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A detailed Mossbauer study of 170Yb diluted in CaF2 has been performed on CaF 2 (170Yb) absorbers as well as on CaF 2 (170Tm) sources. Various informations have been obtained about valency states of Ytterbium, relative proportions of the different sites, hyperfine parameters, relaxation of Yb3+, concentration and after decay effects etc— The isomer shift of Yb3+ and Yb2+ in cubic sites in CaF2 differ only by 0.29±0.10 mm s ; an accurate determination of the nuclear factor, g ( 170 Yb , 84 keV ) = 0.334±0.002 , has been derived from the slow relaxation Hf splitting of cubic Yb3+.

Resume Les resistivites electriques, les susceptibilites magnetiques et les deplacements isomeriques du spectre Mossbauer de quelques composes intermetalliques cubiques de l'ytterbium et d'elements diamagnetiques (YbIn 3 , YbSn 3 , YbPb 3 et YbAl 2 ) ont ete etudies et compares. L'etude thermomagnetique a ete effectuee entre 10 et 300 K. Les valeurs des susceptibilites sont tres faibles a temperature ambiante et YbSn 3 en particulier, est diamagnetique. Les resistivites electriques ont ete mesurees entre 4 et 300 K. Les valeurs a temperature ambiante sont voisines de celle de l'ytterbium. Le deplacement isomerique de la raie de resonance de 170 Yb relatif a l'ytterbium metal, a 4.2 K, est tres voisin de celui des composes YbIn 3 , YbSn 3 , YbPb 3 , et nettement plus negatif que celui concernant YbAl 2 .

A detailed Mossbauer study of 170Yb diluted in CaF2 has been performed on CaF 2 (170Yb) absorbers as well as on CaF 2 (170Tm) sources. Various informations have been obtained about valency states of Ytterbium, relative proportions of the different sites, hyperfine parameters, relaxation of Yb3+, concentration and after decay effects etc— The isomer shift of Yb3+ and Yb2+ in cubic sites in CaF2 differ only by 0.29±0.10 mm s ; an accurate determination of the nuclear factor, g ( 170 Yb , 84 keV ) = 0.334±0.002 , has been derived from the slow relaxation Hf splitting of cubic Yb3+.

The hf parameters and the relaxation rate of Yb 3+ in YbES are deduced from the 170 Yb Mossbauer spectra between 1·3 and 30 K. The shielding factors R ≅ 0·24 and σ 2 ≅ 0·61 are derived from the experiments. The thermal variation of the relaxation rate observed between 8 and 25 K shows an additional exponential term to the previously observed Orbach and Raman processes, which is attributed to an optical mode of phonons.

Mössbauer studies show an antiferromagnetic order in sternbergite, and confirm the existence of a magnetic coupling in cubanite. According to the Mössbauer spectra, in each of these compounds all the iron atoms are in the same crystallographic site and in the same valency state, but the local symmetry seems to be different in the two compounds., L'étude par effet Mössbauer a mis en évidence un ordre antiferromagnétique dans la sternbergite, et confirmé l'existence d'un couplage dans la cubanite. A l'intérieur d'un même composé l'effet Mössbauer n'a décelé qu'un seul type de site et d'état de valence pour les atomes de fer, mais la symétrie locale du site paraît différente d'un composé à l'autre., Imbert P., Wintenberger Micheline. Étude des propriétés magnétiques et des spectres d'absorption par effet Mössbauer de la cubanite et de la sternbergite. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 90, 3, 1967. pp. 299-303.

Mossbauer effect studies of divalent iron impurities substituting the metal ion at tetrahedral sites in cubic ZnS and hexagonal ZnS and CdS were performed. No indication of a static Jahn-Teller distortion for the isolated Fe 2+ ions was found. For the case when one next metal neighbor is also replaced by Fe 2+ or by another impurity a strong quadrupole splitting was visible already at room temperature.

A single crystal 〈111〉 platelet of the cubic perovskite KFeF3 has been submitted to a stress parallel to its plane. By this means, a single magnetic domain may be obtained in the magnetic region having a trigonal symmetry. By measuring the relative intensities of the Mossbauer lines, the orientation of the hyperfine field and of the electric field gradient tensor with respect to the plane of the platelet have been determined throughout the temperature range 4.2 ≦ T ≦ 110°K. Une lame monocristalline mince de la perovskite cubique KFeF3 taillee parallelement a un plan 〈111〉, est soumise a des forces de compression paralleles a son plan. II est possible d'obtenir ainsi, dans la zone magnetique a symetrie trigonale, un monodomaine magnetique. L'etude de l'intensite des raies Mossbauer permet alors de determiner I'orientstion du champ hyperfin et des axes du gradient de champ Plectrique par rapport an plan de la lame dans toute la zone de temperature (4,2 ≦ T ≦ 110°K).

In some magnetically ordered compounds, broadened Mossbauer spectra are interpreted as arising from hyperfine field (Hn) distributions. These distributions measured at several temperatures are used to determine both a possible distribution of transition temperatures in the sample as well as the set of curves of Hn as a function of temperature. The method of calculation is applied to ZnFe2O4. Les spectres Mossbauer elargis de certains composes magnetiques peuvent traduire des distributions du champ magnetique interne (Hn). Ayant determine les distributions de Hn a differentes temperatures, il est possible d'en deduire a la fois une eventuelle distribution de la temperature de transition (TN) dans l'echantillon et le reseau des courbes donnant l'evolution thermique de Hn. Nous avons applique la methode a l'etude de ZnFe2O4.

Resume Le compose antiferromagnetique FeSb 2 O 4 a ete etudie entre 4, 7 et 800°K par effet Mossbauer. On a observe une temperature de Neel T N = 46 ± 1°K; les spectres obtenus a basse temperature permettent d'eliminer l'une des deux structures magnetiques proposees par Gonzalo-Cox-Shirane 1 et de preciser la direction des spins par rapport aux cotes de la maille; l'evolution du couplage quadrupolaire en fonction de la temperature montre que les deux niveaux orbitaux excites les plus proches sont situes respectivement a 300 et 900 cm −1 du niveau fondamental.

We discuss here the results and the interpretation in the crystalline-field approach of some Mossbauer experiments on Fe2+ ions in the spinels GeFe2O4, GeCo2O4 and GeNi2O4. Once the sign of the quadrupolar interaction e2qQ has been deduced from a magnetic spectrum, the thermal variation of e2qQ may be used for determining the electronic level scheme of the Fe2+ ion (including the energies and wavefunctions of the levels). Then we may predict the form and magnitude of the spin hamiltonian, of the magnetic anisotropy and of the hypefine field tensor. Below TN the experimental results are expressed in terms of a molecular-field, the eventual variations of which have been studied in magnitude and in orientation; by using the same calculation for the three compounds, we obtained a reasonable agreement between the experimental and calculated values of the hyperfine field at 0°K.

With Au -Yb dilute alloys we report the first observation of Mossbauer relaxation spectra of a rare earth ion submitted to an isotropic hyperfine interaction. We derive the relaxation rate by applying the stochastic model of Clauser and Blume which we have found to be equivalent in this particular case to the perturbation theory of Hirst; the corresponding value of the exchange constant Jsf is compatible with a recent EPR measurement.

We discuss here the results and interpretation of some Mossbauer experiments on FeCr2O4, FeV2O4, and GeFe2O4. A detailed study of the thermal variation of the spectra leads to a determination of both quadrupolar coupling and hyperfine field at the 57Fe nucleus as a function of temperature. Knowing the local symmetry around the Fe2+ ion, which is tetragonal in the first two cases, and trigonal in the last one, it is possible to deduce from the quadrupolar coupling the form of the lowest orbital wavefunction of the Fe2+ ion. In FeCr2O4 and FeV2O4, this may be combined with the optical data obtained by Slack on the very similar compound FeAl2O4, to predict the form and magnitude of the spin Hamiltonian and magnetic anisotropy, as well as that of the hyperfine field tensor (using a reasonable estimate for the core hyperfine field). In GeFe2O4 similar predictions can be made after deducing the distance to the first excited orbital level from the thermal variation of e2qQ. The interest of such calculations in c...

On obtient par irradiation aux neutrons du dodecaborure de thulium une source Mossbauer pour 170Yb a raie unique et fine, ayant un facteur de Debye-Waller considerable (fo ≈ 34%). L'hexaborure d'ytterbium possede un facteur fo beaucoup plus faible (fo≈10%) et un deplacement isomerique caracteristique de la valence 2+. A narrow single line Mossbauer source for 170Yb, with alarge Debye-Waller factor (fo≈34%), is obtained by neutron irradiation of thulium dodecaboride. Ytterbium hexaboride exhibits a much lower fo factor (fo≈10%) with an isomer shift characteristic of the 2+ oxidation state.

Resume Les spectres Mossbauer observes au-dessus et au-dessous de la temperature de Neel ne sont pas affectes par des phenomenes de relaxation lente et permettent une determination precise des parametres hyperfins. L'interpretation confirme les resultats d'autres etudes sur les proprietes electroniques des ions Yb 3+ dans ces composes et fournit notamment une evaluation plus precise de leurs moments magnetiques.

Detailed Mossbauer measurements at low temperatures on the dilute alloy Au -Yb show the first experimental evidence of a Kondo type logarithmic contribution to the relaxation rate of the localized moment.