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|Type:||Artigo de periódico|
|Title:||Magnetic Structure And Critical Behavior Of Gdrh In5: Resonant X-ray Diffraction And Renormalization Group Analysis|
Westfahl Jr. H.
|Abstract:||The magnetic structure and fluctuations of tetragonal GdRh In5 were studied by resonant x-ray diffraction at the Gd LII and LIII edges, followed by a renormalization group analysis for this and other related Gd-based compounds, namely Gd2 Ir In8 and Gd In3. These compounds are spin-only analogs of the isostructural Ce-based heavy-fermion superconductors. The ground state of GdRh In5 shows a commensurate antiferromagnetic spin structure with propagation vector τ = (0, 1 2, 1 2), corresponding to a parallel spin propagation along the a direction and antiparallel propagation along b and c. The spin direction lies along a. A comparison between this magnetic structure and those of other members of the Rm (Co,Rh,Ir)n In3m+2n family (R=rare earth, n=0,1; m=1,2) indicates that, in general, τ is determined by a competition between first- (J1) and second-neighbor (J2) antiferromagnetic (AFM) interactions. While a large J1 J2 ratio favors an antiparallel alignment along the three directions (the G -AFM structure), a smaller ratio favors the magnetic structure of GdRh In5 (C -AFM). In particular, it is inferred that the heavy-fermion superconductor CeRh In5 is in the frontier between these two ground states, which may explain its noncollinear spiral magnetic structure. The critical behavior of GdRh In5 close to the paramagnetic transition at TN =39 K was also studied in detail. A typical second-order transition with the ordered magnetization critical parameter β=0.35 was experimentally found, and theoretically investigated by means of a renormalization group analysis. Although the Gd 4 f7 electrons define a half-filled, spherically symmetrical shell, leading to a nearly isotropic spin system, it is argued that a significant spin anisotropy must be claimed to understand the second order of the paramagnetic transition of GdRh In5 and the related compound Gd2 Ir In8. © 2006 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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