Possible heavy-fermion behavior and field-induced transitions in new R-Pt-Ga compounds

Abstract

We have discovered a new family of rare earth compounds that we identify as Rz-xPt4Ga8 + y. Single crystals of this family have been grown for R-=La, Ce, Pr, Nd, Sm, Gd, Er, Yb and Y. Many members (cerium, praseodymium, neodymium, samarium and erbium) show large anisotropies in their magnetic susceptibility; further, electrical resistance, magnetic susceptibility and specific heat measurements on the cerium member indicate that it is very possibly a heavy-electron compound with an electronic specific heat T= 1 J K -2 mol -~. Additionally, other members of the family have a magnetic transition at low temperatures. The electrical resistance, magnetic susceptibility and specific heat in fields will be presented for the praseodymium-based compound in which there is a field-induced transition.

Structure of Ce2Pt6Ga15: interplanar disorder from the Ce2Ga3 layers

“…Earlier rough estimates of the rare-earth concentration from susceptibility data for RE2Pt6Gal5 compounds show that it is reasonably constant in these materials, ranging from 1.91 for RE -Nd to 2.21 for RECe (Lacerda et al, 1992). The site occupancy for Ce from our studies is consistent with these values, giving more accurate values of the overall Ce concentration that range from 1.89 to 2.07.…”

“…Clearly, a better understanding of the properties of these materials requires a better knowledge of the structure and an understanding of the nature of the possible disorder. An earlier single-crystal X-ray determination of the structure of Ce2Pt6Gals, referred to as Ce2 _ xPt4Gas +, in earlier work (Lacerda et al, 1992), suggested that the structure conformed to a primitive-hexagonal space group, but a Fourier map suggested a Ga site too close to the Ce site . The absorption corrections © 1996 International Union of Crystallography Printed in Great Britain -all rights reserved in these X-ray data were very large and, as a result, the correctness of the structure remained unconfirmed.…”

“…The absorption corrections © 1996 International Union of Crystallography Printed in Great Britain -all rights reserved in these X-ray data were very large and, as a result, the correctness of the structure remained unconfirmed. In the subsequent article (Lacerda et al, 1992) we presented the results of preliminary structural refinements in the space group P31c using powder neutron diffraction data that suggested the earlier structure to be basically correct, but with both Ce and Ga sites partially occupied, most likely with vacancies correlated to avoid close Ce and Ga encounters. One of the issues raised in this work was the degree of correlation of the vacancies and if a larger ordered cell would provide a better description.…”

“…This family of compounds exhibits extremely interesting, but still poorly understood, magnetic and transport properties (Lacerda et al, 1992). The poor resistance ratio [R(300 K)/R(2 K)] of the order unity suggests that the crystals may be disordered.…”

Ternary compounds Ce0.67Pt2Al5 and Ce1.33Pt3Al8

“…[1]. The crystal structure was determined for one of the representatives of this family, namely Ce 2−x Pt 4 Ga 8+y (a = 4.313Å and c = 16.516Å, space group P31c).…”