Intermediate valence, magnetic ordering, and volume effect in the cerium-palladium system

Crystal Structure and Magnetic Susceptibility of Ce8Pd24Sb

“…The Cu3Au unit found at the centre of the unit cell (Fig. 2b) is essentially an expanded C ePd3 cell 4.207(1)A on edge (versus 4.126Ä in binary CePd3 [3]), which is comparable to what Kappler et al [3] refer to as "magnetic C ePd3". It is evident from Fig.…”

“…The C e-P d(l) and Ce-Pd(3) distances are both com parable to the Ce-Pd distance in CePd3 (2.97Ä) while the Ce-Pd(2) distance is some 2.5% larger due to the displacement of Pd (2) from the face of the perovskite sub-cell. The Ce-Ce distance is also larger, being 4.207A between nearest ce rium atoms within the cell and 4.254A between adjacent cells which are 2 -3 % increases over that in C ePd3 (4.126A [3]). These Ce-Ce distances are com parable to the limiting cell size when B, Be, Si or Ge [3] are incorporated into the centre of a C ePd3 cell.…”

“…The Ce-Ce distance is also larger, being 4.207A between nearest ce rium atoms within the cell and 4.254A between adjacent cells which are 2 -3 % increases over that in C ePd3 (4.126A [3]). These Ce-Ce distances are com parable to the limiting cell size when B, Be, Si or Ge [3] are incorporated into the centre of a C ePd3 cell. It is also interesting to note that, while in CePd3 all Pd-Pd near-neighbour distances are 2.97Ä, in Ce8Pd24Sb, the Pd(2)-Pd(3) and Pd(3)-Pd(3) distances are significantly shortened to 2.765(1)A and 2.791Ä, respectively.…”

“…1) is of a new type, being composed of distorted perovskite and Cu3Au subcells. The large size of the Sb atom is presumed to be driving the distortion since only an expansion of the lattice has been observed when a small atom such as B occupies the body-centre interstitial site in CePd3 [3,5,6], Fig. 2a shows the distorted perovskite unit "CeSbPd3" with an ad joining distorted Cu3Au unit.…”

“…A proto typical example of an interm ediate valent material is CePd3, where a strong Kondo interaction gives rise to broad maxima in the Seebeck co-efficient, resistivity and magnetic susceptibility [3][4][5]. When small elem ents such as B [3,6] or Si [3,5] were in corporated into CePd3, in a perovskite-like fash ion, the IV state was lost with heavy fermion or magnetic ordering [7] the end result. There is no published report of the incorporation of a larger pblock elem ent into the CePd3 structure, until now.…”