Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Abstract

The room-temperature crystal structure of the heavy fermion antiferromagnet Ce2RhIn8, dicerium rhodium octaindide, has been studied by a combination of high-resolution synchrotron X-ray reciprocal-space mapping of single crystals and high-resolution time-of-flight neutron powder diffraction. The structure is disordered, exhibiting a complex interplay of non-periodic, partially correlated planar defects, coexistence and segregation of polytypic phases (induced by periodic planar ;defects'), mosaicity (i.e. domain misalignment) and non-uniform strain. These effects evolve as a function of temperature in a complicated way, but they remain down to low temperatures. The room-temperature diffraction data are best represented by a complex mixture of two polytypic phases, which are affected by non-periodic, partially correlated planar defects, differ slightly in their tetragonal structures, and exhibit different mosaicities and strain values. Therefore, Ce2RhIn8 approaches the paracrystalline state, rather than the classic crystalline state and thus several of the concepts of conventional single-crystal crystallography are inapplicable. The structural results are discussed in the context of the role of disorder in the heavy-fermion state and in the interplay between superconductivity and magnetism.

Ab-Initio Reinvestigation of the (Sr-In) Binary System

“…The results are shown in Table 1. The calculated lattice parameters show a good agreement with experiments and previous calculations from literature [1], [5], [6], [17], [18]. Thus, we can rely on our atomic data set in what follows for the present work.…”

“…The crystallographic structures of the pure elements Sr and In were determined by Hirst et al [5] and Moshopoulou et al [6]. Bruzzone [2] determined also the structure of the SrIn5, SrIn3 and Sr3In, the first compound crystallize as hp6 type (P6/mmm, Cacu5), the second hp8 (P63/mmc, Mg3Cd), while the Sr3In is cubic cF16 (Fm3m, BiF3).…”

Solution growth of Ce–Pd–In single crystals: Characterization of the heavy-fermion superconductor Ce2PdIn8

“…With respect to the magnitude of the effects we exclude the influence of (completely different) impurity phase and ascribe the differences in the low-temperature behaviour to structural defects such as stacking faults typical for layered systems or small variation of composition or both. This is motivated by results on Ce 2 RhIn 8 [19] where high resolution neutron diffraction revealed Ce 2 RhIn 8 to be "a complex mixture of two layered mosaic, polytypic phases affected by non-periodic partially correlated planar defects". Also high-resolution electron microscopy may provide important data for resolving these questions.…”

“…Both the 115 and 218 compounds were mostly prepared in single crystalline form using the solution growth technique [1,4,19]. Unfortunately, in many cases the description of sample preparation is limited by citing a source where only general information about the method is presented, or even by unpublished work.…”

Cd doping effects in the heavy-fermion compoundsCe2MIn8(M=Rha

“…This behavior is consistent with the typically larger chemical disorder of the 218 materials when compared to that of the 115 materials. 30,31 The most prominent feature of the resistivity data is the evolution of T MAX , which, as shown in Fig. 4͑c͒, is increasing as a function of the Cd doping for both series.…”