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|Type:||Artigo de periódico|
|Title:||Spin Structure And First-order Transition Of Gd In3: 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 Gd In3 single crystals with cubic structure. All studied samples show an equal-magnitude antiferromagnetic spin structure with propagation vector τ = [1 2, 1 2, 0] at low temperatures, corresponding to a parallel spin propagation along the c direction (normal to the studied surfaces) and antiparallel propagation along a and b. A complex magnetic behavior in the submicrometric near-surface region (NSR) was found close to TNbulk ∼44 K. For both pure and substituted samples, a fairly strong signal from the equal-magnitude magnetic phase was found to survive above TNbulk and abruptly disappears at TNNSR ∼ TNbulk +0.7 K, indicating that the NSR may show a larger TN 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 Å were found between TNbulk and TNNSR. 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→ TNbulk 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 Gd In3 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. © 2008 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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