Abstract
Perturbed angular correlation spectroscopy has been used to investigate
the combined magnetic and electric hyperfine interaction of the probe
nucleus Cd-111 in ferromagnetically ordered rare earth (R)-dialuminides RAl2 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 Cd-111 PAC spectrum of EuAl2 at 9 K confirms the
antiferromagnetic structure of this compound. (C) 2006 Elsevier B.V. All
rights reserved.
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