Table of hyperfine fields for impurities in Fe,Co, Ni and Gd

All data available in the literature for the impurity hyperfine fields in Fe, Co, Ni and Gd matrices are collected and tabulated. The literature search was carried out for all references listed in Physics Abstracts on papers published till the end of December 1978. The present work is an extension of similar earlier compilations [1–6]. The data are arranged in ten columns as explained below:     

Theg-factor of the 659 keV level in117In

We have measured theg-factor of the 659 keV, 3/2⁺, state in¹¹⁷In, using time differential perturbed angular correlation technique. The spin precession of this state was measured in an external field of 20·2 kG. The values of the Larmor precession frequencyω and theg-factor are obtained to be (60·1±0·3)10⁶ rads/sec and 0·625±0·007 respectively.     

Measurements of magnetic moments of Tc isotopes and the hyperfine field of Tc in Fe and Ni

We report measurements of nuclear magnetic resonance on oriented nuclei (NMR-ON) on⁹⁴Tc (I=7⁺,T _1/2=4.9 h),⁹⁵Tc (I =9/2⁺,T _1/2=20 h) and⁹⁶Tc (I =7⁺,T _1/2=4.3 d) in Fe and on⁹⁵Tc and⁹⁶Tc in Ni. In order to elucidate the discrepancies on the hyperfine field of TcFe in the literature, the resonances were measured with high precision as a function of the external magnetic field B_ext up to 2.0 T. In addition, TDPAC measurements were performed on⁹⁹TcFe at T=300 K and 13 K. TheT=0 K hyperfine fields of Tc in Fe and Ni were determined to be –314(3) kG and –51.8(5) kG, respectively. The g-factors of⁹³Tc,⁹⁴Tc,⁹⁵Tc,⁹⁶Tc and⁹⁹Tc(E=181 keV;I =5/2⁺) are redetermined as g(⁹³Tc)=1.405(14), g(⁹⁴Tc)=0.731(7),g(⁹⁵Tc)=1.321(13), g(⁹⁶Tc)=0.727(7), g(⁹⁹Tc)=1.390(17).We wish to thank E. Smolic and G. Seewald for experimental help. This work was funded by the German Federal Minister for Research and Technology (BMFT) under the contract number 06TM353/TP 4, by the Deutsche Forschungsgemeinschaft (DFG) under the contract numbers Ha 1282/3-1,2, and, partly, by the Kernforschungszentrum, Karlsruhe.     

Theoretical study of the environmental effects on the hyperfine fields of Ni and Fe in Ni0.75Fe0.25

The dependence of the hyperfine fields B_hf of Ni and Fe in Ni_0.75Fe_0.25 on the surrounding atomic configuration has been studied by performing charge selfconsistent 6 shell-cluster Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) bandstructure calculations. By replacing the CPA- scatterers in the various shells around the central atom by Ni - or Fe-atoms, respectively, it could be shown that the hyperfine fields vary linearly with the number of Fe-atoms within a given shell and that the changes of B_hf due to simultaneous changes of the atomic configurations of different shells are additive. The changes of the hyperfine fields upon ordering of Ni_0.75Fe_0.25 solid solution as deduced from our calculations agrees reasonably well with experiments.     

The magnetic hyperfine field at Cu in Fe,Co and Ni and the magnetic moment of the 41 keV, 2+ state of62Cu

The magnetic hyperfine interaction of Cu in Fe, Co and Ni was studied by means of the γ-γ perturbed angular correlation method using⁶²Zn(⁶²Cu) as a probe. With the publishedg-factor (g=+0.661(12)) of the 41 keV, 2⁺ state hyperfine fields ofB _HF=16.95(51) T,B _HF=13.15(41) T andB _HF=4.05(30) T atT=0 K for Cu in Fe, Co and Ni are derived, respectively. The systematic discrepancy of these values with several independent measurements of these hyperfine fields is removed by deriving a new value ofg=0.55(5) for the 41 keV, 2⁺ state of⁶²Cu.     

A theoretical study of the hyperfine fields of Fe and Co in ferromagneticbcc Fe x Co1−x

The hyperfine fields of Fe and Co in the substitutionally disorderedbcc alloy system Fe _x Co_1−x due to the Fermi contact interaction have been studied by means of charge self-consistent cluster Korringa-Kohn-Rostoker-Coherent Potential Approximation- (KKR-CPA) band structure calculations. The contribution to the Fermi contact hyperfine field due to core polarisation was found to be proportional to the local moment for Fe as well as for Co throughout the concentration range. On the other hand, the contributions of the conduction band did not show such a simple behavior, but were found to be dominated by the population of the s-bands for spin up and down. These findings are completely analogous to those obtained in a recent study of the ferromagnetic alloy systems Fe _x Ni_1−x and Fe _x Cr_1−x . To investigate the importance of relativistic effects on the Fermi contact hyperfine fields, the corresponding hyperfine matrix elements have been calculated nonrelativistically as well as fully relativistically. The results of the present work are compared with experiment as well as to theoretical data on related alloy systems.     

The hyperfine field of99Tc in iron

The magnetic hyperfine field at⁹⁹Tc impurities in Fe has been measured to be ¦H _hf¦=325 (7) kGauss at 298 °K. The technique of time-differential perturbed angular correlations on the 181 keV state of⁹⁹Tc was used.     

Temperature dependence of the hyperfine field of Tc in Fe

Using BaF₂ scintillation counters we made a series of DPAC measurements on⁹⁹TcFe in the temperature range 77 < T < 1020 K. Our results at room temperature are consistent with earlier measurements of Raghavan and Raghavan. Contrary to earlier suppositions, H_hf(T) does not have an anomalous temperature dependence like that of OsFe.     

Nuclear level structure of99Tc

The gamma rays of⁹⁹Tc excited through negatron decay of⁹⁹Mo have been studied by internal conversion spectroscopy, using a high resolution double focusing beta-ray spectrometer. Conversion electrons were observed for all transitions reported before. In addition a new gamma ray of energy 989.37±1.02 keV could be identified and ascribed for the first time to the decay of⁹⁹Mo. Gamma-ray energies have been determined with high precision. Multipolarity data, obtained from the measurements of absolute or ratio of conversion coefficients of gamma rays, were utilized for assigning possible spins and parities to the levels of⁹⁹Tc. From our present data combined with other studies spins and parities; 7/2+, 1/2?, 5/2+, 3/2?, 3/2+ and 5/2? have been given to the 140, 142, 181, 514, 922 and 1131 keV levels respectively. The experimental level scheme is discussed in terms of theoretical predictions.     

The hyperfine magnetic field at57Fe and181Ta in Hf(Fe1−x Co x )2 system

The hyperfine magnetic field at⁵⁷Fe in the ferromagnetic Laves compounds Hf(Fe_1?x Co _x )₂ was measured by the Mössbauer effect method. The substitution of Fe atoms by Co atoms induces a gradual change ofB _hf(Fe) and a decrease in the magnetic moment values in Fe?Co sublattice. The perturbed angular correlation measurements of¹⁸¹Ta were carried out forX=0,X=0.1,X=0.55 at 300 K, andX=0.4 atT=400°C. An abrupt change ofB _hf (Ta) in 0<X<0.1 was observed.     

Calculated hyperfine fields of light interstitials in Fe

Super-cell band structure calculations with the Korringa-Kohn-Rostoker method in the framework of the local-spin-density approximation are performed on ferromagnetic iron with typical elements (B, C andN) at the octahedral interstitial sites for the purpose of studying hyperfine fields of light interstitials. Lattice relaxations around the interstitial atoms are allowed in these calculations. Calculated hyperfine fields of these interstitial impurities are in better agreement with experimental values than the results obtained previously for unrelaxed lattices, showing that the inclusion of the lattice relaxation is crucial in these systems.     

The 1377 keV level in 57Co

The lifetime of the 1377 keV level has been measured using Doppler shift and direct timing techniques. The Doppler shift measurement provided a limit τ > 3 ps and the direct timing measurment gave τ = 27 ± 14ps. The lifetime is compared with the predictions of various models for the structure of ⁵⁷Co.     

Mössbauer effect study of the hyperfine fields and isomer shift of ordered Fe−Co alloys

The influence of Co concentration on the⁸⁷Fe hyperfine magnetic field and isomer shift in ordered and disordered FeCo alloys in the composition range (34–70) at .% is studied. It is shown that the model which assumes an additivity of the hyperfine field perturbation from solutes in the first two nearest neighbour shells of Fe nucleus very well describes the experimental data.