Grain-size-dependent magnetic properties of nanocrystalline Gd

Abstract

Microscopic magnetic and electronic properties of nanocrystalline Gd were studied by $^{155}\mathrm{Gd}$ M\"ossbauer spectroscopy. This technique made it possible to distinguish the microstructure-dependent properties of Gd located in nanocrystal interiors from the properties of Gd in the grain boundaries. For the grain interiors a correlation between the induced magnetic anisotropy and the grain size was observed; this anisotropy can be attributed to the internal pressure resulting from the interface stress of the grain boundaries. The magnetic and electronic structure of the atoms in the grain boundaries differs distinctively from that in the grain interiors: the Gd magnetic moments at the grain boundaries are randomly oriented with respect to the local crystallographic axes, and the density of conduction $s$ electrons is reduced, perhaps as a result of a lower number of Gd nearest neighbors.