5f magnetism

Fig. 3.12. Magnetic amplitude Mu/(2) for uranium in UNi2 measured by polarized neutron diffraction, with f(Q) is the form factor [/(0) = 1] and is the 5f magnetic moment. The solid curve represents the calculated magnetic amplitude (Fournier et al. 1986).

We hope to have demonstrated to the readers that pSR has developed into a major tool for microscopic studies of magnetism and that its application to 4f- and 5f-magnetic materials is broad and mifitifaceted. In fact, the amount of data revealed by our literature search surprised us. This is even more astonishing when considering that we have not discussed... 

Fig. 4.5 Comparison of Al" ion images from an Al on Si contact pattern with operation in the ion microprobe left) and ion microscope right) modes in a Cameca IMS 5f magnetic sector instrument (5.5 keV O2 primary beam)...

As the actinides are a Second f series it is natural to expect similarities with the lanthanides in their magnetic and spectroscopic properties. However, while previous treatments of the lanthanides (p. 1242) provide a useful starting point in discussing the actinides, important differences are to be noted. Spin-orbit coupling is again strong (2000-4000 cm ) but, because of the greater exposure of the 5f... 

Fournier JM, (1985) Actinide Solids. 5f Dependence of Physical Properties. 59160 1-56 Fournier JM, Manes L (1985) Magnetic Properties of Actinide Solids. 59160 127-196 Fraga S, Valdemoro C (1968) Quantum Chemical Studies on the Submolecular Structure of the Nucleic Acids. 4 1-62 Frasinski LJ, see Codling K (1996) 85 1-26... 

Apart from d- and 4f-based magnetic systems, the physical properties of actinides can be classified to be intermediate between the lanthanides and d-electron metals. 5f-electron states form bands whose width lies in between those of d- and 4f-electron states. On the other hand, the spin-orbit interaction increases as a function of atomic number and is the largest for actinides. Therefore, one can see direct similarity between the light actinides, up to plutonium, and the transition metals on one side, and the heavy actinides and 4f elements on the other side. In general, the presence or absence of magnetic order in actinides depends on the shortest distance between 5f atoms (Hill limit). 

In this paper, we report MCP of Use and UTe which have been carried out at AR-NE1 station of KEK, Japan, and try to separate the spin and orbital contributions of magnetic moments by combining MCP with the magnetization measurement. Furthermore, we discuss the degree of localization of 5f electrons of these samples by decomposing the MCP into localized component and itinerant component. 

The spin moments were decomposed into localized 5f component, ps(5f), and diffused components, ps(diff). Combining magnetization measurement with this decomposition, the orbital contribution, pL(5f), has been deduced. ... 

The increase of the total magnetic moment from USe to UTe is the result of the decrease of spin moment from 5f electrons due to the stronger hybridization effects between U atom and Te atom. 

A larger number of examples of 5f- 3d systems are known, and have been recently reviewed [43]. We reiterate here only the potentially enormously beneficial effect of sizable 5f-3d exchange couplings exploiting the large magnetic moments of first row transition metal ions and the anisotropy of actinides. Examples are the previously discussed U-Mn wheel and chain [36, 38]. 

Its constant paramagnetism is well explained by a Van Vleck susceptibility, the ground state being the non-magnetic J = 0 due to the 5f configuration this interpretation is well confirmed by the very low electronic specific heat. Accordingly, band calcula-... 

It can be stated that up to plutonium, 5 f electrons are in the conduction band and have no magnetic moment from americium on, 5f electrons are localized and carry a magnetic moment. 

The physical properties of actinide metals up to Pu - including the magnetic properties-are all governed by the complicated 5f-6d-7s conduction band. 

No Hill plots can be drawn for transplutonium compounds for obvious reasons very few are known, Am compounds are essentially non-magnetic (J = 0) and all known results suggest well localized 5f states. 

From Fig. 8, one notices that the localized enthalpy is lower by about 0.9 eV than the itinerant one, thus classifying americimn metal among the lanthanide-like, heavier actinides. The picture is consistent with the results of magnetic measurements, which explain magnetism in americium metal as derived from a 5f, J s 0 atomic ground state. 

The most important factor governing the physical, and in particular magnetic, properties of the actinides, is the extended nature of the 5f wave functions. Depending on ... 

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