Temperature induced valence phase transition in intermediate-valent YbPd₂Al₃

Abstract

A temperature induced valence phase transition from Yb3+ at higher temperatures to Yb2+ at lower temperatures was observed at T = 110(1) K for intermetallic YbPd2Al3.

Extending the knowledge on the quaternary rare earth nickel aluminum germanides of the RENiAl4Ge2 series (RE=Y, Sm, Gd–Tm, Lu) – structural, magnetic and NMR-spectroscopic investigations

“…Likewise for LuNi-Al 4 Ge 2 the s-DOS is 0.0156 states per eV for an Al1 atom at E F and therefore higher as for an Al2 atom, for which the partial DOS with s character is only 0.0123 states per eV at E F . These differences in the s-DOS at E F reflects the difference of the isotropic magnetic de-shielding contributions, δ iso ms , observed in the solid-state 27 Al MAS-NMR measurements.…”

“…The saturation magnetization is μ sat = 6.61(1) μ B (3 K, 80 kOe), the expected saturation is 9 μ B according to g J × J. Figure 8 shows the solid-state 27 Al MAS-NMR spectra of the central transition region for YNiAl 4 Ge 2 and LuNiAl 4 Ge 2 measured at B 0 = 14.1 T. For both compounds, two distinct resonances are observed in an approximate 1:1 ratio, confirming the presence of two crystallographically distinct aluminum sites in the crystal structures. To extract the relevant interaction parameters for these species, one would normally simulate the corresponding line-shapes on the basis of second-order quadrupolar perturbations, using e.g.…”

“…All samples were investigated in the temperature range of 2.5-300 K with applied external magnetic fields of up to 80 kOe (1 kOe = 7.96 × 10 4 A m −1 ). 27 Al solid-state NMR spectra of YNiAl 4 Ge 2 and LuNiAl 4 Ge 2 were recorded with a Bruker Avance Neo (B 0 = 14.1 T) and an Agilent DD2 (B 0 = 5.7 T) NMR spectrometer using magic-angle spinning rates between 37 and 40 kHz. To reduce the electrical conductivity and density, the finely powdered samples were mixed in approximate volume ratios of 1:2 with dry potassium bromide and filled into a conventional ZrO 2 MAS rotor with 1.3 or 1.6 mm diameter.…”

“…MAu 2 Al 2 with M = Ca, Sr [20]; MAuX with M = Ca-Ba and X = Al-In [21]; MPtAl 2 with M = Ca-Ba [22]) and the rare earth elements (e.g. RET 5 Al 2 with RE = Y, Gd-Tm, Lu and T = Pd, Pt [23], RE 2 TAl 3 with RE = Y, La-Nd, Sm, Gd-Lu and T = Ru, Rh, Ir [24], Eu 2 Pt 6 Al 15 [25], Eu 2 Ir 3 Al 9 [26] or YbPd 2 Al 3 [27]), the interest of extending the knowledge of quaternary aluminum containing compounds has sparked. Amongst the vast number of potential elemental combinations, the aluminum germanides of the rare earth elements were chosen due to the pronounced differences in the electron count of the respective elements, enabling single-crystal X-ray diffraction experiments.…”

“…However, no ordered binary aluminum germanides are known. Here we report on the synthesis and the structural, magnetic, 27 Al NMR spectroscopic and theoretical (DFT level) characterization of several new members of the RENiAl 4 Ge 2 series (RE = Y, Sm, Gd-Tm, Lu).…”