Magnetic vacancies in antiferromagnetic RAg compounds-A PAC study

Magnetic vacancies have been introduced into the (π,π,0)-type antiferromagnetic structure of cubic RX compounds (R=rare earths, X=Ag, Cu) by replacing magnetic R by non-magnetic Y atoms. The magnetic hyperfine interaction resulting from this break of symmetry at the X-site has been investigated in R1−xYxAg; R= Gd, Tb, Dy for Y concentrations 0⩽x⩽0.3 and in Dy0.8Y0.2Cu by perturbed angular correlation (PAC) spectroscopy with 111Cd as probe nucleus. The magnetic hyperfine field produced at 111Cd by one uncompensated nearest neighbor 4f spin is roughly proportional to the spin projection Bhf ∼0.9 (g−1)J [T]. The temperature dependence of the magnetic hyperfine fields reflects the interaction of the 4f charge distribution with the crystal electric field. For R=Gd and Tb, the fraction of probe nuclei with one nearest Y neighbor is much smaller than expected for a statistical distribution of Y on R sites, suggesting that in these R1−xYxAg compounds the 111In/111Cd probe atoms favor Ag sites with eight nearest R neighbors.