Synthesis, structure, and magnetic properties of LaTMg and CeTMg (T = Pd, Pt, Au)

Abstract

The title compounds were prepared from the elements by reactions in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. They crystallize with the ZrNiAl-type structure, space group P6̄2m. The structures of the cerium compounds were refined from single-crystal x-ray diffraction data: a = 767.3(1) pm, c = 410.37(4) pm, wR2 = 0.0324, 521 F2-values for CePdMg; a = 755.02(7) pm, c = 413.82(4) pm, wR2 = 0.0393, 514 F2-values for CePtMg; and a = 774.1(3) pm, c = 421.6(1) pm, wR2 = 0.0355, 395 F2-values for CeAuMg, with 14 variables for each refinement. The palladium compound shows a small homogeneity range: CePd1+xMg1-x. The structures contain two crystallographically different transition metal sites T1 and T2 which are located in tri-capped trigonal prisms: [T1 Mg6Ce3] and [T2 Ce6Mg3]. Magnetic susceptibility and heat capacity measurements reveal long-range magnetic ordering at 2.1(2) K for CePdMg, 3.6(2) K for CePtMg, and 2.0(2) K for CeAuMg. Curie-Weiss behaviour at higher temperatures shows that the cerium ions are in the 3+ oxidation state. The isotypic LaTMg compounds are Pauli paramagnetic down to lowest temperatures (T = 0.3 K). All the compounds, RETMg (RE = La, Ce; T = Pd, Pt, Au) show metallic behaviour.

Rare earth–transition metal–magnesium compounds—An overview

“…In contrast to the investigation by Gibson et al [33], no magnetic ordering has been reported for CePdMg. Ce 2 Ni 2 Mg, and CeNi 4 Mg are intermediate-valent compounds.…”

“…The lanthanum and cerium based series LaTMg and CeTMg (T ¼ Pd, Pt, Au) [33] have been investigated in detail. All three lanthanum compounds show Pauli paramagnetism down to 0.3 K. Cerium is in a stable trivalent oxidation state in the CeTMg (T ¼ Pd, Pt, Au) compounds.…”

“…Complete measurements of the specific heat data are available for the series LaTMg and CeTMg (T ¼ Pd, Pt, Au) [33]. These compounds show very small values for the electronic specific heat coefficients.…”

Structure and Magnetic Properties of CePtZn

“…In the platinumbased series we were recently able to further reduce the VEC by substitution of indium by magnesium. In ZrNiAl-type CePtMg [7], magnesium takes part in the covalently bonded [PtMg] network and the magnetic ordering temperature is 3.6 K. Several systems like CeAuIn 1−x Mg x show complete solid solubility [8]. We have now started a more systematic investigation of the corresponding zinc-based systems, in order to elucidate similarities to the magnesium compounds.…”

New metal-rich compounds RE23Pt7Mg4 (RE = La, Ce, Pr, Nd, Sm)

“…In the course of our systematic phase analytical studies of ternary RE x T y Mg z compounds we have now focused on the platinum-based systems. So far only the equiatomic compounds REPtMg (RE ¼ La, Ce, Pr, Nd, Sm, Gd) [16][17][18], and the rare earth-rich compounds RE 4 PtMg (RE ¼ Y, Nd, Sm, Gd) [19] have been synthesized. Herein we report on the new series RE 23 Pt 7 Mg 4 (RE ¼ La, Ce, Pr, Nd, Sm) with Pr 23 Ir 7 Mg 4 type structure.…”