Spin and temperature dependence of the magnetic hyperfine field of 111Cd in the rare earth-aluminum Lavesphase compounds RAl2

Abstract Perturbed angular correlation spectroscopy has been used to investigate the combined magnetic and electric hyperfine interaction of the probe nucleus 111 Cd in ferromagnetically ordered rare earth (R)-dialuminides RAl 2 as a function of temperature for the rare earth constituents R=Pr, Nd, Sm, Eu, Tb, Dy, Ho and Er. In compounds with two magnetically non-equivalent Al sites (R=Sm, Tb, Ho, Er), the magnetic hyperfine field was found to be strongly anisotropic. This anisotropy is much greater than the anisotropic dipolar fields, suggesting a contribution of the anisotropic 4f-electron density to magnetic hyperfine field at the closed-shell probe nucleus. The spin dependence of the magnetic hyperfine field reflects a decrease of the effective exchange parameter of the indirect coupling with increasing R atomic number. For the compounds with the R constituents R=Pr, Nd, Tb, Dy and Ho the parameters B 4 , B 6 of the interaction of the crystal field interaction have been determined from the temperature dependence of the magnetic hyperfine field. The 111 Cd PAC spectrum of EuAl 2 at 9 K confirms the antiferromagnetic structure of this compound.