Unit cell volume reduction of Gd5(Si,Ge)4 nanoparticles controlled by bulk compressibility

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Andrade, V. M. ; Belo, J. H. ; Checca, N. R. ; Rossi, A. ; Garcia, F. ; Almeida, B. ; Tedesco, J. C. G. ; Poulain, A. ; Pereira, A. M. ; Reis, M. S. ; Araujo, J. P.

• Tipo de documento: Artigo Científico
• Fonte: Journal of Alloys and Compounds; v. 849, p. 9-pg., 2020-12-30.

Resumo

The production of Gd-5(Si,Ge)(4) compounds in reduced dimensionality, through pulsed laser deposition (PLD), have shown their potential for practical applications. Here, we present nanoparticles ranging from 10 to 27 nm of average particle size of Gd-5(SixGe1-x)(4), with x = 0, 0.45 and 0.60, obtained using an Nd:Yag (1064 nm) and an Excimer KrF laser (248 nm). Synchrotron X-ray Diffraction measurements revealed a reduced unit cell volume in comparison to their bulk counterpart. The x = 0 sample presented a similar to 1.99% reduction while x = 0.45 composition, a shrinkage of similar to 1.81% on the unit cell volume that are a result of a structural change to a Gd5Si4-type structure [O(I)]. In contrast, x = 0.60 nanoparticles conserve the bulk crystal structure with similar to 0.95% of volume shrinkage. As a consequence, there is a change on the magnetic transition order from a first to a second one for all nanostructures followed by a magnetocaloric response reduction. These observations unveil a direct correlation between the bulk compressibility values and the unit cell shrinkage, suggesting that the rise of a surface stress plays a major role on the particle and unit cell dimensions. (C) 2020 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 17/10581-1 - Fenômenos emergentes em sistemas de dimensões reduzidas
• Beneficiário: Pascoal Jose Giglio Pagliuso
• Modalidade de apoio: Auxílio à Pesquisa - Projetos Especiais