concentrations ([V]), inducing large deviations from an Arrhenius law even at low temperature. It is the case of O and N in α-Fe. The present finding is fully compatible with existing experiments, and changes the previous common vision that C has the dominant effect. This study provides a route for bridging the longstanding theoretical-experimental gap on the prediction of [V] in metals.

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Section: Vxmentioning

confidence: 84%

Section: Vxmentioning

confidence: 98%

Section: Vxmentioning

confidence: 99%

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confidence: 99%

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Equilibrium Vacancy Concentration Driven by Undetectable Impurities

et al. 2015

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“…All three techniques are based on the fact that in a ferromagnet the magnetic field acting on the m magnetic moment in a vacancy differs from that acting on a m in an interstice. a) m spin rotation in a demagnetized sample [45]. The spins of m trapped in vacancies precess in their local fields with angular velocities that differ from that of ªfreeº m .…”

Section: High-temperature M Srmentioning

confidence: 99%

Lattice Vacancies in High-Purity α-Iron

Seeger

1998

phys. stat. sol. (a)

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The paper is both a review of the properties of vacancies in high‐purity α‐iron and an original contribution. In the review part it is shown that self‐diffusion in α‐iron occurs by the vacancy mechanism, that the sum of the monovacancy formation and migration enthalphies in the magnetically fully ordered state is HF1V + HM1V = (2.91 ± 0.04) eV, and that for the monovacancy formation enthalpy 1.61 eV ≤ HF1V ≤ 1.75 eV holds. The result for the monovacancy migration energy, HM1V = (1.23 ± 0.11) eV, excludes with certainty the attribution of Stage‐III recovery to vacancy migration and supports the view that the Stage‐III defect is a self‐interstitial. It is shown that at elevated temperatures positrons trapped in vacancies in body‐centred cubic iron may escape from them. The binding energy of positrons to the vacancies is estimated to be about 1.1 eV. This estimate is in agreement with the analysis of the high‐temperature trapping of positive muon by vacancies, which in the present case proved to be the most sensitive technique for detecting vacancies present in thermal equilibrium.

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A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in ?-Iron and Its Diluted Alloys

Blythe

Kronmüller²,

Seeger³

et al. 2000

phys. stat. sol. (a)

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This review presents a comprehensive survey on intensive studies performed during the last decades on point defect reactions on a-iron (a-Fe) and its diluted alloys. Our intention is to give an actual account of the knowledge accumulated on this subject, as it has been obtained predominantly by means of the magnetic after-effect (MAE) spectroscopy. After a concise introduction into the theoretical and experimental fundamentals of this technique, the main concern is focused on the presentation and detailed discussion of the MAE spectra arising ± ± after low-temperature electron (e À )-or neutron(n)-irradiation and subsequent annealing ± ± in: (i) high-purity a-Fe and a-Fe doped with (ii) substitutional solutes (like Ni, V, Al, Cu, Ti, Be, Si, Mn, . . .) or (iii) interstitial solutes (like O, H, C, N). During the course of systematic annealing treatments, these respective spectra undergo dramatic variations at specific temperatures thereby revealing in great detail the underlying intrinsic reactions of the radiation-induced defects, i.e., reorientation, migration, clustering, dissolution and finally annihilation. In alloyed Fe systems the corresponding reaction sequences are even multiplied due to additional interactions between defects and solute atoms. Most valuable information concerning formation-, dissociation-and binding enthalpies of small, mixed clusters (of the type C i V k , N i V k ; i; k ! 1) has been obtained in highpurity a-Fe base material which, after charging with C or N, had been e À -irradiated. Concerning the basic recovery mechanisms in a-Fe, two complementary results are obtained from the analysis of the various systems: (i) in high-purity and substitutionally alloyed a-Fe the recovery in Stage-III (200 K) is governed by a three-dimensionally migrating (H M I 0:56 eV) stable interstitial (dumbbell); (ii) following the formation and dissociation kinetics of small clusters (C 1 V k , N 1 V k ) in interstitially alloyed a-Fe the migration enthalpy of the monovacancy must hold the following relation H M N (0.76 eV) < H M C (0.84 eV) < H M V1 . These results are in clear agreement with the socalled two-interstitial model (2IM) in a-Fe ± a conclusion being further substantiated by a systematic comparison with the results obtained from nonrelaxational techniques, like i.e. positron annihilation (PA), which by their authors are preferentially interpreted in terms of the one-interstitial model (1IM).Die vorliegende Arbeit gibt einen umfassenden Ûberlick u È ber die wa È hrend der letzten Jahrzehnte durchgefu È hrten, eingehenden Untersuchungen der Punktfehler-Eigenschaften in a-Eisen (a-Fe) und verdu È nnten Fe-Legierungen. Demgema È û ist diese Zusammenfassung gedacht als ein dem gegenwa Èrtigen Kenntnisstand entsprechender Rechenschaftsbericht u È ber die auf diesem Gebiet, hauptsa È chlich mit Hilfe der magnetischen Nachwirkungs (MNW) ± ± Spektroskopie, gewonnenen, tiefreichenden Einsichten in diesen Problemkreis. Nach einer kurzen Einfu È hrung in die theoretischen und experimentellen Grundlagen di...

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μ+SR study of vacancies in thermal equilibrium in ferromagnets

Cited by 16 publications

References 6 publications

Equilibrium Vacancy Concentration Driven by Undetectable Impurities

Equilibrium Vacancy Concentration Driven by Undetectable Impurities

Lattice Vacancies in High-Purity α-Iron

A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in ?-Iron and Its Diluted Alloys

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