Quadrupolar interaction of gadolinium nuclei at the cubic sites of ferromagnetic GdAl 2

Abstract

We show that unresolved quadrupolar splitting is the origin of the large width commonly observed for zero-field NMR lines of Gd on cubic sites in ferromagnetic intermetallic compounds such as GdAl 2. In contrast to earlier published results, this quadrupolar splitting could be well resolved in GdAl 2, even in powder samples provided they were appropriately prepared: e 2 qQ/h is 1.48 (1.34) MHz for 157Gd ( 155Gd) at 4.2 K. The main potential mechanisms for the quadrupolar splitting are discussed. The observed splitting is broken down into different contributions with the aid of their distinctive dependences on temperature and/or magnetization. We conclude that the largest of them, namely the isotropic relativistic quadrupolar interaction, cannot be disregarded in any metallic host. The results reported should also be taken into account for other compounds, rare-earth isotopes and measurement techniques if accurate results for the hyperfine interactions are to be obtained.