New orthorhombic modification of equiatomic CePdAl

Abstract

The crystal structure of a new low-temperature modification of CePdAl was determined from single-crystal x-ray data: CePdAl-type; space group Pmmn (No. 59), Z = 14, oP42, a = 0.426 07 nm, b = 2.887 58 nm, c = 0.721 90 nm; R F = 0.048. Physical properties of orthorhombic CePdAl are governed by a mutual balance of the RKKY interaction, the Kondo effect and crystalline electric field splitting, resulting in antiferromagnetic ordering below ≈2.5 K. Electronic transport is reminiscent of a textbook-like Kondo lattice, which comes along with a significant negative magnetoresistance of more than 50% at low temperatures. Although geometrical frustration is absent when compared to the hexagonal modification of CePdAl, the ordering temperature T N is even smaller. A possible cause is enhanced Kondo interactions.

Gradual Cerium Valence Change in the Solid Solution CeRu1–xPdxAl (x = 0.1–0.9)

“…Compared to CeRu 1– x Ni x Al ( x = 0.1–0.8) the structure type persists a little further over the full range from x = 0.1–0.9. This might be due to the fact that CePdAl is reported to crystallize in a second orthorhombic modification with its own structure type (CePdAl, Pmmn , a = 426.1, b = 2887.6, c = 721.9 pm21). This modification of CePdAl shows a significant structural relationship to the LaNiAl type structure and can be explained as a combination of structural elements of LaNiAl, which get separated by ZrNiAl type fragments (Figure 1, bottom).…”

“…CeRuAl exhibits intermediate valence behavior without any magnetic ordering down to 2 K,4 whereas β‐CePdAl (ZrNiAl type) shows an antiferromagnetic phase transition at T N = 2.7 K 22,23. Within its own type structure α‐CePdAl orders antiferromagnetically at even lower temperatures ( T N < 2.5 K) 21. In contrast to the reported two CePdAl phases no magnetic ordering down to 2.5 K could be observed even in low‐field studies for all investigated samples of the reported solid solution.…”

Crystal structures of isotypic aluminides CeRuAl and CeRhAl

“…The next chemical element following Rh in the periodic table, palladium, also forms an equiatomic ternary compound when reacting with Ce and Al-CePdAl. This compound crystallizes in two polymorphic modifications: high-temperature hexagonal [11] and low-temperature orthorhombic crystal structures [12]. CeRuAl and CeRhAl are closely related to the high-temperature hexagonal modification of CePdAl [11] (ZrNiAl type, space group P-62m (No.…”

Evolution of quantum criticality in CeNi9−xCuxGe4

“…To obtain a more reliable estimate for the trend of the Kondo energies in CeNi 9−x Cu x Ge 4 we utilized the resonant-level model by Schotte and Schotte [28] in combination with a molecular field approach to account for long-range magnetic order [29,30].…”