Magnetic Structures of the Rare-Earth Platinum AluminidesRPtAl (R=Ce, Pr, Nd)

✍ Scribed by H. Kitazawa; A. Dönni; L. Keller; J. Tang; F. Fauth; G. Kido

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 393 KB
• Volume: 140
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1998.7881

✦ Synopsis

The rare-earth (R) platinum aluminides RPtAl crystallize in the orthorhombic TiNiSi-type structure (space group Pnma, Z‫,)4؍‬ where magnetic rare-earth atoms form a network of chains parallel to the a-axis and parallel to the b-axis. Magnetic structures and phase transitions of RPtAl (R ‫؍‬ Ce, Pr, Nd) compounds were investigated by systematic measurements of magnetic susceptibility, specific heat, and neutron diffraction on polycrystalline samples. The results reveal a large magnetocrystalline anisotropy and magnetic structures that are dominated by a ferromagnetic component parallel to one of the two chain directions: the a-axis for CePtAl and PrPtAl and the b-axis for NdPtAl. The complex magnetism of CePtAl with three successive magnetic phase transitions (T C ‫؍‬ 5.9 K, T 2 ‫؍‬ 4.3 K, T 3 ‫؍‬ 2.5 K) and two coexisting propagation vectors (k 1 ‫؍‬ 0 for T4T C , k 2i ‫؍‬ [0, 0.46, 0] for T 2 4T4T C , k 2 ‫؍‬ [0, 1/2, 0] for T4T 2 ) is confirmed to be exceptional among RPtAl compounds. PrPtAl has a nonmagnetic crystalline-electric field (CEF) ground-state singlet separated by 21 K from the firstexcited state CEF singlet and magnetic exchange interactions are strong enough to induce long-range magnetic order (Curie temperature T C ‫؍‬ 5.8 K, propagation vector k 1 ‫؍‬ 0, magnetic group Pnma, ordered saturation moment m 1 ‫؍‬ 1.00(7) B ). NdPtAl is a simple ferromagnet (T C ‫؍‬ 19.2 K, k 1 ‫؍‬ 0, Pnma, m 1 ‫؍‬ 2.08(4) B ).