Mossbauer spectroscopy uranium

The ions in the tetrahedral sites have been shown by Mossbauer spectroscopy to have an oxidation state of +3. In a way similar to the uranium oxide structure, the distance between the closest octahedral holes and the tetrahedral hole is too short to allow both sites to be occupied simultaneously. In this case, four vacancies on the octahedral sites are created for every interstitial tetrahedral ion, as shown in Figure 6.8. This type of cluster occurs at low values of x. As x increases, larger clusters form in which there are thirteen vacancies and four interstitial ions. This is called a Koch-Cohen cluster (Figure 6.9). 

STUDY OF EXOTIC URANIUM COMPOUNDS USING MOSSBAUER SPECTROSCOPY... 

Mossbauer spectroscopy is in reality the only tool to investigate the hyperfine interactions at the uranium site in such exotic uranium intermetallics. There are several uranium isotopes such as U, and U. The natural abundances of these isotopes are 0.005,0.72, and 99.27%, respectively. The ground state of the nuclei iszeroin U and due to which it is impossible to carryout NMR experiments. Although the isotope whose nuclear ground state... 

Background of Mossbauer Spectroscopy and Its Application to Magnetism in Uranium Compounds... 

Some uranium magnetic compounds were measured by Mossbauer spectroscopy. The hyperfine fields in these compounds were determined by Mossbauer spectroscopy [6,7,9,11]. In most of the uranium compounds, the relationships between the hyperfine field and ordered magnetic moment obey a linear correlation as shown in Fig. 7.5. The hyperfine coupling constant of the uranium compounds is about l50T//i,B. 

Summary of Mossbauer Spectroscopy of Uranium-Based Heavy Fermion Superconductors... 

In Mossbauer spectroscopy, isomer shift, which is one of the important parameters to discuss the hybridization between 5f eiectrons at uranium atoms and electrons at the other atoms, is difficult to observe as mentioned above. However, hyperfine coupling constant at nuclei is a complementary parameter to discuss the hybridization at the uranium site. Typical coupling constants in uranium-based intermetallics are about I50T//xb, to our best knowledge. When coupling constants smaller than 150 TZ/ b te obtained in some compounds, it can be concluded that the nature of the 5f electrons in them is more delocalized than that in typical uranium-based intermetallics because of the expansion of the wave functions of 5f electrons. 

Plots of the hyperfine coupling constant at uranium nuclei by Mossbauer spectroscopy and the cyclotron masses obtained by de Haas-van Alphen effect measurements in the series of uranium dipnictides. 

Hyperfine interactions at U nuclei in uranium dipnictides are correlated with the magnetic sequence in their antiferromagnetic states. Because of high Neel temperature, the lattice contribution in the EFG tensor is difficult to estimate. Therefore, it has not been clarified experimentally whether the nuclear quadrupole interaction is caused by the cancellation between the 5f quadrupole moments and lattice contributions or not Considering the crystal structure of the series of the uranium dipnictides, the pnictogen dependence of the lattice contribution in the EFG tensor is small. The results ofthe U Mossbauer spectroscopy imply that the electronic structure thataffects the hyperfine interactions at nuclei... 

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