Introduction of Uranium Dipnictides

Orbital degrees of freedom are one of the important parameters to discuss the ordered ground states in materials. Orbital occupancy reflects electric field gradient (EFG) at nuclei. Then, Mossbauer spectroscopy can detect orbital occupancy of electrons, especially d or f electron cases. Electronic orbits in f electrons are usually called electronic quadrupole moments. Electronic quadrupole moments directly interact with nuclear quadrupole moments, which are observed as nuclear quadrupole interactions. Since the nuclear quadrupole moment in the Mossbauer transition is relatively large, 3.1 barn, the nuclear quadrupole interaction is relatively easy to detect as asymmetry of spectra even when hyperfine fields are observed. 

TABLE 7.3 Characteristic Physical Properties in Uranium Dipnictides [63,66]  

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. 

2 Hyperfine Interactions Correlated with the Magnetic Structures in Uranium Dipnictides 

7 STUDY OF EXOTIC URANIUM COMPOUNDS USING U MOSSBAUER SPECTROSCOPY 

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