Over the past decade, nanomaterials have attracted enormous interest [1]. Their fundamental characteristic is a very small size, typically in the range of 1–100 nanometers (nm). At the nanoscale, variations in material properties are expected, leading to behavior that differs from that of bulk materials.
In bulk materials, only a relatively small percentage of atoms are located near a surface or interface (such as a grain boundary). In nanomaterials, by contrast, the surface-to-volume ratio is significantly larger. For example, for particles on the order of 10 nm, approximately 30% of the atoms are located at the surface.
In the field of rare earths (RE), unlike transition metals, studies on size effects in physical properties are relatively scarce, and the results derived from such studies may open up novel application areas, such as spintronics.
In the case of compounds based on Ce, Yb, and U, their behavior differs from that of other rare earths, exhibiting phenomena such as the Kondo effect, intermediate valence, heavy fermion behavior, non-Fermi-liquid behavior, etc. Their physical properties can hardly be explained within a free-electron framework (such as a Fermi gas) and instead fall into the category of strongly correlated electron systems (SCES). The study of size/scale effects in SCES and rare-earth systems constitutes a vast research field that has been addressed by only a very limited number of research groups.
Relevant references:
- Reduction of the Yb valence in YbAl3 nanoparticles, D.P Rojas, J.I Espeso, L. Fernández-Barquín, J. Rodríguez Fernández and J.Chaboy, Phys. Review B 78, 094412-1 a 094412-8 (2008).
- First order ferromagnetic transition in binary CeIn2, D.P Rojas, J.I Espeso, J. Rodríguez Fernández and J.C Gomez Sal, Phys. Review B 80, 184413-1_ a 184413-6 (2009).
- Phonon softening on the specific heat of nanocrystalline metals, D. P. Rojas, L. Fernández Barquín, J. Rodríguez Fernández and J. González, Nanotechnology 21, 445702 (2010).
- First-order nature of the ferromagnetism in CeIn2 investigated using muon spin rotation and by systematic substitution of La for Ce, D. P. Rojas, J. I. Espeso, J. Rodríguez Fernández, J. C. Gómez Sal, A. Andeica, C. Rusu, R. Dudric and A. Amato, Phys. Review B 84, 024403 (2011).
- Breakdown of the coherence effects and Fermi liquid behavior in YbAl3 nanoparticles, C Echevarria-Bonet, D P Rojas, J I Espeso, J Rodríguez Fernández, L Rodríguez Fernández, E Bauer, S.Burdin, S G Magalhães and L Fernández Barquín, J. Phys.: Condens. Matter 3, 135604 (2018).
- Heat capacity of nanocrystalline Yb2O3, D.P. Rojas, J.I. Espeso b, L. Rodríguez Fernández , L. Fernández Barquín, Ceramics International,48, Issue 1, 879-886 (2022).
DEFE Researcher: Daniel Rojas