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|Type:||Artigo de periódico|
|Title:||Magnetic structure and critical behavior of GdRhIn5: Resonant x-ray diffraction and renormalization group analysis|
|Abstract:||The magnetic structure and fluctuations of tetragonal GdRhIn5 were studied by resonant x-ray diffraction at the Gd L-II and L-III edges, followed by a renormalization group analysis for this and other related Gd-based compounds, namely Gd2IrIn8 and GdIn3. These compounds are spin-only analogs of the isostructural Ce-based heavy-fermion superconductors. The ground state of GdRhIn5 shows a commensurate antiferromagnetic spin structure with propagation vector (tau) over right arrow=(0,(1)/(2),(1)/(2)), corresponding to a parallel spin propagation along the (a)over-right-arrow direction and antiparallel propagation along (b)over-right-arrow and (c)over-right-arrow. The spin direction lies along (a)over-right-arrow. A comparison between this magnetic structure and those of other members of the R-m(Co,Rh,Ir)(n)In3m+2n family (R=rare earth, n=0,1; m=1,2) indicates that, in general, (tau)over-right-arrow is determined by a competition between first- (J(1)) and second-neighbor (J(2)) antiferromagnetic (AFM) interactions. While a large J(1)/J(2) ratio favors an antiparallel alignment along the three directions (the G-AFM structure), a smaller ratio favors the magnetic structure of GdRhIn5 (C-AFM). In particular, it is inferred that the heavy-fermion superconductor CeRhIn5 is in the frontier between these two ground states, which may explain its noncollinear spiral magnetic structure. The critical behavior of GdRhIn5 close to the paramagnetic transition at T-N=39 K was also studied in detail. A typical second-order transition with the ordered magnetization critical parameter beta=0.35 was experimentally found, and theoretically investigated by means of a renormalization group analysis. Although the Gd 4f(7) 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 GdRhIn5 and the related compound Gd2IrIn8.|
|Editor:||Amer Physical Soc|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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