S. Ofer

Observation of the Goldanskii effect over a wide temperature range

Abstract The Goldanskii effect was observed in the recoilless absorption spectra of the 21.6 KeV gamma ray of 151 Eu in Eu 2 Ti 2 O 7 between 4 and 900 K. Full agreement between the Goldanskii theory and the experimental spectra was obtained throughout the whole temperature range.

Mössbauer-effect studies of excited states of 155Gd, 156Gd and 157Gd

Abstract Mossbauer-effect studies yield the following nuclear parameters: In 155Gd, Q(86)/Q(0) = 0.087 ± 0.006, Q(105)/Q(0) = 1.00 ± 0.03. In 156 Gd , g(89) = 0.386 ± 0.004, 156 Q(89)/ 155 Q(0) = −1.51 ± 0.02. In 157 Gd , Q(64)/Q(0) = 1.80 ± 0.03 and g(64) = −0.185 ± 0.005 . The value of g(89) is in very good agreement with the theoretical value.

Dependence of interconfiguration excitation energies on local environment, composition and temperature in EuA2−xBx compounds

Abstract The dependence of the energy released by removing an electron from the 4ƒ level to the conduction band on environment, composition and temperature was deduced from Mossbauer measurements on Eu A 2- x B x compounds ( A = Rh or Ir, B = Pt or Al). For each system, this energy is equal to α + β x - λ m + T , where α, β and λ are constants. m is the number of B neighbors of an Eu ion. The sizes of the unit cells are consistent with the recoilless absorption data.

Mössbauer effect studies of cubic237NpM3 intermetallic compounds

Abstract The Mossbauer effect in 237Np has been used to investigate the hyperfine interactions in NpPd3, NpGe3 and NpRh3. NpPd3 has a first order magnetic transition at 49K and NpSn3 orders magnetically at 9K. The saturation hyperfine fields in NpPd3 and NpSn3 are 3.35 MOe and 0.55 MOe, respectively. NpGe3 and NpRh3 do not order magnetically even at 1.7K. The isomer shifts of the NpM3 compounds change regularly with the size of the (AuCu3 type) unit cell.

Mossbauer studies of after alpha decay effects of Np237 in delta plutonium

Abstract Mossbauer studies of the 59.6 keV gamma ray emitted from Np 237 in δ-Pu show that the shape and the center of gravity of the emission spectrum change significantly with temperature between 8 and 80 K. The results can be very well explained by assuming that the Np 5+ ions produced after the alpha-decay of 241 Am transform with a rate of ∼ 10 8 sec −1 to the Np 4+ valence state.

Quadrupole interactions and relaxation effects in Dy2Ti2O7

Abstract Studies of quadrupole interactions and relaxation phenomena in Dy 2 Ti 2 O 7 at various temperatures up to 750 K have been performed using the Mossbauer effect of the 25.6 keV transition in 161 Dy. The source used was 161 Tb in 160 Gd 2 Ti 2 O 7 at 150 K, which emits a very narrow 25.6 keV γ line. Quadrupole interaction parameters and relaxation times, as function of temperature, were deduced from the measurements.

Crystalline fields, exchange interactions and spin reorientations in TmxHo1−xFe2 systems, studied by a Yb170 Mössbauer probe☆

Abstract Mossbauer studies of the 84.3 keV gamma ray of Yb 170 emitted from Yb in Tm x Ho 1− x Fe 2 at various temperatures were performed. These yield the crystalline field parameters ( A 4 〈 r 4 〉 = 36 ± 5 K, A 6 〈 r 6 〉 = -3 ± 2K, the exchange field ( μ B H exch = 116 ± 4 K) and the Yb 3+ free ion hyperfine constants ( H 4 f = 4100 ± 150 kOe, eqQ = 2400 ± 250 MHz and H (conduction electrons) = 350±100 kOe). Spin relaxation phenomena observed in TmFe 2 at low temperatures give a value of ∼ 0.03 for | ϱ ( E F ) J sf |. Spectra observed in Tm 0.2 Ho 0.8 Fe 2 in the spin reorientation transition region indicate that the transition is of second order.

Temperature dependence of the magnetic fields acting on dilute tin nuclei and on their closest magnetic neighbours in yttrium iron garnet

Abstract The temperature dependence of the hyperfine field acting on dilute Sn 119 in yttrium iron garnet (YIG) has been measured by the Mossbauer effect technique. The results were analysed in terms of the magnetic behaviour of the iron ions close to the tin impurity. A simple parameterless molecular field calculation reproduces the experimental observations perfectly.

NGR STUDY OF DYSPROSIUM DIHYDRIDE AT LOW TEMPERATURES.

Abstract From a Mossbauer study of DyH 2 ( T N ∼ 8 K) at low temperatures we conclude that even at 0.23 K two Dy 3 + ionic levels are populated. The magnetic moments of the two levels, the splitting between them and relaxation times are estimated from the experimental results using a simple model.

Rare earth contribution to the hyperfine field acting on 119Sn in rare earth iron garnets

Abstract The rare earth contribution (−27 ± 2 koe in GdIG) to the hyperfine field acting on 119Sn in iron garnets has been found to be a monotonic, but not a linear function of the experimental value of the rare earth ionic spin. This non-linearity is due to an anisotropic transfer mechanism. The ratio of gex/go in 119Sn was found to be −0.2154 ± 0.0002.