Atomic-scale analysis of the cation valence state distribution will help to understand intrinsic features of oxygen vacancies (V ) inside metal oxide nanocrystals, which, however, remains a great challenge. In this work, the distribution of cerium valence states across the ultrafine CeO nanocubes (NCs) perpendicular to the {100} exposed facet is investigated layer-by-layer using state-of-the-art scanning transmission electron microscopy-electron energy loss spectroscopy. The effect of size on the distribution of Ce valence states inside CeO NCs is demonstrated as the size changed from 11.8 to 5.4 nm, showing that a large number of Ce cations exist not only in the surface layers, but also in the center layers of smaller CeO NCs, which is in contrast to those in larger NCs. Combining with the atomic-scale analysis of the local structure inside the CeO NCs and theoretical calculation on the V forming energy, the mechanism of size effect on the Ce valence states distribution and lattice expansion are elaborated: nano-size effect induces the overall lattice expansion as the size decreased to ≈5 nm; the expanded lattice facilitates the formation of V due to the lower formation energy required for the smaller size, which, in principle, provides a fundamental understanding of the formation and distribution of Ce inside ultrafine CeO NCs.

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The temperature dependence of magnetocrystalline anisotropy constants and the saturation magnetization in a single variant state have been investigated for L10-type Fe60Pt40 bulk single crystal prepared under compressive stress. The uniaxial magnetocrystalline anisotropy constant Ku evaluated from the magnetization curve is 6.9×107ergcm−3 at 5K. The values of the second- and fourth-order magnetocrystalline anisotropy constants K1 and K2 at 5K determined by the Sucksmith–Thompson method are 7.4 and 0.13×107ergcm−3, respectively. Both the values of Ku and K1 decrease with increasing temperature T, while K2 is almost independent of T. The difference between the power law of the Callen and Callen model is described by the dimensionality and the thermal variation of the axial ratio c∕a due to the thermal expansion.