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|Type:||Artigo de periódico|
|Title:||Spin structure and first-order transition of GdIn(3): Near-surface magnetism, buried amplitude-modulated phase, and interface delocalization|
|Abstract:||A resonant x-ray magnetic diffraction study was performed for pure and (Cd,Ga)-doped GdIn(3) single crystals with cubic structure. All studied samples show an equal-magnitude antiferromagnetic spin structure with propagation vector (tau) over right arrow=[1/2, 1/2,0] at low temperatures, corresponding to a parallel spin propagation along the (c) over right arrow direction (normal to the studied surfaces) and antiparallel propagation along (a) over right arrow and (b) over right arrow. A complex magnetic behavior in the submicrometric near-surface region (NSR) was found close to T(N)(bulk) similar to 44 K. For both pure and substituted samples, a fairly strong signal from the equal-magnitude magnetic phase was found to survive above T(N)(bulk) and abruptly disappears at T(N)(NSR) similar to T(N)(bulk)+ 0.7 K, indicating that the NSR may show a larger T(N) than the bulk for all studied samples. For the pure compound only, satellite peaks consistent with an amplitude-modulated magnetic phase with a wavelength of 380 angstrom were found between T(N)(bulk) and T(N)(NSR). A successful fit of the scattering profile around several magnetic Bragg positions and photon energies, using a simple phase coexistence model, confirmed that the amplitude-modulated phase develops underneath the most superficial region showing the equal magnitude structure. The evolution of the magnetic scattering profile on cooling indicates that the interface between equal-magnitude and amplitude-modulated phases diverges towards the bulk as T -> T(N)(bulk) from above. A detailed analysis of the magnetic scattering, as well as the existence of a single bulk transition within the experimental sensitivity of our specific heat and magnetic susceptibility measurements, in contrast to the rich behavior shown by the near-surface region, indicates that the amplitude-modulated phase is not bulk representative, being actually sandwiched between the bulk paramagnetic and the equal-magnitude phases. Depth-temperature phase diagrams for pure and (Ga,Cd)-doped GdIn(3) are drawn on the basis of our results, which are discussed in terms of a three-phase coexistence scenario theoretically proposed for first-order transitions in the NSR.|
|Editor:||Amer Physical Soc|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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