Alloys lanthanides

According to this principle, the diagram of Fig. 5.10 may be considered a summary of the entire combination of trivalent intra-lanthanide diagrams. In order, indeed, to estimate the position of a special point (a critical composition, a phase boundary, etc.) in any intra-lanthanide alloy system (between the lanthanides Ln and Ln") the following rule has been proposed ... 

Figure 5.10. The generalized phase diagram, at atmospheric pressure, for trivalent (not Eu and Yb) intra-lanthanide alloys. The so-called systematization number is shown according to Gschneidner and Calderwood (1986). Notice that, in principle, the same behaviour should be expected for every mixture of any two trivalent lanthanides as long as the same (averaged) systematization number is calculated (see the text).

Among the rare-earths, samarium is the most commonly used because it provides the best permanent-magnet property. Other rare-earth elements are sometimes employed in combination with samarium to meet special requirements. The compounds SmCos and Sm2Coi7 are the most important magnetic materials among the cobalt-lanthanide alloys. 

Lanthanide alloys These alloys are used in cigarette lighter flints, magnesium alloys, and ferrous alloys. 

The Tb-light lanthanide alloys have been studied by Achiwa and Kawano (1973). They studied Tbo.8Lao.2, Tbo.sPro.2 and Tbo.75Ndo.25, all of which have the... 

It is also appropriate to mention recent experimental work on concentrated metallic lanthanide alloys and compounds which exhibit Kondo-like anomalies in their physical properties. This work indicates that lanthanide ions which behave nonmagnetically below a characteristic temperature To (as evidenced by a magnetic susceptibility which, below To, approaches a finite value as T 0) can be quite generally pictured to have a time-averaged 4f shell occupation which is nonintegral. The nonintegral 4f shell occupation (or nonintegral valence) can actually be observed by means of measurements of the lattice constant, Moss-bauer isomer shift, soft X-ray absorption and X-ray photoemission spectroscopy (XPS). 

Equation (27) refers to a valence transition of the whole lattice, i.e., every lanthanide atom in the system makes the valence change. In contrast, in the case of an f-emission (or f-addition) process by photoelectron spectroscopy (or BIS) only the valence of one lanthanide atom is changed, while the surrounding lattice remains undisturbed. As an example we first consider the photoemission process in a divalent lanthanide alloy which brings one of the 2 + ions into a 3 + state. General expressions for chemical shifts in alloys have been derived which have proven to describe the situation well (Johansson and Martensson 1980, Steiner et al. 1981). Applying these expressions to the present system we obtain for the f-ionization energy relative to the Fermi level ... 

In mixed valence materials macroscopic and microscopic measurements indicate the coexistence of two adjacent valence states of the lanthanide atom. There are two types of such solids. In one the two valence states occur on crystallographically distinguishable sites (inhomogeneously mixed valence). The main interest is in the other type, where the lanthanide atoms occupy only sites with identical point symmetry (homogeneously mixed valence). Such solids are certain intermetallic compounds and related sufficiently dilute lanthanide alloys and certain elements. 

Fig. 16.6. Two dimensional projection of probable spin alignments of amorphous lanthanide alloys (A) ferrimagnetic for Gd materials (e.g. GdFej) and (B), (C) canted ferrimagnetic for materials with lanthanide ions possessing a strong local anisotropy (e.g. TbFej) at 0 applied field (B) and finite field (C).

Direct observations of the NMR of lanthanide nuclei in the ferromagnetic state of the metals themselves or of intra-lanthanide alloys are summarized in table 18.6. Since in their ground state, all rare earth nuclei have half-integral... 

In intra lanthanide alloys, the change in Heg (i- -. the shift of the NMR frequency) is a linear function of concentration for a particular lanthanide species. This point is exemplified in the work of Sano, et al. (1975a, 1975b) and of MacKenzie et al. (1974). In the latter case, detailed investigation of the NMR of Ho in alloys with Gd, Tb, and Dy showed that the conduction electron field /f iff = /feff - /f iff could be analyzed in terms of contributions from electrons... 

Fig. 3. Generalized phase diagram for the regular lanthanides and regular intra-lanthanide alloys at low temperatures (OK), taken with slight modifictions from Kruger et al. (1990). The region covered by experiments on the regular elements is marked by thin vertical lines. The anomalous regions for the elements Ce, Eu, and Yb, as well as Pr, bid, and Sm, under higher pressures are marked by heavy vertical bars. Dashed lines represent extrapolations.

Palladium pivalate has been applied in the synthesis of Pd-based mixed-metal lanthanide alloys that may be of interest as catalysts in material science. The resulting Pd metal is bound to the lanthanide by four pivalate bridging ligands. Several of these complexes were prepared and structural properties investigated through crystallography. 

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