Intermetallic compounds magnetic susceptibility

Many models have been postulated to account for the interconfiguration fluctuations (ICF) in rare earth intermetallic compounds. We will consider Hirst s model which assumes that the 4/ electrons are highly correlated and preserve their atomic-like features during the valence fluctuation. Both the X-ray photoelectron spectra and the magnetic susceptibility of rare earth intermetallic compounds can be successfully explained on the basis of Hirst s model [8,11]. 

Since the X-ray diffraction studies of Zintl et al. , these members of the family of intermetallic compounds have been of special interest because some of their chemical properties are unusual for intermetallic phases. Many experimental investigations have been reported for binary and ternary B32 type compounds. Besides the crystal structure " , the thermodynamic behavior , electrical conductivity ", magnetic susceptibility , NMR data elastic constants - and optical properties have been studied. Additionally for LiAl electrochemical investigations have been performed in view of the recent interest in fast ionic conductors " . ... 

Much attention was paid to slruelures, superconducting properties, magnetic susceptibilities, Knight shifts, and specific heats of intermetallic compounds of technetium. Their structure types and lattice constants arc presented in Table 9.3. A. 

A study of the Yb-Al system reveals that the only intermetallic compounds formed are YbAlg (melting congruently at 1360 °C) and YbAlg (formed peritectically at 980 °C). Magnetic susceptibilities and lattice constants were determined for these phases in the temperature range —180 to -1-550 °C. 

In the present section we focus on the various chemical and physical properties of the equiatomic YbTX compounds especially the physical properties, which have been intensively investigated in the last two decades. Besides detailed magnetic susceptibility and electrical resistivity measurements, various other techniques have been used to get deeper insight into the peculiar properties of these intermetallics " Sn and °Yb Mdssbauer spectroscopy, specific-heat data, thermopower measurements, solid-state NMR, photoemission studies, neutron dif action, muon spin relaxation, and a variety of high-pressure experiments. The diverse data are summarized in the following subsections. 

Pronounced crystal-field effects were observed in the paramagnetic phase NMR for intermetallic compounds of Ce, Pr, Sm or Tm. Crystal-field effects for Tm in TmAlj have been analysed by de Wijn et al. (1970) by a combination of the temperature dependences of the Al Knight shift and of the magnetic susceptibility. These authors also analysed the quadrupole interaction for the Al site in the cubic CujAu structure. Comparing the experimental value e qQ/h = 7.6 MHz with the point-charge model value (Abragam 1961)... 

Seipler, D., 1975, On the local susceptibilities of the conduction electrons and their exchange interaction with Gd in dilute intermetallic compounds, in Proc. XIXth Congr. AMPERE on Magnetic Resonance and Related Phenomena, eds H. Brunner, K.H. Hausser and D. Schweitzer (Groupment Ampere, Heidelberg) pp. 297-300. 

A surface segregation model (Schlapbach et al, 1980) based on the analysis of surface properties by means of photoelectron spectroscopy and magnetic susceptibility measurements, very successfully explains the great reactivity of hydride-forming intermetallic compounds AB (e.g, LaNi ). Selective oxidation and lower surface energy of the electropositive component A (La) induces a surface segregation (Fig.12). 

In this section we describe how the specific heat, magnetic susceptibility and electrical resistivity of anomalous lanthanide and actinide intermetallics respond to applied pressure. Generally each subsection is organized by material type first Ce-based compounds, then those based on Yb and finally U-based systems. Only in the last subsection on semiconductors are these systematics broken. Although on occasions we digress into a brief discussion of the experimental observations, ihe bulk of critical discussion related to data presented here and in sect. 3 is reserved for sect. 4. 

The intermetallic compound FeAl exists with the CsCl structure (bcc). Ordered, stoichiometric as possible, FeAl exhibits a very small susceptibility, does not exhibit magnetic order, and Mossbauer studies on annealed FeAl have shown that no magnetic moment is associated with the iron atoms. When some of the A1 atoms are replaced by Fe atoms, so that Fe atoms now have Fe NN, local moments on Fe atoms with Fe NN develop. Crushing or plastic deformation also produces FeNN (see Section 1.5.2). The experiments with nonstoichio-metric FeAl indicate that Fe atoms with eight Fe NN have a moment of 1 )Ub and at low temperature, Fei 1AI0.9 orders ferromagnetically. 

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