Rare-earth monopnictides

In this section we present experimental results on the temperature dependence of elastic constants for intermetallic rare-earth compounds in which magnetoelastic effects due to the presence of crystal fields are dominant. There are systematic studies of these effects for given structures across the rare-earth series. Examples are the rare-earth monopnictides, especially the rare-earth antimonides (RSb), the rare-earth dialuminides (RAlj) and rare-earth compounds with the CsCl structure. From such experiments one obtains the single-ion magnetoelastic coupling constants gj. across the series and in a few cases the quadrupolar coupling constant gf [eq. (38)] too. The case of a cooperative Jahn-TeUer effect will be treated separately in sect. 2.4.3. The examples presented here can be explained mostly with the single-ion strain susceptibility Xr [ <1- (35) instead of eq. 

Rare-earth antimonides RSb. Among the rare-earth monopnictides the RSb system has been studied in greatest detail. For a discussion of physical properties of the pnictides see Hulliger (1979). 

Duan C-G, Sabirianov RF, Mei WN et al (2007) Electronic, magnetic and transport properties of rare-earth monopnictides. J Phys Cond Matt 19 315220... 

Rare earth monopnictides RX possess the NaCl type crystal structure. The primitive cell contains one molecule of RX. Figure 45 shows the crystal structure and its Brillouin zone. Especially the CeX compounds, in which X stands for N, P, As, Sb and Bi, have attracted a particular interest because of various anomalous magnetic and transport properties (Kasuya et al, 1987). LaX is expected to be a semimetal with a small and equal number of electrons and holes. A similar semimetallic character is observed in CeX, except CeN. CeX is a Kondo-lattice compound, having anomalous magnetic properties at low temperatures. Even though the carrier number is small, the Kondo effect is strong and the... 

The rare earth monopnictides are not only mutually miscible but mix also with Th, U, Np and Pu monopnictides. Vegard s law was verified in systems LnN-UN by Holleck et al. (1969). 

The rare earth monopnictides. Because of their metallic nature, their interesting magnetic properties and the simplicity of their crystal structure, the rare-earth monopnictides form a particularly interesting series of intermetallic... 

Nuclear magnetic resonance results for non-rare earth nuclei in the paramagnetic state of the cubic rare earth monopnictides. The s-f exchange parameter... 

Resume of representative recent studies of the ESR of lanthanide ions in the cubic rare-earth monopnictides. 

The transition-metal monopnictides MPn with the MnP-type structure discussed above contain strong M-M and weak Pn-Pn bonds. Compounds richer in Pn can also be examined by XPS, such as the binary skutterudites MPn , (M = Co, Rh, Ir Pn = P, As, Sb), which contain strong Pn-Pn bonds but no M-M bonds [79,80], The cubic crystal structure consists of a network of comer-sharing M-centred octa-hedra, which are tilted to form nearly square Pnn rings creating large dodecahedral voids [81]. These voids can be filled with rare-earth atoms to form ternary variants REM Pnn (RE = rare earth M = Fe, Ru, Os Pn = P, As, Sb) (Fig. 26) [81,82], the antimonides being of interest as thermoelectric materials [83]. 

O. Vogt and K. Mattenberger, Magnetic measurements on rare earth and actinide monopnictides and... 

Deformation potential coupling constants are of the order of fip, (Ziman 1960). To observe deformation potential effects in the temperature dependence of elastic constants several conditions have to be met as discussed above dpA(,(0) must be large and - Eq has to be of the order of k T. This excludes normal metals and only d-band metals with rather narrow bands can exhibit this behavior. Typical examples have been given above. In intermetallic rare-earth compounds simple density of states arguments show why elastic constant effects can be observed only for CsCl-type and Th3P4-type materials. In table 4 electronic specific heat values are listed for various rare earth compounds. This is an updated list of a previous work, see Liithi et al. (1982). This table indicates that monopnictides and monochalcogenides have smaller values of y than CsCl- and Th3P4-structure materials, i.e., the 5d band of the former structure is more hybridized than in the latter. 

MAGNETIC MEASUREMENTS ON RARE EARTH AND ACTINIDE MONOPNICTIDES AND MONOCHALCOGENIDES... 

RARE EARTH AND ACTINIDE MONOPNICTIDES AND MONOCHALCOGENIDES 313 and Tf are known. For a ferromagnet all we know is ... 

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